Photoprotection: a Public Awareness

Internet Journal of Medical Update, Vol 3, No. 1, Jan-Jun 2008 Letter to editor

Photoprotection: a public awareness

Dr. (Ms.) Meera Sridhar MD, DVD, DDV

Consultant Dermatologist, Dubai, United Arab Emirates

Sir, earth on a particular day and is a recognized part of the weather report in many countries. Excessive solar ultraviolet radiation exposure of the skin has been associated with several FACTORS AFFECTING THE AMOUNT skin disorders/diseases including premature OF ULTRAVIOLET RADIATIONS aging of the skin and skin cancers. Avoiding REACHING THE EARTH’S SURFACE exposure to sun is the best method but AT A PARTICULAR TIME AND PLACE impractical. Public is informed through UV ARE DEPENDENT ON: Index of the amount of harmful ultraviolet rays 1. Time of the day: Two third of the total reaching the earth and choosing of the right UVR reaches the earth between 10 am and SPF (Sun Protection Factor) is the practical 2 pm of which 10 % is UVB and 90 % and effective approach for photoprotection. UVA. Increasing pollution levels (release of 2. Surface reflection: chlorofluoro carbon compounds) into the Snow and ice reflect 80 % of UVR atmosphere over the last 20 years has resulted Sand reflects 20 % of UVR in gradual depletion of the ozone layer which Most ground surfaces reflect < 10 % in turn has resulted in greater amounts of UV of UVR radiations of the sun reaching the earth’s Water reduces penetration of UVR by surface as also global warming. The sun rays 50 % have been broadly classified into 3 groups 3. Seasonal: Maximum radiation occurs based on the wavelength of the electro during summer and minimal in winter. magnetic waves: Infra red (800 – 1700 nm), 4. Altitude: Every thousand meter above sea Visible light (400 – 800 nm) and Ultraviolet level increases UVR by 10%. (UV) rays (290 – 400 nm). The UV rays are 5. Latitude: Higher irradiance at the further classified as: Equator. 1. UVA (320 - 400 nm, long wave length, 6. Cloud coverage: Complete high cloud UVA1: 340 - 400 nm and UVA2: 320 - coverage reduces surface UVR by 50%. 340 nm) 1: It is responsible for immediate pigment darkening of preformed melanin. PROTECTION FROM SUN: It can cause severe phototoxity in the Sun protection is provided by the following: presence of drugs like psoralens, 1. Skin: The skin is naturally protected from doxycycline, sulfonamides, sulfonylureas the sun’s radiation by the thickness of the and chlorthiazides. epidermis, melanin, natural antioxidants, 2. UVB (290 - 320 nm, mid wave length): DNA repair mechanism, Urocanic acid It causes sunburn. It also stimulates and Fas ligand signaling. melanocytes to make new melanosomes 2. Clothes: The protection achieved by causing a tan. wearing clothes is called ‘Ultraviolet 3. UVC (200 - 290 nm): It is mainly Protection Factor’. Clothes with tighter absorbed by the ozone layer; what reaches weave, darker color, synthetic fibers2 and the earth has germicidal effect. loose fit provide greatest protection. Both UVA and UVB cause DNA damage by Polyester is the best UV absorber, whereas the generation of reactive free oxygen. Though cotton and rayon are the poorest. UVB is mainly responsible for photo ageing, 3. Broad rimmed Hats and Umbrellas . sun burn, carcinogenesis and cataract 4. Window Glass: It provides protection formation, UVA rays also play an additive role from UVB, with tinted glass giving some by production of photoproducts and additional protection from UVA as well. suppressing the immune system. 5. Eye Protection: Wrap around sun glasses Hence there is great need for public awareness that fit close and absorb upto 400 nm in of effect of UV radiations on the skin and the UVA, UVB and blue light range. need for photoprotection. The UV Index is a 6. Use of topical sunscreens: They are used program that informs the public about the to protect the skin from the ultraviolet amount of harmful ultraviolet rays reaching the radiations of the sun. They contain a variety of chemical (organic) and physical

