Content uploaded by Deon Canyon
All content in this area was uploaded by Deon Canyon
Content may be subject to copyright.
72 The Open Dermatology Journal, 2010, 4, 72-76
1874-3722/10 2010 Bentham Open
Indirect Transmission of Head Lice via Inanimate Objects
Deon V. Canyon
and Rick Speare
Anton Breinl Centre for Public Health and Tropical Medicine, James Cook University, Townsville QLD 4811, Australia
Abstract: Whether people can become infected by head lice transferring from inanimate objects is a topic of controversy.
This paper reviews the evidence available from experimental studies in controlled laboratory experiments and data from
field studies. The weight of evidence appears to be against transmission from inanimate objects being significant, and the
promotion of inanimate objects that play an epidemiologically important role in head lice dispersal is not supported by
evidence. We conclude that the control of head lice should focus on the head, not on the environment. However,
additional studies are needed to quantify transmission risk via inanimate objects and the probability that head lice eggs
survive and hatch off-host.
Keywords: Pediculosis, pediculus, transmission, fomites, inanimate objects.
An assessment of transmission risks associated with the
spread of pediculosis is important because the prevalence of
Pediculus capitis, the head louse, has increased throughout
the 1900s . In terms of an infectious disease, when
eradication is difficult or impossible, the next best option is
control. This means interrupting the transmission cycle to
limit the spread of disease agents .
Pediculosis is best managed by the individual or the carer
who must act quickly to address infestation and
transmission. Decreased pediculicide susceptibility and
reinfestation make this difficult. Since insecticide
susceptibility may vary substantially at a neighborhood level
, it is best dealt with by adjusting treatment regimes.
Reinfestation may involve direct transmission from other
people or indirect transmission from inanimate objects.
Direct reinfestation, involving head-to-head transmission, is
highly subject to social factors and is thus difficult to
resolve. Indirect transmission via inanimate objects would be
a more resolvable issue.
This paper focuses on head lice transmission via
inanimate objects. We review the body of knowledge in
support of and against this transmission mode. It should thus
be of practical use to policy developers and any person
dealing with a recurrent pediculosis.
The transmission of head lice by way of inanimate
objects is not a clear-cut topic and there is difficulty in
estimating the importance of direct (person-to-person) vs
indirect (inanimate object-to-head) transmission. Since 10-
20% of the children in most primary schools in most
countries have head lice , a recommendation to change
head lice policy in schools and management practices in the
home can have significant economic implications. Several
head lice scholars have devoted their efforts to determine the
*Address correspondence to this author at the Anton Breinl Centre for
Public Health and Tropical Medicine, James Cook University, Townsville
QLD 4811, Australia; Tel: 0431907814; E-mail: firstname.lastname@example.org
mechanisms involved in P. capitis transmission so that
control programs do not squander limited resources . The
irony in this is that most head lice research is unfunded or
suffers limited funding because head lice do not vector
diseases and are simply considered to be an undesirable pest.
Head lice mythology is strong in developed market
economies and there is an abundance of unconfirmed
suppositions that have inspired studies from different
countries [5-11]. Some of these studies are field-based and
employ epidemiological methods while others are
laboratory-based and involve experimentation under
controlled conditions. Other opinion-based publications
provide little in the way of evidence and yet they put forward
energetic arguments in support of strongly held views. These
scholars and many others speculate as to the principal mode
of transmission with varying conclusions because there is
still a lack of data, and evidence-based results from field and
laboratory sources are often contradictory. While
experimental researchers demonstrate that inanimate objects
are potentially important, the body of epidemiological
evidence concludes that direct transmission from head-to-
head is the primary mechanism.
For many years, the most active proponents of head lice
transmission via inanimate objects have been the
dermatologists Craig N Burkhart and Craig G Burkhart from
the USA, while the most active proponents of direct head
lice transmission have been Rick Speare, Petra Buettner and
Deon Canyon from James Cook University in Australia.
