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Comparison of Repellency Effect of Mosquito Repellents for DEET, Citronella, and Fennel Oil


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To confirm that Korean Food and Drug Administration (KFDA) guidelines are applicable to test the efficacy of mosquito repellents, these guidelines were used to test the efficacy and complete protection times (CPTs) of three representative mosquito repellents: N,N-diethyl-3-methylbenzamide (DEET), citronella, and fennel oil. The repellency of citronella oil decreased over time, from 97.9% at 0 h to 71.4% at 1 h and 57.7% at 2 h, as did the repellency of fennel oil, from 88.6% at 0 h to 61.2% at 1 h and 47.4% at 2 h. In contrast, the repellency of DEET remained over 90% for 6 h. The CPT of DEET (360 min) was much longer than the CPTs of citronella (10.5 min) and fennel oil (8.4 min). These results did not differ significantly from previous findings, and hence confirm that the KFDA guidelines are applicable for testing the efficacy of mosquito repellents.
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Research Article
Comparison of Repellency Effect of Mosquito Repellents for
DEET, Citronella, and Fennel Oil
Jong Kwang Yoon,1Kang-Chang Kim,1Yeondong Cho,1Yong-Dae Gwon,1
Han Sam Cho,1Yoonki Heo,1Kihoon Park,1Yang-Won Lee,2Mijeong Kim,3
Yu-Kyoung Oh,4and Young Bong Kim1
1Department of Bio-Industrial Technologies, Konkuk University, Seoul 143-701, Republic of Korea
2Department of Dermatology, Konkuk University Hospital, Seoul 143-729, Republic of Korea
3Cosmetics Research Team, Department of Pharmaceutical and Medical Device Research,
Ministry of Food and Drug Safety, Chungcheongbuk-do 363-700, Republic of Korea
4Department of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea
Correspondence should be addressed to Young Bong Kim;
Received  April ; Revised  September ; Accepted  September 
Academic Editor: Dave Chadee
Copyright ©  Jong Kwang Yoon et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
To conrm that Korean Food and Drug Administration (KFDA) guidelines are applicable to test the ecacy of mosquito repellents,
these guidelines were used to test the ecacy and complete protection times (CPTs) of three representative mosquito repellents:
N,N-diethyl--methylbenzamide (DEET), citronella, and fennel oil. e repellency of citronella oil decreased over time, from .%
at  h to .% at  h and .% at  h, as did the repellency of fennel oil, from .% at  h to .% at  h and .% at  h. In contrast,
the repellency of DEET remained over % for h. e CPT of DEET ( min) was much longer than the CPTs of citronella
(. min) and fennel oil (. min). ese results did not dier signicantly from previous ndings, and hence conrm that the
KFDA guidelines are applicable for testing the ecacy of mosquito repellents.
1. Introduction
Insect-borne diseases are a worldwide health problem, espe-
cially in tropical and subtropical climates. Mosquitoes trans-
mit many diseases, including yellow fever, dengue hem-
orrhagic fever, malaria, several forms of encephalitis, and
lariasis []. For example, malaria has been estimated to kill 
million persons per year, including over  million children.
Mosquito repellents may eectively protect humans from
vector-borne diseases as well as other problems caused by
N,N-Diethyl-m-toluamide (DEET) is a readily available
and frequently used mosquito repellent. However, adverse
eects of DEET have been reported, with some being severe
enough to cause sensory disturbances and aect motor
capacity, memory, and learning ability []. In addition,
DEET is not recommended for children, because high con-
centrations of DEET can cause encephalopathy and other side
eects [,].
Botanical mosquito repellents, which cause little risk to
the environment or human health, may be feasible alterna-
tives to synthetic chemical repellents such as DEET. us,
many people prefer to use natural repellents extracted from
plants, such as citronella oil from Cymbopogon nardus,p-
menthane-,-diol (PMD) from Eucalyptus maculata cit-
riodora,andfenneloilfromFoeniculum vulgare [].
Little information is available, however, about the mosquito
repellent activities of these natural and herbal-based sub-
stances. is study evaluated the repellency of commercially
available natural mosquito repellents using the Korean FDA
guidelines and compared their activities with that of %
Hindawi Publishing Corporation
Journal of Parasitology Research
Volume 2015, Article ID 361021, 6 pages
Journal of Parasitology Research
2. Materials and Methods
2.1. Mosquitoes Used in Repellent Tests. Aedes albopictus
(Skuse) mosquitoes were used for repellent testing. Mosquito
larvae were obtained from the Division of Medical Entomol-
ogy of Korea Centers for Disease Control and Prevention
humidity at a dedicated facility of Konkuk University. Adult
mosquitoes were fed and maintained on a % sucrose
solution, as described previously [].
