Update on Photoprotection

Abstract

Photoprotection by sunscreens, clothing and glasses are important to protect the skin against the detrimental effects of sun exposure. In order to achieve complete protection, topical strategies must shield against the range of solar wavelengths ultraviolet A, ultraviolet B, infrared radiation that can damage the skin. To provide the necessary broad spectrum coverage, combinations of chemical and physical UV filters along with molecules that are capable of interfering with and/or preventing the deleterious effects of sunlight are discussed in this review.

Full text

335 Indian Journal of Dermatology 2012; 57(5)
Introduction
Ultraviolet (UV) composes only a small region of the
electromagnetic radiation spectrum and is divided into
three subdivisions: Ultraviolet C (UVC) (200–290
nm), Ultraviolet B (UVB) (290–320 nm), and UVA
(320– 400 nm). Ultraviolet A (UVA) is further divided
into UVA1 (340–400 nm) and UVA2 (320–340 nm).
Ozone in the Earth’s atmosphere absorbs 100% of UVC,
approximately 90% of UVB, and virtually no UVA and
hence depletion of the ozone layer has lead to a substantial
increasein UVtransmission tothe Earth’ssurface.
The understanding of Ultraviolet radiation (UVR) and
its effects on the skin is important. The UV spectrum
causes ageing of the skin, sunburn development, the
production of precancerous and cancerous lesions, and
immunosuppression. Immunosuppressive effects include
suppression of contact hypersensitivity and delayed-type
hypersensitivityandchanges inLangerhans cellfunction. [1]
UVA is associated with ageing effects and produces
pigmentation. It penetrates deeper into the skin layer and
indirectly damages the DNA via the production of radical
oxygen species (ROS). It causes a decrease in Langerhans
cellspresentinthedermis,whereasincreasinginammatory
cells in the dermis.[2] UVA increases the expression of
p53, a tumor suppressor gene,[3] whereas promoting UVB
carcinogenicity and oxidative stress.[4] UVB exposure, on
the other hand, causes sunburns and DNA strand breaks.
UVB produces pyrimidine dimer mutations, which are
stronglyassociated withnonmelanomaskincancers.[4]
For many years the focus of research and protective
strategies, has been centered on the UV part of sunlight,
because their relatively high photon energy causes
macroscopic skin changes that are visible even after a
short duration of exposure resulting in accelerated skin
ageing and contributing to the development of cancer. UV
radiation only accounts for approximately 7% of the sun’s
energy[5] but InfraredA (IRA) (760–1440 nm) can also act
as a damaging environmental factor to skin through its
ability to result in alterations in gene expression of skin
cells at multiple points,[6] resulting in accelerated skin
ageing[7,8]and contributingto thedevelopmentofcancer.[9]
The effect of visible light on the skin has received very
little attention, compared with UV radiation and its effects
on the skin are probably less important than the role of
UV radiation. However, visible light sensitivity is an
important phenomenon in diseases such as porphyria, solar
urticaria, and other idiopathic photodermatoses such as
polymorphouslighteruption.
Photoprotection
Modern topical photoprotection involves both primary
protective factors (sunscreens) that absorb or reect
UV radiation and secondary factors (e.g., antioxidants,
osmolytes, and DNA repair enzymes) that can disrupt
the photochemical cascade triggered by UV-penetration,
therebylimiting skindamage.
Sunscreens
Sunscreens have been divided into chemical absorbers
(organic) and physical blockers (inorganic) on the basis
of their mechanism of action. Chemical sunscreens
are generally aromatic compounds conjugated with
a carbonyl group. This general structure allows the
Address for correspondence: Dr. Reena Rai, Department of Dermatology,
PSG Hospitals, Coimbatore, India. E-mail: drreena_rai@yahoo.co.in
Access this article online
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Website: www.e-ijd.org
DOI: 10.4103/0019-5154.100472
Update on Photoprotection
Reena Rai, Shanmuga Sekar C, Srinivas CR
Department of Dermatology, PSG Hospitals, Coimbatore, India
Abstract
Photoprotectionbysunscreens, clothingandglasses areimportantto protectthe skin againstthe detrimentaleffectsof sunexposure. In
order to achieve complete protection, topical strategies must shield against the range of solar wavelengths ultraviolet A, ultraviolet B,
infrared radiation that can damage the skin. To provide the necessary broad spectrum coverage, combinations of chemical and physical
UVlters alongwith moleculesthat arecapable ofinterfering withand/or preventingthe deleteriouseffects ofsunlight arediscussed in
thisreview.