Both sides recognize that transmission from head-to-head
and from inanimate objects occurs, but they differ in their
belief in the extent to which each takes place. The former are
advocates of anecdotal and experimental evidence, but they
do not acknowledge most of the epidemiological and
experimental evidence base produced by the latter and term
it ‘dogma’ . The latter recognize the former and are
careful to include their perspectives and evidence in
Indirect Transmission of Head Lice The Open Dermatology Journal, 2010, Volume 4 73
This article now endeavours to make a careful
assessment of evidence at hand because this is not a simple
academic argument, but one which affects people with
pediculosis and their families. The controversy manifests
itself in significant practical and economic outcomes for the
infected population. The advocates of inanimate objects state
that “louse control measures should ... include ... laundering
of everything within the infested individuals’ bed or
quarantining of such material for 10 days, thorough
vacuuming of floors, carpets, upholstery, with a standard
vacuum cleaner” . Advocates of direct, head-to-head
transmission maintain that these measures are unnecessary,
overly burdensome and pose an economic barrier to the
effective management of head lice in all socio-economic
contexts. Clearly the first approach, that of controlling lice
on inanimate objects, is extremely time-consuming and
costly while the latter approach, that of focusing control
efforts on the head, is not.
EVIDENCE IN SUPPORT OF INANIMATE OBJECTS
Different modes of indirect head lice transmission were
proposed in 2000 by Burkhart and Burkhart who state that
inanimate objects can include :
• Dislodged lice on inanimate objects moving onto a
• Dislodged hairs carrying lice to a new host.
• Wind blowing lice from one location to a new host.
• Static electricity from combing which expels lice into
the air and onto a new host.
In a recent review of fomite transmission by Burkhart
and Burkhart (2007), the only evidence-based results
provided in support of fomite transmission originated from
one experimental laboratory study . This study
investigated fomite transmission in a number of ways.
Firstly, a vacuum cleaner was passed over lice positioned on
combs, towels or fabric to see if they could be dislodged.
This does not approximate any realistic situation so the
results are not very relevant to a realistic discussion.
Secondly, lice were placed on 15 strands of hair and were
subjected to a hair drier for a full minute. This also fails to
correlate with reality because people never blast a hair dryer
onto one spot on the scalp for a full minute. Thirdly, the lice
on the 15 strands of hair were combed. This is nothing new
since we know that combing is effective . Fourthly, the
lice on the 15 strands of hair were stirred in water and were
gently towelled which resulted in transfer to the towel. This
experiment also does not replicate reality where lice have
access to a scalp and will run down a hair shaft onto the
scalp to escape from external interference. Fifthly, a band of
infested hair was placed onto a person’s wrist and covered
with dark cloth. After five minutes, 20% of lice had
transferred onto the cloth. Had this final experiment been
performed using a person’s head, it would have been
relevant. Any head lice researcher knows that lice will never
remain on an arm and will always seek to move upwards
until they reach the head. Thus this entire published study,
which forms the ‘evidence-base’ of the transmission via
inanimate objects theory is little more than a flawed
collection of ill-devised and counter-intuitive experiments.
EVIDENCE AGAINST INANIMATE OBJECTS – SUR-
There are other factors to consider that relate to head-to-
inanimate object transmission and inanimate object-to-head
transmission. One factor of key importance is that
transmission of this nature is subject to the capacity of a
louse to survive off-host long enough to come into contact
with a new host and still have the strength to climb on board.
While body lice may live up to 10 days off a host at 15 °C, 5
days at 24 °C and 3 days at 30 °C , this is not true for
head lice which quickly perish from starvation when
removed from a host [6, 18]. Head lice only survive 9-11
hours at 25-37 °C in low humidity and 10-14 hours in higher
humidity, but can survive up to 44 hours at 15 °C in higher
humidity [6, 18]. Most head lice perish 40 hours post-blood
meal if they do not get another blood meal . Thus the
advice from Burkhart and Burkhart to quarantine the living
quarters of infected people for 10 days  is not based on
How these survival data impact on transmission rates
from one substrate to another, whether living or inanimate,
have not yet been determined by experiment although death
after 2 days will stop any theoretical transmission far short of
a 10-day quarantine period. In addition, fully active lice
usually do not leave the head without any reason. Lice
leaving the head may be close to dying, and it can be
assumed that a high fraction of lice found off-head are not
capable of infesting a person or surviving for very long. Data
are required to confirm this assertion.