2.2. Repellent Testing. ree kinds of mosquito repellents,
% citronella (California Baby Citronella spray, California
Baby, USA), % fennel oil (Moszero spray, Naturobiotech
Co., Korea), and % DEET (Insectan Spray, Green Cross,
Korea), were purchased. Aliquots of . mL were applied to
volunteers’ forearms to test repellent ecacy [].
2.3. Test Cage. Atestcage(× × cm) was constructed
with a metal frame to make decontamination easier. All sides
were covered with an observable white net to allow viewing.
allow access by a human forearm.
2.4. Patch Tests. A patch containing repellent agent was
applied to clean skin on the volunteer’s forearm and allowed
to remain on the skin for  hours. Volunteers were not
Aer  hours, the patch was removed by medical personnel,
and initial results were determined. e patch region was
marked on the forearm and results were determined  hours
aer initial patch placement.
2.5. Laboratory Tests of Mosquito Repellents. e repellent
tests followed KFDA guidelines modied from WHOPES []
and EPA methods []. Two hundred female mosquitoes (age
– days), which had never received a blood meal, were
placed into each test cage and starved of their sugar diet for
 h before the test.
e arms of each volunteer were washed with unscented
soap, rinsed with water, and dried for  min. A . mL aliquot
of each repellent solution was applied evenly on the right
forearm between the wrist and elbow using a pipette and
arm was placed into a test cage for min and the number of
mosquitoes landing on that arm was counted. If fewer than 
mosquitoes landed on that arm, the volunteer was excluded
from further testing.
Repellent-treated right arms were placed into the test cage
for  min at  h intervals, DEET-treated arms for  h, and arms
treated with fennel or citronella oil for  h. e number of
mosquitoes that landed on or bit that arm was recorded every
Repellency () was calculated using the formula []
where is the number of mosquito bites on the control arm
and the number of bites on the treated arm.
e complete protection time (CPT) was dened as the
determine the CPT of mosquito repellents, the treated right
arm of each volunteer was inserted into the test cage for
 min. If there were no bites, that arm was reinserted at  min
intervals until the rst bite occurred.
2.6. Statistical Analysis. e repellency of the control and
treated arms was compared using -tests, with a value <
. considered statistically signicant. SPSS was used for
statistical analysis. e CPT of DEET repellent was replaced
with a Kaplan-Meier survival function, since there were no
bites over  h.
2.7. Ethics. e study protocol was approved by the IRB
of Konkuk University Hospital (Approval number KUH
). Forty-three volunteers were enrolled, all of whom
provided written informed consent.
3. Results and Discussion
3.1. e Choice of Mosquito Species. To e v a l u a t e t h e e e c -
tiveness of repellent activity against mosquito, we per-
formed preparatory experiments with widespread kinds of
mosquitoes, Culex pipiens, Aedes togoi, and Aedes albopictus.
Culex pipiens, common house mosquito, however, is not
ideal for the repellency test in the laboratory setting because
characteristic. On the other hand, Aedes togoi showed much
less biting activity compared to Aedes albopictus throughout
the experiment setting, which is not optimal to quantify
the biting rate to assess the eect of repellants. us, Aedes
albopictus waschosentoevaluatetheeectofrepellant
activities clearly in the experimental setting.
3.2. Patch Test for Mosquito Repellents. DEET, citronella, and
Initial skin tests on volunteers’ forearms were performed
to assess their allergic responses to the three repellents. As
determined by a dermatologist, none of the volunteers had
allergic reactions at  h and  h (data not shown).
3.3. Repellent Eect for DEET, Citronella, and Fennel Oil. As
hazards by mosquitoes have gradually increased, many kinds
of mosquito repellents have been manufactured to protect
humans against mosquito bites. Because mosquito repellents
have played an important role in protecting humans from
vector-borne diseases caused by mosquitoes, standardized
guidelines are needed to evaluate the ecacy of these repel-
In the United States, for example, repellents are tested
against mosquitoes and other pests according to the guide-
lines of the Environmental Protection Agency (US EPA;
[]) and the American Society for Testing and Materials
(ASTM; []). Although European guidelines have not been
developed, the ecacy of these repellents has been tested
Journal of Parasitology Research
T : Repellency and CPT of % DEET against Aedes albopictus in laboratory test.