Key Words: Photoprotection, sunscreens, uv radiation
CME Article
What was known?
Modern topical photoprotection involves both primary protective factors
(sunscreens) that absorb or reect. UV radiation and secondary factors
(e.g., antioxidants, osmolytes, and DNA repair enzymes) that can disrupt the
photochemical cascade triggered by UV-penetration.
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336Indian Journal of Dermatology 2012; 57(5)
Rai, et al.: Photoprotection
molecule to absorb high-energy UV rays and release
the energy as lower-energy rays, thereby preventing the
skin-damaging UV rays from reaching the skin. Physical
blockers or nonchemical sunscreens reect or scatter
UVR. They contain inert minerals such as titanium
dioxide or zinc oxide. Organic are either UVA or UVB
blockers[Table1].
UV B blockers
Aminobenzoates
PadimateOis themostpotent UV-B absorber. Thedecline
in its use, along with the demand for higher sun protection
factor (SPF) products have led to the incorporation of
multiple active ingredients into a single product to achieve
the desired SPF, replacing single Para amino benzoic acid
(PABA)esters.
Cinnamates
The cinnamates have largely replaced PABA derivatives
as the next most potent UVB absorbers. They are
octinoxate (octyl methoxycinnamate [OMC]) and
cinoxate (2-ethoxyethyl-methoxycinnamate). OMC is a
potent UVB absorber and is the most frequently used
sunscreen ingredient. The efcacy of OMC can be further
increased when encapsulated in polymethyl methacrylate
microsphere.[10]
Salicylates
Salicylates are weak UVB absorbers and they are generally
used in combination with other UV lters. Both octisalate
and homosalate are water insoluble that leads to their high
substantivity, which is the ability to retain its effectiveness
afterexposuretowaterand perspiration.Trolaminesalicylate
is water soluble and has been used in hair products. These
compounds can also play a minor role to stabilize and
preventphotodegradation ofother sunscreeningredients.[11]
Octocrylene
The absorption prole of octocrylene spans from 290 to
360nmwithpeakabsorptionat307nm.Thecompoundhas
anexcellent safetyprole withlowirritation,phototoxicity,
and photoallergic potential.[12] Octocrylene may be used in
combination with other UV absorbers to achieve higher
SPFformulas andtoaddstability.
Ensulizole
Ensulizole or phenylbenzimidazole sulfonic acid is water
soluble, and it is used in products formulated to feel lighter
and less oily, such as daily use cosmetic moisturizers.
It is a selective UVB lter, allowing almost all UVA
transmission.
Ultraviolet A
Benzophenones
Although benzophenones are primarily UVB absorbers,
oxybenzone absorbs well through UVA II and can be
considered a broad-spectrum absorber. It signicantly
augments UVB protection when used in a given formula.
Oxybenzone has the highest incidence of contact and
photocontact dermatitis of all sunscreens, and these
reactionsare intensiedby exposureto sunorheat.[13]
Benzophenones have poor substantivity, but uptake of the
molecules is detectable in the blood and urine after topical
application. However, the systemic absorption seems to be
of little biological consequence.[14] The molecules become
unstable with UV exposure via oxidation reactions and
consumptionof antioxidantreserves.[11]
Oxybenzone is not photostable and can generate oxygen
radicals upon UV exposure.[15] There is a concern about
its endocrine and carcinogenic effect even though current
scienticstudies havenotsupportedthisfears.[16]
Anthranilates
AnthranilatesareweakUVBlters,andtheyabsorbmainly
inthenear UVAportion of thespectrum.Anthranilatesare
less effective in this range than benzophenones, and they
areless widelyused.