blockers each having differing protective MED on unprotected skin 4. An SPF of 15 range. Most of the chemical sunscreens gives 93% protection and SPF30 gives 97% are UVB blockers like: protection. Sunscreens offer mainly protection Para aminobenzoic acid (oldest against sunburn, the UVA protection provided sunscreen to be used, causes staining by chemical sunscreens being about 10% of of clothes) the UVB rating. The term substantivity refers Padimate O (ester derivative of to a product’s ability to remain effective under PABA & most potent UVB absorber): conditions of prolonged sweating, swimming PABA and its esters are more & exercise. So the patient should select a resistant to water & sweating sunscreen which has an SPF of 15 - 30, has a compared to others broad spectrum of protection against both Octyl Salicylate (octisalate) UVA and UVB radiations, is non-toxic, photo Octocrylene (used with avobenzone stable, water resistant, non staining, helps to improve overall stability) cosmetically acceptable and inexpensive. Phenyl benzimidazole sulfonic acid For ideal protection, the sunscreen should be (ensulizole-is water soluble and hence applied every morning till sunset or half hour less greasy) before sun exposure. It has to be reapplied Benzophenones (oxybenzone absorbs every 2 – 3 hours. Sun screens (even if water UVB and UVA2), anthranilates, resistant) have to be reapplied after half hour avobenzone and Bisethylhexyloxy to 1 hour of being in water. For the sunscreen phenol methoxy phenyl triazene to be effective, sufficient amount (0.5 mm (which gives photo stability to layer) has to be applied on all exposed areas avobenzone) are UVA blockers3. not protected by clothing including pinna and Newer sunscreen like Padimate O & neck. An average adult requires approximately Parsol 1789 (major absorption at 360 35 ml of the sunscreen. nm) provide good UVA absorption. Sunscreen lotions are easy to apply and are Chemical sunscreens can cause photo allergic non greasy. Products with higher SPF are or contact dermatitis. Patients allergic to usually oily. Silicone liquids added to these aminobenzoic acid should use sunscreens reduce the greasiness and increases water containing oxybenzone or cinoxate. resistance. For acne prone individuals, water Benzophenones can cause eye stinging. soluble oil free gel based sunscreen are Physical blockers or chemical free sunscreens preferred. Sticks containing lipid-soluble contain tiny particles which scatter and reflect sunscreens are useful for application over the UV rays and visible range. Coating these small areas like nose, ears and under eyes. particles with silicone helps to absorb free They are most water resistant. Aerosols and oxygen radicals (which may be formed as sprays are easy to use but there may be uneven some energy is absorbed) and is the basis of a distribution and skip areas. Also available are product called Z-cote. Zinc oxide, Titanium lipsticks containing sunscreens 5. Currently dioxide, kaolin and Iron Oxide are physical available sunscreens are not substantive to the sunscreens. They do not cause photo allergic hair which is better protected by use of hat, or contact dermatitis and hence can be used in scarf or umbrella. babies less than 6 months and people with Systemic sunscreens are oral agents that have sensitive skin. Disadvantage is that they may been tried, include PABA, indomethacin, be visible on application (which is being steroids, psoralens, retinol, antimalarials like overcome by use of ultra fine particles) and chloroquine & HCQS and antioxidants. They require repeated application as they are washed are mainly used when there is an underlying off by sweat and cannot be used for skin or systemic disease being caused or swimming. exacerbated by sunlight –e.g. lupus The regular use of sunscreens reduces sun erythematosus, PMLE, actinic keratoses, basal burns and incidents of non melanoma skin cell carinoma etc. cancers. Continuous use of sunscreen may alter Vitamin D synthesis, which can be REFERENCES: compensated by a normal diet. 1. Kenneth A Arndt, Jeffrey T S hsu, Manual of Dermatologic Therapeutics, 7th edition, HOW TO CHOOSE AND APPLY A Wolters Kluwer Health (India) Pvt Ltd, SUNSCREEN: 2007:212-20. SPF value of a sunscreen is the dose of UVR 2. Actinic Keratoses Net, When Sun required to produce one MED on protected Exposure Unavoidable, Think skin after application of the 2mg/cm2 of the Photoprotection - product to the UVR required to produce one

http://www.skincarephysicians.com/actini 5. Stanely B Levy, Sunscreen and ckeratosesnet/photoprotection.html Photoprotection. emedicine 3. Rai R, Srinivas CR. Photoprotection, http://www.emedicine.com/derm/topic510 Indian J Dermatol Venereol Leprol .htm 2007;73;73-9. 4. Fitzpatrick’s Dermatology in General Dr. Meera Sridhar Medicine. 5th edition. New York: PO 325, Dubai, United Arab Emirates McGraw-Hill;1999:2742-63. Email: [email protected]