Untreated Repel lency (%) (±SE) at hours aer treatment
CPT (min)
h h h h
(%) (%) (%) (%)
V         Unknown
V      
V      
V      
V      Unknown
V     . 
V      Unknown
V      Unknown
V    . . 
V   . . . 
AVG ±. . ±.  ±. . ±. . ±. . ±. . ±. . ±. . ±. ..
e number (𝑁) of mosquitoes landing on arm of each voluntee r was counted per hour for  h. Repell ency (𝑅) was calculated each hour andcomplete protection
time (CPT) was determined by calculating the number of minutes from the time of repellent application to the rst mosquito landing.
according to the guidelines of the World Health Organization
Pesticide Evaluation Scheme (WHOPES; []) and the US
EPA, which are considered the international standard testing
In Korea, the standardized guideline to test the ecacy
of mosquito repellents has been established by modifying the
existing EPA and WHOPES methods in . In this study,
we applied a laboratory test and the semield test (data not
[] and botanical mosquito repellents such as citronella and
fennel oils according to the KFDA guideline.
Table  shows the mean numbers of mosquitoes landing
on untreated (control) and treated forearms of volunteers
over  min. e mean number landing on the untreated
forearms of  volunteers over  min was 16.00 ± 1.71.
Testing of the repellency of treated forearms every hour
for  h showed perfect repellency for % DEET over the
rst  hours. One (V), two (V and V), and six (V,
, and  h, respectively, making the repellency at these
times 99.54 ± 0.46%, 97.89 ± 1.49%, and 90.33 ± 4.16%,
respectively. ese results indicated that % DEET had
DEET (V, V, V, and V) were not bitten by mosquitoes
for  h, so the average CPT for all  volunteers could
not be calculated. us, CPT in this group was estimated
using the Kaplan-Meier survival function, resulting in a
CPT between . and . min at % condence
e use of botanical mosquito repellents has increased
include extracts of basil, citronella, fennel, cedar, cinnamon,
garlic, geranium, lavender, rosemary, thyme, pennyroyal,
peppermint, pine, and verbena oils, which have shown
repellent activity against dierent mosquito species as well as
Aedes albopictus [,]. is study tested the repellency
and CPT of % citronella and fennel oil-containing products
according to KFDA guidelines.
e repellency of % citronella oil was tested in 
volunteers. When their untreated le forearms were exposed
to  mosquitoes for  min, a mean (±SE) of 35.25 ± 2.81
mosquitoes landed.
volunteer was placed into the test cage for  min at  min
intervals until the rst mosquito landed (Table ). Seven
volunteers (V, V, V, V, V, V, and V) were bitten
within the rst min, another  volunteers (V, V, V, V,
min exposure period ( min), and the last two (V and
V) during the third  min exposure ( min). ese results
indicated that the average CPT of citronella oil for these 
volunteers was 10.50 ± 1.20min.
Aer completing the CPTs for each volunteer, repellency
tests were performed at application and at  h and  h aer
treatment (Table ). Repellency at  h,  h, and  h was 97.92±
0.69%, 71.42±3.05%, and 57.73±4.03%, respectively.
Repellency tests of fennel oil were performed on 
volunteers. A mean (±SE) of 21.15 ± 0.36 mosquitoes landed
on their untreated le forearms during exposure to 
mosquitoes for  min (Ta b l e  ).
volunteers (V, V, V, V, V, V, V, V, and V) were
bitten within the rst min, one (V) was bitten during the
second  min exposure period, and three (V, V, and V)
were bitten during the third min exposure period. ese
results indicated that the average CPT of fennel oil for these
 volunteers was 8.38±1.12min.
Repellency tests of fennel oil were performed at applica-
tion andhand hlater. Repellencyat h, h, andhwas
88.57±2.96%, 61.15±3.85%, and 47.36±5.78%, respectively.
Many plant essential oils contain volatile components,
including alkanes, alcohols, aldehydes, terpenoids, and
Journal of Parasitology Research
T : Repellency and CPT of % citronella oil against Aedes albopictus in laboratory test.