Avobenzone
Butyl methoxydibenzoylmethane or avobenzone provides
superior protection through a large portion of the UVA
range, including UVA I. Despite its efcacy and broad
spectrum, avobenzone is intrinsically photounstable and
signicant photodegradation can occur with a loss of
50–90% of molecules after 1 hour of UV exposure.[17] To
increase the photostability of avobenzone, molecules such
Table 1: Sunscreens and their absorption spectra
Organic lters Sunscreen ingredients Absorption (nm)
Aminobenzoates PABA 283-289
Padimate O 290-310
Anthralates Meradimate 286,335
Cinnamates Octinoxate 311
Cinoxate 289
Salicylates Octisalate 307
Homosalate 306
Trolamine Salicylate 260-355
Benzophenones Oxybenzone 288,325
Sulisobenzone 288,366
Dioxybenzone 288,352
Dibenzoylmethane Avobenzone 360
Camphor Ecamsule 345
Miscellaneous Octocrylene 303
Ensulizole 310
Methylene-bis-benzotr
iazolyltetramethylbuty
lphenol
303,360
Bis-ethylhexyloxyph
enolmethoxyphenyltr
iazine
280-380
Octyltriazone 314
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337 Indian Journal of Dermatology 2012; 57(5)
Rai, et al.: Photoprotection
as UV absorber (e.g., octocrylene) and non-UV lter (e.g.,
diethylhexyl2, 6-napththalate)are added.
Ecamsule
Terephthalylidene dicamphor sulfonic acid or Mexoryl
SX provides protection within the near UVA range. The
compound is photostable, water resistant, and has low
systemicabsorption.
Methylene-bis-benzotriazolyl tetramethylbutylphenol
(MBBT)
Itisabroadspectrumsunscreen,decreasingUVAmorethan
UVB transmission. This molecule offers a broad spectrum
coverage with two absorption peaks at 303 and 360 nm.
The molecule size is large, minimizing the opportunity for
systemic absorption or endocrine-like effects. It acts as a
hybridbetween organicandinorganiclters,combiningthe
micronizedparticletechnologyofinorganicUV lterswith
an organic molecule and together, these properties serve to
absorb,scatter,andreectUVR.
Bis-ethylhexyloxyphenol methoxyphenyl triazine
(BEMT)
It has a broad spectrum of coverage from 280 to 380 nm
and is photostable. It is also advantageous for a lack of
endocrine-likeeffects.[18]
Hydroxybenzotriazoles class: Drometriazole trisiloxane
Drometriazole trisiloxane (DTB) belongs to the class of
hydroxybenzotriazole molecules. It has broad-spectrum
coverageand isphotostable.
Inorganic sunscreens
Inorganic sunscreens or physical blockersscatter or reect
UV rays
Some of the original sunblocks were opaque formulations
reectingor scatteringUVR.Poorcosmeticacceptance had
limited the widespread use until micro sized forms became
available,also knownasinorganicparticulate sunscreens.
Titanium dioxide
Titanium dioxide is a broad-spectrum UV lter that does
not penetrate the stratum corneum. It has undergone a
processofmicronization for improvedcosmesis. Microne
titanium dioxide provides photoprotection against UVB and
UVA II (315–340 nm)[18] but lacks coverage within UVA1
(340–400nm).
Zinc oxide
Zinc oxide is a safe and effective ingredient in photoprotective
products. It is photostable, nonphotoreactive,[19] and
nonphotocatalytic.[12] It has little potential for irritation or
sensitization.Smaller,micronized zincoxideisconsideredas
abroad-spectrumUVprotectant.Althoughnotasefcientin
the UVB range as titanium dioxide, this inorganic UV lter
covers predominately the UVA spectra, with protection into
UVA1. Zinc oxide is also considered inferior as a UV lter
totheorganicsunscreens.[12]
Secondary photoprotection
Secondary photoprotection involves the use of active agents
to counteract the inherent photochemical processes that can
induce DNA damage in skin cells. It may be achieved by
antioxidants, osmolytes, and DNA repair enzymes,[20,21]
(e.g.,photolyaseandT4 endonucleaseV).