Whether or not head lice survival rates on inanimate
objects are low or not, it is possible that gravid females could
lay eggs that could later hatch and infest other hosts.
Questions arising from this are: Do head lice off the host lay
eggs on inanimate objects in nature? If yes, what are the
survival and hatch rates of these eggs? In vivo-reared lice
eggs take 8.4 days (range 6-11) to hatch with a hatch rate of
76% when they are exposed to a human host at night and are
placed in a 20°C rearing chamber during the day. However,
when eggs are exposed to a human for 8 hours each night
they take 15.2 days to hatch and only 58-59% hatch [16, 20].
While there are no available data for survival rates of eggs in
unfavorable off-host circumstances, one may assume that the
egg hatch rates off-host in nature is low due to dehydration.
However, additional experimental evidence is needed to
clarify this point.
EVIDENCE AGAINST INANIMATE OBJECTS –
There are very few well-researched, field studies on the
transmission of head lice via inanimate objects. One such
study, an epidemiological investigation on New York
schoolchildren, examined the sharing of lockers and wall
hooks for winter clothing and headwear as a risk factor for
pediculosis . An association was found, however a
replication of this study in Pennsylvania schools found no
Head lice researchers from the Anton Breinl Centre for
Public Health and Tropical Medicine (ABC) at James Cook
University in Townsville (Australia) conducted a series of
specifically designed field studies to investigate the truth
74 The Open Dermatology Journal, 2010, Volume 4 Canyon and Speare
behind commonly mentioned inanimate objects. Their major,
evidence-based, transmission-related findings related to three
studies on the presence of lice on school hats, school floors
and pillow slips of infested school children.
Articles of Clothing as Inanimate Objects
Hats have always been considered high-risk items. The
general public and even many head lice researchers are of
the opinion that hats and other apparel worn by infested
people harbour lice. For instance, it has been stated that
“Fomite transmission is common with Pediculosis capitis.
The source of transfer is often headwear, shared hats,
brushes, combs, earphones, bedding, upholstered furniture,
and rugs” . The validity of this anecdotal assertion was
tested in a study in which over 1000 hats in four Australian
schools were investigated for lice . No head lice were
found in all these hats and over 5500 head lice were captured
from the heads of surveyed students who were wearing the
very same hats. Thus, the results were 100% conclusive and
found that school hats do not sustain head lice transmission.
In another unpublished study conducted by the authors in a
different primary school, a further 1000 hats were examined
for lice and a single louse was identified on a hat belonging
to a student whose hair had just been treated one hour earlier.
It was assumed that this was a louse not killed by the
treatment and was exhibiting the flee response. These
empirical data demonstrate that the odds of head lice
transmission occurring via transmission by the hats of
children with pediculosis is sufficiently low to be considered
improbable and inconsequential.
In conclusion, the transmission of head lice via inanimate
objects including articles of personal clothing is in fact a
well-established myth. When considering why it is so
entrenched, one can only speculate that it originated from
older generations more familiar with body lice residing in
Floors and Floor Coverings as Inanimate Objects
Another common recommendation by many misinformed
companies, web sites and articles in the popular press is to
treat and clean rugs, carpeting or floors when pediculosis is
found. This recommendation is based on the unsubstantiated
belief that head lice are deposited on these surfaces with
some regularity and would survive in the environment of the
home or school long enough for people to become infested
from this environment. However, no data exist in the
scientific literature to support this.
Transmission of head lice from floors to people makes
little evolutionary or biological sense, and the lack of data to
quantify this potential route of transmission means that
recommendations have not been evidence-based. This idea
was put to the test by ABC researchers who carefully
vacuumed the floors of 118 primary school classrooms in
Australia and searched the contents for any signs of head lice
. A median of only 1.6 g of vacuum debris was obtained
from each classroom prior to evening cleaning by school
janitors. No head lice, parts of head lice or head lice eggs
were found in any of this debris, but all samples contained
parts of insects or occasionally whole insects. Ants and parts
thereof were the most commonly identified insects found.