Untreated Rep ellency (%) (±SE) at hours aer treatment
CPT (min)
h h h
(%) (%) (%)
V      
V   .  . 
V  .  .  .
V   .  . 
V    .  . 
V   .  . 
V   .  . 
V  . .  .
V     . 
V   .  .
V  .  .  .
V  .  .  .
V  .  .  .
V  ..
V    .   
V   .  . 
V  . .  .
V    .   
V   . . 
V   . . 
AVG .±. . ±. . ±. . ±. . ±. . ±. . ±. . ±.
e number (𝑁) of mosquitoes landing on arm of each voluntee r was counted per hour for  h. Repell ency (𝑅)wascalculatedeachhourandcompleteprotection
time (CPT) was determined by calculating the number of minutes from the time of repellent application to the rst mosquito landing.
T : Repellency and CPT of % fennel oil against Aedes albopictus in laboratory test.
Untreated Repellency (%) (±SE) at hours aer treatment
CPT (min)
h h h
(%) (%) (%)
V  .  .  .
V  .  . .
V   .  .
V     
V   .  . 
V      
V     
V       
V    . 
V  . .  .
V  . . .
V  .   .
AVG . ±. . ±. . ±. . ±. . ±. . ±. . ±. . ±.
e number (𝑁) of mosquitoes landing on arm of each voluntee r was counted per hour for  h. Repell ency (𝑅)wascalculatedeachhourandcompleteprotection
time (CPT) was determined by calculating the number of minutes from the time of repellent application to the rst mosquito landing.
Journal of Parasitology Research
T : Comparative CPT of DEET and citronella oil against mosquito bites.
Product name Active ingredient Percentage (%) CPT (min) Reference (year)
Insectan Spray DEET  .. Yoon et al. () []
( ±.)
Aero Bug O DEET   EPA () []
AquaPel % DEET
Insect Repellent Pump DEET   EPA () []
Spray 
/ DEET   avara et al. () []
OFF! Deep Woods DEET . . (±.) Fradin and Day () []
California Baby Citronella spray Citronella . (±.) in this study
Buzz Away Citronella . (±.) Fradin and Day () []
Complete protection time (CPT) was determined by calculating the number of minutes from the time of repellent application to the rst mosquito landing.
monoterpenoids, with some of these components showing
arepellencyeectinthevaporphase[]. Due to their
volatility, however, these components have a much shorter
protection time against mosquitoes than DEET [,].
erefore, several controlled-release formulations have been
developed to increase the duration of repellency [,
]. erefore, Ecacy Data Sheets used to register repellent
products with the EPA specify CPTs.
Fradin and Day [] conducted the laboratory test with
the method modied from EPA and WHOPES method as
follows.  mosquitoes were placed in a test cage measuring
 cm × cm × cm and volunteers’ arms were inserted
for  min every hour for a total of  h to test repellency.
CPT was determined by inserting volunteers’ arms for  min
every  min for a total of  min until the rst mosquito bite
occurred. Using this method, the mean CPTs of .% DEET
and % citronella were 301.5 ± 37.6 min and 13.5 ± 7.5min,
respectively (Table ).
In comparison, this study used a lower density of
mosquitoes, with  mosquitoes in a cage measuring  cm
× cm × cm, because the lower-density environment
more accurately mimics the biting pressures during outdoor
activities. e repellency and CPT of DEET were assessed
for  min every  h for a total of  hours. In contrast, the
repellency of citronella and fennel oils was tested for  h,
because their repellency was approximately % at  h. e
mean CPTs of DEET and citronella repellent were  min
and . min, respectively, similar to previous ndings [,
]. However, the CPT of % DEET repellents registered
with the EPA was reported to be  min, which diered
from our results (Table ). Since four of our volunteers
(V, V, V, and V) were not bitten by any mosquito
 hours aer DEET treatment, the average CPT would
likely have been longer had the experiment been continued
until each volunteer was bitten. us, the CPT measured
in this study was consistent with that specied by the
e repellency and CPTs of DEET, citronella, and fennel
oil, measured according to KFDA guidelines, were consistent
with previous ndings. KFDA guidelines will therefore be
utilized to evaluate the ecacy of mosquito repellents.