UVA damages the skin tissue through reactive oxygen
species (ROS) production, and these radicals are neutralized
by the body’s innate defense mechanism through a
series of enzymatic (e.g., superoxide dismutase, catalase,
glutathione reductase, and peroxidase) and nonenzymatic
antioxidants (AOs). When the buildup of ROS from UV
and environmental pollutions exhausts the enzymatic
machinery and depletes the AOs reservoir, damage to the
DNA, lipid membrane, and proteins can occur. Topical
AOs exert their effect inside the cells and can reverse this
shortage.Furthermore,once penetratedthrough thestratum
corneum, they may remain active for several days.[22] The
antioxidants have also been shown to protect against Near
infrared radiation (IRA) and hence they are important for
theircentral roleinIRAinducedadverseeffects.[7,23]
Antioxidants that are used in sunscreens and cosmetic
products are vitamins and polyphenols. Vitamins
formulated in sunscreens are water soluble vitamin C
and lipophilic vitamin E. Application of L-ascorbic acid
has shown to protect UV-related damage as measured
by erythema or sun burn cells.[24] Topical application of
a-tocopherol has demonstrated a number of protective
effects including reduction in erythema,[25] photoaging,[26]
photocarcinogenesis,[26]and immunosuppression.[27]
Silymarin
Silymarin is derived from the milk thistle plant, Silybum
marianum. This avonoid has strong AO effects capable
of scavenging ROS and preventing lipid and lipoprotein
oxidation. Topical silymarin has been shown to inhibit
UVB-induced sunburn cells, prevent UVB induced
pyrimidine dimers, and reduce the number of UVB-induced
tumorsin mice.[28]
Green tea polyphenols
Green tea contains a rich level of polyphenols and as
AOs, tea polyphenols are more potent than vitamins C
and E. They are capable of scavenging singlet oxygen,
superoxide radicals, hydroxyl radicals, peroxyl radicals,
and hydrogen peroxide. Aside from the AO functions,
tea polyphenols also have antiinammatory and
anticarcinogeniceffects.[29]
Osmolytes
Osmolytes are small molecules that control and stabilize the
cellular environment by regulating hydration and responses
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338Indian Journal of Dermatology 2012; 57(5)
Rai, et al.: Photoprotection
tostressconditions.Osmolytes(compatibleorganicsolutes)
are not only utilized by cells to control cell volumes, but
they have been identied as integral parts of the cellular
defense against environmental noxae. The osmolytes
taurine[30] and ectoine[31] have been demonstrated to protect
against detrimental UV effects and are incorporated into
severalcommerciallyavailablesunscreens.
Photoprotection by clothing
Wearing clothing has been emphasized as an important
means of photoprotection. Compared with sunscreens,
clothing has a number of advantages. Clothing and hats
offer a balanced and uniformed protection for both UVA
and UVB but most of the sunscreens deliver more UVB
protection.Clothingand hatsoffer morereliableprotection
as long as users remember to wear them. By contrast,
a user needs to apply sunscreens 30 minutes prior going
outdoors and reapply them every 2 hours, and the degree of
protection offered by sunscreens depends on application of
thecorrectamountoftheproduct.
The protection offered by clothing is measured by
ultravioletprotection factor(UPF).
UPF is dened as the ratio of average effective UV
irradiance transmitted without fabric to the average
effective UV irradiance transmitted through fabric. Fabrics
are placed into classes based on the calculated label UPF
value.[32] The good protection is composed of fabrics with
labelUPF valueof15–24,thevery goodprotectionclassis
composed of fabrics with label UPF values of 40–50, and
50+(the highestvaluepermittedonalabel).
Polyester has the best UV absorbing capacity while
cotton has the least.[33] The use of optical whitening agents
can likewise increase UPF through their uorescent-
like properties (re-emitting absorbed UVR in the visible
spectrum); however, this augmented protection is limited
bypartial UVBcoverage.[34]
To conclude wearing a colored loose tting fabric offers
thebestphotoprotectionfrom clothing.