This was notable because 21% (466 out of 2,230 children)
who spent every school day in these 118 classrooms were
infested with lice. A rather staggering total of 14,033 lice
were captured from these 466 infested students and a mean
intensity of infestation of 30.1 lice per infested child was
calculated. Of the infested students, 58% had less than 10
lice, 35% had 10-99 lice, 8% had 100-499 lice, and one 4
year-old female preschooler had 1,623 lice. One hundred and
eight of the 118 classrooms (91.5%) had at least one student
with active pediculosis and an average of 130 lice per
infested classroom was calculated. Thus, the idea that lice
are inclined to drop of a person’s head onto the floor and that
subsequent transmission takes place from floors to people is
a fictitious myth that has been well and truly debunked. The
risk of acquiring head lice from the floors of school
classrooms is zero and there is no benefit in any control or
cleaning activities to remove head lice from floors.
Bedding as a Source of Head Lice
If head lice contaminate bedding, it would pose a
reinfection threat to people who have just been combed or
treated with pediculicides. It would also pose an infection
threat if other uninfested people were sharing the bed.
To resolve the question of whether or not bedding
becomes infested by head lice leaving their host, researchers
at the ABC investigated the proportion of head lice
populations found on pillow cases of people with head lice,
and tested strategies to kill head lice on pillow cases . To
assess the occurrence of head lice on pillow cases, people
with active pediculosis had their head lice collected and
counted and the pillow case they had used the night before
examined for head lice. To test strategies to kill head lice on
pillow cases, live head lice were experimentally placed in
miniature pillow cases, and the cases subjected to a hot
wash, a cold wash, a hot clothes dryer, and hanging out to
dry on an outdoor clothes line in the sun.
In this study, 48 participants were recruited who were
harbouring 1,845 head lice. Of the 48 pillow cases
investigated, two cases had a single live nymph present and a
third had a single dehydrated nymph. Thus, the occurrence
of overnight live lice transference to pillow cases was 4.2%
and proportionately, 0.1% of the head lice population
actively transferred onto a fomite. The second part of the
study found that heat (hot wash and hot clothes dryer) killed
head lice experimentally placed in pillow cases while cold
wash and hanging pillow cases out to dry did not kill head
This low level of pillow case infestation provides further
good evidence that bedding is an incompetent passive vector
to the overall picture of transmission. Pillow cases do pose a
slight risk for transmission or reinfestation but that risk is
low enough to be considered unimportant compared to other
modes of transmission. While this mode of indirect
transmission is more important if bedding is shared,
changing and washing pillow cases in a situation where
multiple infected and uninfected people are cohabiting will
have minimal impact on transmission since such a small
proportion of the head lice population transfers to bedding,
and bedding is a hostile environment for head lice. The point
is for those advising on the control of head lice to look at the
effectiveness of recommendations. Hence, this paper
commented “Pillowcases pose a risk for re-infection with
Indirect Transmission of Head Lice The Open Dermatology Journal, 2010, Volume 4 75
head lice, but the risk is low, and changing pillowcases is a
reasonable cost-efficient strategy to mimimize this risk.”
Unfortunately, this was the only ABC field study cited by
Burkhart and Burkhart who claimed that it provided
evidence in support of “...the transfer of lice to numerous
objects including hats, upholstery, headphones, and
It is entirely plausible that that head lice transmission
occurs via inanimate objects to a significant extent in certain
circumstances, but little more than anecdotal evidence exists
to confirm this . For instance, one of the authors (DVC)
was once travelling in remote Aboriginal communities in
northern Australia and happened one night to sleep in a
‘men’s house’ with five other men. The author slept on the
left of the group with his head approximately two feet away
from the next person’s head and at no time was his head in
contact with the next person’s head. Nevertheless, the author
found himself infested the following day. No other head-to-
head contact can be recalled before or after this event, which
could have resulted in transmission. Head lice transmission
may thus take place over inanimate objects between people
who share bedding if the distance is small. But, the
magnitude of this needs to be confirmed through appropriate
scientific study. Other studies have found that family size,
overcrowding and sleeping in the same bed can promote
Brushes as Sources of Head Lice
Three epidemiologic studies have demonstrated that there
is no association between head lice presence and the sharing
of combs and brushes, and one found an association [10, 29,
30]. In the latter study, which took place in Canada, no lice
were found on the brushes of 10 children with active
pediculosis . The body of evidence thus suggests that
this mode of transmission is possible, but most likely of little
consequence compared to other modes.