Conflict of Interests
e authors declare that there is no conict of interests
regarding the publication of this paper.
is research was supported by a grant of the Ministry
of Food and Drug Safety (MFDS; KFDA), Korea
Institute of Planning and Evaluation for Technology in Food,
Agriculture, Forestry and Fisheries (IPET; ---
SB), and the Ministry of Trade, Industry & Energy (MI;
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... However, because of its lipophilic nature, DEET can be absorbed by the skin and pass through the cutaneous barrier, reaching deeper layers of the skin and blood vessels [8]. Several studied have reported toxic effects of DEET such as skin rash, seizures, encephalopathy, and central nervous system toxicity [9][10][11]. Therefore, there is a need to develop topical formulations with minimum permeation of DEET and retention of its repellent activity [12]. ...
... The desired characteristics of insect repellents are minimum permeation and sustained repellent activity in the superficial layers of the skin [12]. DEET, an insect repellent, is an oily volatile substance, and direct application of DEET may lead to systemic adverse effects and skin toxicity [9][10][11]. Therefore, solvents that can attenuate the skin penetration of DEET are required. ...
... g/mol and 1.96, respectively, DEET can pass through the cutaneous barrier and be absorbed via the deeper layers into the blood [8]. Furthermore, side effects of DEET, such as central nervous system toxicity, seizures, skin rash, and encephalopathy, have been reported [9][10][11]. Taken together, POE-POP decreased the lipophilic feature of DEET as the logP of DEET in DEET-EPP was significantly lower than that in DEET-E (Fig 1C), and the enhanced hydrophilicity of DEEF formulations attenuated their ability to penetrate into the skin, since skin surfaces such as stratum corneum are hydrophobic. ...
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N,N-diethyl-meta-toluamide (DEET) is a widely used insect repellent, with minimal skin permeation and sustained repellent activity in the superficial layers of the skin. In this study, we prepared a 10% DEET formulation consisting of 40% ethanol with or without 2% poly(oxyethylene)/poly(oxypropylene) butyl ether (POE-POP), an amphiphilic random copolymer. Further, we demonstrated the effects of POE-POP on tensile stress (stickiness), hydrophobicity, skin retention, permeation, and repellent activity of DEET. Stickiness was measured in male ICR mice (7-week old), and skin retention and permeation were evaluated in male Wistar rats (7-week old). In addition, female Aedes albopictus were used to measure the repellent action of DEET. The addition of POE-POP did not affect stickiness, volatility, and degradability but decreased logP and increased viscosity of DEET. Next, we demonstrated the behavior of DEET formulations in the rat skin. POE-POP prolonged the retention of DEET in the superficial layers of the rat skin (skin surface and stratum corneum) and decreased the penetration of DEET into rat skin tissues (epithelium and dermis). The repellent effect of DEET was also enhanced by the addition of POE-POP. However, severe skin damage was not observed after repetitive treatment with DEET formulations containing POE-POP for one month (twice a day). In conclusion, we demonstrated that a 10% DEET formulation consisting of 40% ethanol and 2% POE-POP attenuated the skin penetration and prolonged the repellent action of DEET without causing stickiness and skin damage. We conclude that the combination of ethanol and POE-POP is useful as a safe and effective delivery system for the development of insect repellent formulations containing DEET.
... Another innovative method employs transdermal delivery of vitamin B 1 through patches, effectively repelling Aedes mosquitoes. However, synthetic repellents pose environmental hazards through bioaccumulation, leading to unintended health risks (Dimitroulopoulou et al. 2015, Clem et al. 1993, Miller 1982, Briassoulis et al. 2001,Yoon et al. 2015, Roy et al. 2017,Yazar et al. 2011, Celeiro et al. 2014. To address these concerns, the development of plant-based insect repellents is crucial for sustainable mosquito control. ...
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Dengue fever is a mosquito-borne viral illness that affects over 100 nations around the world, including Africa, America, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. Those who get infected by virus for the second time are at greater risk of having persistent dengue symptoms. Dengue fever has yet to be treated with a long-lasting vaccination or medication. Because of their ease of use, mosquito repellents have become popular as a dengue prevention technique. However, this has resulted in environmental degradation and harm, as well as bioaccumulation and biomagnification of hazardous residues in the ecosystem. Synthetic pesticides have caused a plethora of serious problems that were not foreseen when they were originally introduced. The harm caused by the allopathic medications/synthetic pesticides/chemical mosquito repellents has paved the door to employment of eco-friendly/green approaches in order to reduce dengue cases while protecting the integrity of the nearby environment too. Since the cases of dengue have become rampant these days, hence, starting the medication obtained from green approaches as soon as the disease is detected is advisable. In the present paper, we recommend environmentally friendly dengue management strategies, which, when combined with a reasonable number of vector control approaches, may help to avoid the dengue havoc as well as help in maintaining the integrity of the ecosystem.