Photoprotection by glasses
UVR ltration by sunglasses is important because it
prevents the development of certain ocular disorders
including cancers of the eye/eyelid, cataracts, and possibly
age-related macular degeneration. Sunglass effectiveness,
on the other hand, depends on factors such as size, shape,
UV blocking ability, and reection from the back of
the lens.[13] The American Academy of Ophthalmology
recommends that sunglasses block 99% of UVR, and those
that comply with this standard are labeled accordingly. [35]
The United States, the United Kingdom, Germany,
Australia, and France have standards for UV protective
sunglasses. In our country we do not have any standard
guidelines for sunglasses. Dongre et al.[36] studied the UV
protective properties of sunglasses in UV phototherapy
chambers and reported that the mean reduction in UVA
penetration was 84.89% and that in UVB penetration was
68.74%. Thirteen sunglasses (four branded ones and nine
unbranded ones) provided greater than 80% reduction in
UVA rays and hence wearing sunglasses during outdoor
workcouldprovideadequatesunprotection.
Newer technologies in sunscreens
Various technologies are used to make the sunscreens more
effectiveand cosmeticallyacceptable.
Nanotechnology in sunscreens
Nanomaterials are ultrane single particles with a
diameter less than 100 nm.[37] Nanotechnology is currently
being developed for diagnosis and labeling, targeting of
drugs, and immunotherapy. In 1999 the Food and Drug
Administration (FDA) allowed the use of nanoparticles in
sunscreens. The use of nanoparticles improves the texture
andcosmeticappealof sunscreens.
The traditionally used physical blockers such as titanium
dioxide and zinc oxide are thicker formulations and hence
were not cosmetically acceptable. The newer sunscreens
containing nanosized products of titanium dioxide and
zinc oxidehave replaced the older formulations and these
ultraneparticlesblendwiththeskin andare cosmetically
acceptable.
The use of nanotechnology has revolutionized the
eld of sunscreens but toxicologists believe that the
nanoparticles can be potentially harmful. The penetration
of nanoparticles are limited by their molecular size.
Lademann et al.
[38] investigated the penetration of titanium
dioxide microparticles into the horny layer and the orice
of the hair follicle in human skin and found that the
amount of titanium dioxide found in any given follicle
wasless than1%oftheapplied totalamountofsunscreen.
Penetration of microparticles into the viable skin tissue
wasnot detected.
Thelarger surfacearea ofthe ultraneparticlescanprovide
an interface for catalytic reactions which can produce
free radicals and damages the proteins, lipids and DNA.
Nanoparticles can also form complexes with proteins which
canescapeimmunologicalsurveillance.[39] The nanoparticle–
protein complexes can also act as haptens, which can
induce autoimmune diseases.[40] Further studies are required
todeterminethesafetyofnanosizedparticlesunscreens.
Sunspheres
This technology consists of styrene/acrylate polymers
that form a nonabsorbable material. These spheres are
then lled with water, which upon application to the skin,
escapesleavingahollowshellcapableoflightscattering.
These hollow spheres increase the surface area contact of
UV lters with incoming UVR, increasing the effective
SPFof asunscreenby50–70%.
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339 Indian Journal of Dermatology 2012; 57(5)
Rai, et al.: Photoprotection
Controversial aspects of sunscreens
There are certain controversies regarding the
usage of sunscreens.
Schulmpf et al.[41] noted that benzophenone, 3-benzylidene
camphor, 4-methylbenzylidene camphor, and octyl-
methoxycinnamate increased uterine weight in immature
rats. Scientic Committee of Cosmetic Products and Non-
Food Products, an European committee based in Belgium,
noted that the relative estrogenic potencies of UV sunscreen
products, both in vitro and in vivo, were about 1 million
lessthanestradiol,thepositivecontrolsubstance.[11] Thyroid
weight was increased by higher 4-methylbenzylidene
camphor doses. The UV lter benzophenone 2 inactivates
human recombinant thyroperoxidase in vitro and disturbs
thyroid hormone homeostasis in rats.[42] The endocrine
activity of sunscreens is controversial and future studies are
warranted.
There are conicting reports regarding the efcacy of
sunscreens against the immunosuppressive effects of UV
and it has been shown that the application of a sunscreen
with a higher SPF can decrease the systemic UVB induced
suppressionofcontacthypersensitivityinhuman skin.[43]
Regular sunscreen application can delay[44] or prevent the
onset of skin tumors in mice, while other reports also
indicateitsefcacyagainstprecanceroushumanlesions.[45]
There is also a risk that the regular use of sunscreen could
lead to decreased vitamin D levels in the elderly[46]through
the decreased UVB-induced cutaneous synthesis of
previtaminD3; butthe riskisminimalintropicalclimate.