RECOMMENDATIONS FOR FUTURE RESEARCH
As discussed, advice abounds on what to wash and clean
if you have a head lice infestation, but the evidence for these
assertions is anecdotal or based on flawed laboratory studies.
Very little, if any, in the way of supporting field evidence is
presented to back up these assertions. At the heart of the
matter are a number of questions about healthy active head
• How often do healthy head lice become naturally
dislodged from their host?
• What do head lice do when they find themselves off-
• Do head lice on inanimate objects constitute a
significant transmission problem?
• Do head lice actively leave their hosts to wait on
inanimate objects for a chance occurrence with
• Do head lice intentionally traverse inanimate objects
to cross from one host to another in response to
olfactory stimuli emanating from potential hosts?
Do female head lice lay eggs when they are off-host?
Do these eggs survive and hatch?
A comprehensive awareness of the biology and ecology
of P. capitis and the epidemiology of pediculosis leads to the
conclusion that transmission via inanimate objects may
occur, but it is unimportant compared to direct person-to-
person transmission. The emergence of data on transmission
factors over the past decade has definitively enabled
evidence-based head lice researchers to state that direct
person-to-person transmission is the major route. However,
transmission is a product of several inter-related variables,
and physical factors pale into insignificance when compared
to social and behavioural factors. The real problem is not
how head lice transmission occurs, but why it is occurring.
Reinfestation is thus is of greater importance, and future
studies should endeavour to reveal the reasons behind it.
The control of head lice should focus on the head, not on
the environment. Head lice scholars should focus on how to
limit reinfestation rather than providing erroneous control
advice. Schools and other institutions wishing to be
proactive should invest their resources into educational
approaches if they wish to render their mass treatment
campaigns more effective. The promotion of inanimate
objects that play an epidemiologically important role in head
lice dispersal is unsupported by the evidence-base, and any
further support of this mode of transmission needs to be
accompanied by new conclusive evidence from well-
designed laboratory and field studies.
 Gratz NG. Human lice: their prevalence, control and resistance to
insecticides: a review 1985-1997. Geneva: World Health
Organization, Division of Control of Tropical Diseases, WHO
Pesticide Evaluation Scheme, 1997.
 Burkhart CN, Burkhart CG. Fomite transmission in head lice. J Am
Acad Dermatol 2007; 56: 1044-7.
 Canyon DV, Hii JLK. Insecticide susceptibility status of Aedes
aegypti (Diptera: Culicidae) from Townsville. Aust J Entomol
1999; 38: 40-3.
 Burkhart CN, Burkhart CG. The route of head lice transmission
needs enlightenment for proper epidemiologic evaluations. Int J
Dermatol 2000; 39: 878-9.
 Juranek DD. Pediculus capitis in school children. In: Orkin M,
Maibach H, Eds. Cutaneous infestations and insect bites. New
York, NY: Dekker 1985; pp. 199-211.
 Nuttall GHF. The biology of Pediculus humanus. Parasitology
1917; 10: 180-5.
 Mellanby K. Natural population of the head-louse (Pediculus
humanus capitis: Anoplura) on infected children in England.
Parasitology 1943; 34: 180-3.
 Slonka G, McKinley T, McCroan J, et al. Epidemiology of an
outbreak of head lice in Georgia. Am J Trop Med Hyg 1976; 25:
 Sinniah B, Sinniah D, Rajeswari B. Epidemiology of Pediculus
humanus capitis infestation in Malaysian school children. Am J
Trop Med Hyg 1981; 30: 734-8.