... Insect-borne diseases are global health problem, especially in tropical and subtropical climates [1]. Malaria infection is among the most severe public health problem confronting Africa, where Nigeria has the greatest number of cases [2], contributing to a quarter of malaria burden in Africa [3]. ...
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Background: Repeated outbreak of malaria compelled many into the use of mosquito chemical repellents in Africa most populous
... Figure 2. depicts the images of the fabric treated with papaya leaf extract. A test cage (40 × 50 × 40 cm) was fabricated with a card bard and one side is covered with transparent plastic sheet with holes which is for air circulation [15]. The fabric sample is pasted on the wall of one side which is shown in Figure 3. ...
Conference Paper
This research work highlights the functional finishing of cotton fabric in eco friendly way using papaya leaf extract for mosquito repellency. The cotton fabric was treated with the extract of Carica papaya leaf using pad dry cure method by changing the concentration of the natural fixing agent, alum (25% and 50%). The treated fabrics were analyzed for mosquito repellency and wash durability. It is found that the fabric treated with 50% alum has shown excellent mosquito repellency when compared to untreated and 25% alum treated fabrics. Better wash durability was also observed in the 50% alum treated fabric. Further, FTIR test was carried out to analyze the functional groups of treated and untreated fabrics.
... However, it can be absorbed by the skin and pass through the cutaneous barrier, reaching deeper layers and blood vessels, since DEET is a lipophilic feature [8]. Therefore, the presence of DEET in the bloodstream was observed with prolonged exposure and high concentrations and should be avoided by pregnant women, because excessive DEET in blood causes adverse effects, such as central nervous system toxicity, encephalopathy, seizures, and skin rash [9][10][11]. In addition, excessive DEET has also been shown to damage painted surfaces, plastics, leather, and synthetic fabrics [7,11]. ...
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N,N-diethyl-3-toluamide (DEET) is one of the most widely used insect repellents in the world. It was reported that a solution containing 6–30% cyclodextrin (CD) as a solvent instead of ethanol (EtOH) provided an enhancement of the repellent action time duration of the DEET formulation, although the high-dose CD caused stickiness. In order to overcome this shortcoming, we attempted to prepare a 10% DEET formulation using EtOH containing low-dose CDs (β-CD, 2-hydroxypropyl-β-CD (HPβCD), methyl-β-CD, and sulfobutylether-β-CD) as solvents (DEET/EtOH/CD formulations). We determined the CD concentration to be 0.1% in the DEET/EtOH/CD formulations, since the stickiness of 0.1% CDs was not felt (approximately 8 × 10−3 N). The DEET residue on the skin superficial layers was prolonged, and the drug penetration into the skin tissue was decreased by the addition of 0.1% CD. In particular, the retention time and attenuated penetration of DEET on the rat skin treated with the DEET/EtOH/HPβCD formulation was significantly higher in comparison with that of the DEET/EtOH formulation without CD. Moreover, the repellent effect of DEET was more sustained by the addition of 0.1% HPβCD in the study using Aedes albopictus. In conclusion, we found that the DEET/EtOH/HPβCD formulations reduced the skin penetration of DEET and prolonged the repellent action without stickiness.
... Likewise, the similar concentration of Citronella oil with a combination of Tween 80 and Span 80 had 6 h effectivity with high protection power to compete with the protective power of positive control up to 93.29% [22]. The results of the protection power test can be seen as shown in the fig. 4 below. ...
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Objective: This study aims to test the effectiveness of Citronella oil microemulsion as a repellent for the Aedes aegypti mosquito. Methods: The preparation of Citronella oil microemulsion was carried out through a high-speed homogenization technique. The microemulsion was formulated with a base of 100 g, consists of Citronella oil in several concentrations 5%, 10%, and 15%, emulsifier (Tween 80 and Tween 20) 10-20% by weight of citronella oil and 80-90% distilled water, made into six formulas (F). The microemulsions were then evaluated for the organoleptic, pH, and transmittance. Results: Based on the organoleptic test showed that F1 was selected as the best formula, a microemulsion with an active ingredient of Citronella oil in a concentration of 5% and an emulsifier 10%. The average pH was 5.35 according to normal skin pH (4-6.5) and the average size of the microemulsion is 2.42±0.09 µm and the PdI (polydispersity index) is 0.68±0.1. The protection power of F1 repellent was 90%, this result showed a significant difference (p-value of 0.005) as compared to Citronella oil without modification (70%), significantly different (p-value 0.001) with Tween 80–Tween 20 (10%) and not significantly different (p-value 0.145) with chemical repellent Product X (97%). Conclusion: Based on the result, it was concluded that the protective power of Citronella oil Microemulsion F1 was almost like chemical repellent Product X.