Measuring sunscreen efcacy
The UVB protection offered by sunscreens is measured by
theSPFandsubstanstivity.
Sun protection factor
SPF is a numerical rating system to indicate the degree of
protectionprovidedbyasuncareproduct.Itisdenedas
the ratio of the least amount of UV energy (UVB) required
to produce minimal erythema on sunscreen-protected skin
to the amount of energy required to produce the same
erythema on unprotected skin. As UVB is approximately
1000 times more erythemogenic as compared with UVA,
theSPF islargelyameasureofprotectionagainstUVB.
Substantivity
This term is dened as the ability of a sunscreen to
maintain efcacy and withstand adverse conditions such
as exposure to water and sweat.[47] The FDA also denes
theterms‘water-resistant’and ‘verywaterresistant.’Water
resistance is dened as the ability of a sunscreen to retain
its photoprotective properties following two 20-minute
intervals (40 minutes total) of moderate activity in water
immersion. Very water resistant is dened by doubling
aquatic activity time to four 20-minute activity intervals (80
minutes total).[48] Interestingly, the FDA permits products
labeled as water resistant or very water resistant to be
groupedtogetherunderthesameterm‘sweatresistant.’[49]
Assessing UVA protection
The in vivo testing methods are immediate pigment
darkening (IPD), persistent pigment darkening (PPD), and
theprotectionfactor inthe UVA(PFA).These methodsare
expensive, and require unacceptably high UVA exposure to
human subjects. IPD describes the immediate gray-brown
pigmentation of the skin as caused by the oxidation of
preformed melanosomes in the skin. IPD peaks within the
rst minute after UVAexposure.[13] The transient nature of
IPD which requires immediate testing makes it a less than
idealmeasurement toolof UVAprotection.
The PPD method, currently used in Austria and Japan,
evaluates sunscreen effectiveness against UVA by
measuring melanin photo-oxidation postexposure.[50] PPD
is measured between 2 and 24 hours following irradiation
and has the added benet of simultaneously evaluating
sunscreen photostability. However, PPD requires subjects
be exposed to high-intensity lamps for long periods of time
(upto1hour).
The PFA has a less inclusive endpoint following UVA
irradiation, measuring either erythema or pigmentation
(tanning). Like PPD, it is evaluated 24 hours after light
exposure.
In vitro models of evaluating UVA protection present a
uniquesetofsolutionsandchallenges.Unlike in vivo testing,
laboratory testing may be a more efcient, reproducible,
cost-effective testing method. In vitro method of UVA
protection is measured by the Diffey critical wavelength
determination.[51] In this method, the sunscreen agent is
applied to a substrate, and the UV absorbance is measured
alongacontinuumfrom290 to400nm.Itisthencalculated
as ‘the wavelength below which 90% of sunscreen’s UV
absorbance occurs.[13,49] The UK uses a variation of this in
vitro testcalled the Boots Star rating. The Star system is a
ratio of two in vitro tests: the measurement of a product’s
UVAabsorbancetoitsUVBabsorbance.
Ideal Sunscreen
The ideal sunscreen should rst and foremost provide
superior efcacy with broad-spectrum coverage,
photostability, and high substantivity. It should have an
appealing feel and uniformly coat the skin surface. Lastly,
a sunscreen should be supplied at a reasonable cost to the
consumer.
General application recommendations
Application density
The average adult should apply approximately 35 mL
for full-body application to cover an area of 1.73 m.[2,52]
In addition to application density, consumers should be
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340Indian Journal of Dermatology 2012; 57(5)
Rai, et al.: Photoprotection
educated on overall guidelines for sunscreen use. The
sun-protective clothing is a powerful adjunct to topical
sunscreens.Clothingshould cover skinrst, and sunscreen
should be used under clothing as well as to exposed skin.
Individuals should avoid time spent outdoors between 10
am and 4 pm. Since the time zones and daylight savings
time separates solar noon from the ascribed noon time,[53]
Ting offers a convenient rule of thumb: ‘If one’s shadow
islongerthan oneistall,’avoid prolongedoutsideactivity.