 Mumcuoglu K, Miller J, Gofin R, et al. Head lice in Israeli
children: parents' answers to an epidemiological questionnaire. Pub
Health Rev 1990-1991; 18: 335-44.
 Ebomoyi EW. Pediculosis capitis among urban school children in
Ilorin, Nigeria. J Nat Med Assoc 1994; 86: 861-4.
 Heukelbach J, Canyon DV, Speare R. The effect of natural
products on head lice: In vitro tests and clinical evidence. J Ped
Infect Dis 2007; 2: 67-76.
 Heukelbach J, Canyon DV, Oliveira FA, Muller R, Speare R. In
vitro efficacy of over-the-counter botanical pediculicides against
the head louse Pediculus humanus var capitis based on a stringent
standard for mortality assessment. Med Vet Entomol 2008; 22:
76 The Open Dermatology Journal, 2010, Volume 4 Canyon and Speare
 Canyon DV, Speare R. A comparison of botanical and synthetic
substances commonly used to prevent head lice (Pediculus
humanus var. capitis) infestation. Int J Dermatol 2007; 46: 422-6.
 Speare R, Canyon DV, Cahill C, Thomas G. Comparative efficacy
of two nit combs in removing head lice (Pediculus humanus var.
capitis) and their eggs. Int J Dermatol 2007; 46: 1275-8.
 Takano-Lee M, Edman JD, Mullens BA, Clark JM. Transmission
potential of the human head louse, Pediculus capitis (Anoplura:
Pediculidae). Int J Dermatol 2005; 44: 811-6.
 Busvine J. Pediculosis: biology of the parasites. In: Orkin M,
Maibach H, Eds. Cutaneous infestations and insect bites. New
York: Dekker 1985; pp. 163-74.
 Payot F. Contribution a l'etude du Phthirus pubis (Linne, Leach).
Bull Soc Vaud Natl 1920; 53: 127-61.
 Takano-Lee M, Yoon KS, Edman JD, Mullens BA, Clark JM. In
vivo and in vitro rearing of Pediculus humanus capitis (Anoplura:
Pediculidae). J Med Entomol 2003; 40: 628-35.
 Speare R, Cahill C, Thomas G. Head lice on pillows, and strategies
to make a small risk even less. Int J Dermatol 2003; 42: 626-9.
 Speare R, Buettner PG. Hard data needed on head lice
transmission. Int J Dermatol 2000; 39: 877-8.
 Speare R, Thomas G, Cahill C. Head lice are not found on floors in
primary school classrooms. Aust N Z J Public Health 2002; 26:
 Burgess I. Head lice. Clin Evid 2005: 2044-9.
 Andrews JR, Tonkin SL. Scabies and pediculosis in Tokelau Island
children in New Zealand. J R Soc Health 1989; 109: 199-203.
 Kwaku-Kpikpi JE. The incidence of the head louse (Pediculus
humanus capitis) among pupils of two schools in Accra. Trans R
Soc Trop Med Hyg 1982; 76: 378-8.
 Sinniah B, Chandra S, Ramphal L, Senan P. Pediculosis among
rural school children in Kelang, Selangor, Malaysia and their
susceptibility to malathion, carbaryl, perigen and kerosene. J R Soc
Helth 1984; 104: 114-5, 118.
 Jinadu MK. Pediculus humanus capitis among primary school
children in Ife-Ife, Nigeria. J R Soc Health 1985; 105: 25-7.
 Chunge R. A study of head lice among primary school children in
Kenya. Trans Roy Soc Trop Med Hyg 1986; 80: 42-6.
 Chunge R, Scott F, Underwood J, Zavarella K. A review of the
epidemiology, public health importance, treatment and control of
head lice. Can J Public Health 1991; 82: 196-200.
 Chunge RN, Scott FE, Underwood JE, Zavarella KJ. A pilot study
to investigate transmission of headlice. Can J Pub Health 1991; 82:
Received: April 5, 2010 Revised: May 18, 2010 Accepted: May 18, 2010
© Canyon and Speare; Licensee Bentham Open.
This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/
3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.