Citronella oil, extracted from Cymbopogon species (winterianus and nardus) is a commercially valuable essential oil used in personal-care products and insect repellents. Routine analysis in gas chromatography is incapable of detecting high-boiling adulterants therein. In this study, an HPTLC technique was developed for the absolute quantification of citronellal (characteristic chemical marker) and triglyceride (main constituent of vegetable oil adulterant) in citronella oil for its quality assessment. It was validated in terms of specificity, linearity, sensitivity, accuracy and precision. Further, the developed method was employed to quantify citronellal and triglyceride in twenty commercial samples. The results showed a wide variation in citronellal content (trace to 30.65% w/w) and could differentiate its two chemotypes. Also, it revealed the possibility of vegetable oil adulteration through the detection and quantification of triglyceride in selected samples. It can be a simple and rapid technique for the quality control of citronella oil.
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Tithonia diversifolia is widely used in African traditional medicine for the treatment of a large number of ailments and disorders, including malaria. In the present study, we evaluated the repellent activity of essential oils (EO) of this plant against Anopheles coluzzii, a major vector of malaria in Africa. Fresh leaves of T. diversifolia were used to extract EO, which were used to perform repellency assays in the laboratory and in the field using commercially available N,N-Diethyl-meta-toluamide (DEET) and Cymbopogon (C.) citratus EO as positive controls and vaseline as negative control. The repellency rates and durations of protection of the human volunteers involved were used as measures of repellent activity. Chemical composition of the T. diversifolia EO was established further by gas chromatography coupled with mass spectrometry. The moisture content and oil yield were 81% and 0.02% respectively. A total of 29 compounds in the T. diversifolia EO was identified, with d-limonene (20.1%), α-Copaene (10.3%) and o-Cymene (10.0%) as the most represented. In field studies, the mean time of protection against mosquito bites was significantly lower in T. diversifolia EO-treated volunteers compared to treatments with C. citratus EO (71 min versus 125 min, p = 0.04), but significantly higher when compared with the non-treated volunteers (71 min vs 0.5 min, p = 0.03). The same pattern was found in laboratory repellency assays against A. coluzzii. In contrast, repulsion rates were statistically similar between T. diversifolia EO and positive controls. In conclusion, the study suggests promising repellent potential of leaves of T. diversifolia EO against A. coluzzii.
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Estimation of the efficacy of mosquito repellents requires both laboratory and field tests. The results of field tests are more meaningful, but the safety of volunteers in such tests may be a significant concern. In the current study, we compared tests of mosquito repellent efficacy under semifield conditions in an outdoor enclosure with those under laboratory and field conditions. In this study, we assessed the efficacy of N,N-diethyl-meta-toluamide under laboratory conditions with human volunteers and under semifield and field conditions with Centers for Disease Control and Prevention traps and experimental mice. A semifield test may be a suitable replacement for the more difficult field test for assessment of mosquito repellent efficacy. Semifield tests should be considered when developing new guidelines for testing.
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Background: Individual human subjects are differentially attractive to mosquitoes and other biting insects. Previous investigations have demonstrated that this can be attributed partly to enhanced production of natural repellent chemicals by those individuals that attract few mosquitoes in the laboratory. The most important compounds in this respect include three aldehydes, octanal, nonanal and decanal, and two ketones, 6-methyl-5-hepten-2-one and geranylacetone [(E)-6,10-dimethylundeca-5,9-dien-2-one]. In olfactometer trials, these compounds interfered with attraction of mosquitoes to a host and consequently show promise as novel mosquito repellents. Methods: To test whether these chemicals could provide protection against mosquitoes, laboratory repellency trials were carried out to test the chemicals individually at different concentrations and in different mixtures and ratios with three major disease vectors: Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti. Results: Up to 100% repellency was achieved depending on the type of repellent compound tested, the concentration and the relative composition of the mixture. The greatest effect was observed by mixing together two compounds, 6-methyl-5-hepten-2-one and geranylacetone in a 1:1 ratio. This mixture exceeded the repellency of DEET when presented at low concentrations. The repellent effect of this mixture was maintained over several hours. Altering the ratio of these compounds significantly affected the behavioural response of the mosquitoes, providing evidence for the ability of mosquitoes to detect and respond to specific mixtures and ratios of natural repellent compounds that are associated with host location. Conclusion: The optimum mixture of 6-methyl-5-hepten-2-one and geranylacetone was a 1:1 ratio and this provided the most effective protection against all species of mosquito tested. With further improvements in formulation, selected blends of these compounds have the potential to be exploited and developed as human-derived novel repellents for personal protection.