Eide[54] refers to this as the ‘shadow rule’ and patients
should avoid this time, when the solar zenith is less than
45degrees.
Reapplication
Reapplying sunscreen after initial application is another
important step in effective sun safety. Individuals should
applyarst coat ofsunscreen half anhourbefore walking
out of the door. A second application approximately 20
minutes after initial application is estimated to prevent an
additional65–80%ofUVtransmission[55] and corrects areas
ofmisapplication.[56]Sunscreen should be reapplied every 2
hours and more frequently during activity-lled days. Up
to 85% of a product can be removed by towel drying, so
reapplication should occur after swimming, sweating, or
anyotherrigorousactivity.
Conclusion
Complete topical photoprotection can only be obtained
if a sunscreen formula protects against UVB, UVA, and
IRA. The role of additional wavelengths contributing to
skin damage is currently not known. In order to achieve
a near complete broad spectrum protection as possible,
a sunscreen should incorporate molecules of both of
primary and secondary photoprotection along with other
photoprotectivemeasures.
What is new?
Complete topical photoprotection can only be obtained if a sunscreen formula
protects against UVB, UVA, and IRA.
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How to cite this article: Rai R, Shanmuga SC, Srinivas CR. Update on
photoprotection. Indian J Dermatol 2012;57:335-42.
Received: April 2011. Accepted: December 2011.
Source of support: Nil, Conict of Interest: Nil.
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342Indian Journal of Dermatology 2012; 57(5)
Rai, et al.: Photoprotection
Questions
MCQ
1 The effects of UVA include
a) ageing effects and pigmentation
b) production of radical oxygen species
c) decrease in Langerhans cells
d) increases the expression of p53, a tumor suppressor
gene
e) all of the above
2. AllareUVBblockersexcept
a) octinoxate
b) octisalate
c) avobenzone
d) octocrylene
3. The substance used to stabilize water insoluble
sunscreen ingredients is
a) meridimate
b) trolamine salicylate
c) ecamsule
d) ensulizole
4. Secondaryphotoprotection includesallexcept
a) Antioxidants
b) Osmolytes
c) DNA repair enzymes
 d) Inorganicsunscreens
5. TheclothingmaterialwithbestUVabsorbingcapacity
is
a) Cotton
 b) Wool
c) Polyester
d) Silk
6. Theadverse effectsof nanoparticlesinclude
a) interface for catalytic reactions
b) complexes with proteins which can escape
immunological surveillance
 c) inductionof autoimmunediseases.
d) all of the above
7. The UV lter which disturbs thyroid hormone
homeostasis in rats is
a) octylmethoxycinnamate
b) benzophenones
c) PABA
d) homosalate
8. The in vivo methods for measuring UVA protection
are all except
 a) immediatepigmentdarkening (IPD)
b) persistent pigment darkening (PPD)
c) protection factor in the UVA (PFA)
d) sun protection factor (SPF)
9. The average adult should apply approximately
---mLforfull-bodyapplicationtocoveranareaof 1.73
m2
a) 25 ml
b) 30 ml
c) 35ml
 d) 40ml
10. Completetopicalphotoprotectioncanonlybeobtained
if a sunscreen formula protects against
a) UVB
b) UVA
 c) IRA
d) all of the above
Answers
1.(e) 2. (c) 3. (b) 4.(d) 5.  (c) 
6.(d) 7.(b) 8.(d) 9.(c) 10. (d)
DUPLICATE SUBMISSION
Itcametoournotice thatsomeauthorshavesubmittedsamearticlessimultaneously totwo(ormore)differentjournals.
Whilesubmittinganyarticlethe author/sgive/s anundertaking thatthespecicarticleis notsubmitted elsewhereoris
notunderconsiderationforpublicationby anyotherjournal.
So, simultaneous or parallel submission of same article to different journals cannot be taken as an innocent and
inadvertenterror butan intentional,unethical anderroneouscommission.
Thisisanunacceptableactonbehalfofanyauthor.
Ourjournalrecognizesthese asacademicdishonestyandfollowsapolicyofzerotoleranceinmatterslikethese.
– Koushik Lahiri
 Editor,IJD®
Announcement
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