Six controlled-release personal-use topical insect/arthropod repellent formulations of diethylmethylbenzamide (deet) were evaluated in an environmental chamber on volunteers for repellency against the mosquitoes Aedes aegypti and Ae. taeniorhynchus under three climatic regimens: basic variable high humidity (tropical environment), basic constant high humidity (forested and wet environment) and basic hot (hot-dry environment). The best protection under all the climatic regimens was provided by the Biotek formulation. In a tropical environment, some formulations induced more biting from mosquitoes than the concurrent untreated control in the late hours of the testing. Repellency was not directly related to the deet concentration in the various controlled-release repellent formulations.
Laboratory tests of insect repellents by various different methods showed that An.stephensi Liston was consistently more susceptible than An.gambiae Giles, An.albimanus Wiedemann or An.pulcherrimus Theobald. The six repellents tested were di-ethyl toluamide (deet), di-methyl phthalate (DMP), ethyl-hexanediol, permethrin, citronella and cedarwood oil. Testing systems in which the mosquitoes were presented with a choice gave consistently lower ED50 values than when there was no choice, i.e. the standards of tolerance are not absolute but depend on the options available. In field tests in an experimental hut a curtain with a high dose of di-ethyl toluamide (deet) reduced biting in the hut but had to be re-impregnated frequently. Deet-impregnated anklets gave about 84% protection against Culex quinquefasciatus Say for 80 days after one impregnation, in a trial in which the anklets were brought out of sealed storage and tested for 2 h nightly. Similar protection was found against An.funestus Giles but the protection against An.gambiae s.l., An. coustani Laveran and Mansonia spp. was not as good. There were highly significant differences between the four collectors' mosquito attractiveness but this varied highly significantly between the mosquito species.
Extensive animal testing and 30 years of human experience have established the general safety of DEET when applied episodically to skin or bedclothes. Local and systemic toxic and allergic reactions to DEET have been observed in man. Three weeks prior to admission, for the purpose of self-medication, a 30 year old man began daily applications of the insect repellant, DEET followed by a 1-2 hour period in a light-bulb heated box. Sedation and incoherence were noted for short periods following each application session. Aggressiveness and psychotic ideation led to hospital admission where he displayed psychomotor hyperactivity, rapid and pressured speech, tangentiality, flight of ideas, and grandiose delusions. Treatment was begun with haloperidol. Clinical improvement was complete within 6 days, atypical for classic endogenous mania. Drug and metabolites were identified in the urine more than 2 weeks after the last drug application.
Deet is considered to be the best "all around" insect repellent ever developed and is the most widely used insect repellent in the world. Since its first use in a consumer product in 1956, billions of applications have been made to human skin. Information about the safety of deet comes from the human clinical literature, animal toxicology studies, and poison control centers' experiences with deet. The clinical literature reports the association of deet with neurotoxicity in 14 individuals. Three of the cases resulted in death, whereas all of the other patients completely recovered. The exact role of deet in the toxicity reported is difficult to determine from the reports. Recently reported animal safety studies have examined potential neurotoxicity following multigenerational dosing. Effects on the nervous system were only seen when generalized toxicity was also observed. Thus deet is not a selective neurotoxin. Important information about deet also comes from an investigation into the reports of adverse affects reported to 71 poison control centers in the USA. An important conclusion from this study is that there is no evidence that increasing deet concentration has any effect on the severity of the symptoms reported. The vast majority of reported cases had either no symptoms or ones that resolved rapidly. In conclusion, a thorough examination of all information available indicates that the risk of serious adverse effects following the use of deet is extremely low.