sunscreen.pptx

Use of Sunscreen in dermatology

1. Sunscreens DR. SHRADDHA KALE

2. Electromagnetic spectrum or solar spectrum of the Sun 400nm-700 nm 700-2500nm

3. Near UVA Far UVA 290nm (<9% of total solar irradiance) (100-400nm)

4. Depth of Penetration of UV Light depends on its wavelength (i.e., longer the wavelength , deeper the penetration) UVA, VL, and IR (longer wavelengths) penetrate deeper (up to the subcutaneous tissue) than UVB (shorter )

5. Photobiological Reactions Biological effects of UVR are more pronounced with the light of shorter wavelength as it contains a high quantum of energy. To produce the same degree of erythema , the dose of UVA required is 1000 times higher than that of UVB while VL fails to produce erythema even at that dose.

6. DEFINITION Sunscreens are agents that alter the effects of UV radiation on the skin by absorption or reflection of part of the incident radiation

7. Sunscreen Indications Protection from ultraviolet radiation to prevent the following: Sunburn- FDA Approved Skin or lip damage, freckling, skin discoloration—FDA-approved Skin aging—FDA-approved Skin cancer—FDA-approved Phototoxic or photoallergic drug reactions Photosensitivity diseases Photoaggravated dermatoses

8. Contraindications Known sensitivity to any active sunscreen ingredient or vehicle Infants < 6 months of age (sun avoidance is most appropriate for very young infants) As the sole component of an overall program of photoprotection Individuals wearing sunscreen may stay in the sun much longer and ‘outlast’ the protection of their sunscreen with resultant skin cancer risk. Hence, always recommend a comprehensive sun protective strategy that includes sun avoidance, seeking shade, wearing protective clothing, along with using sunscreens

9. An ideal sunscreen Broad-spectrum coverage Combination of physical & chemical sunscreens Photostability High substantivity Cosmetically elegant Non-irritant Hypoallergenic Noncomedogenic Economical

10. Measuring Sunscreen Efficacy UVB protection offered by sunscreens is measured by the SPF and substantivity UVA Protection Indices- In vivo testing methods: IPD , PPD, and PFA In vitro method- Diffey critical wavelength determination.

11. SPF – SUN PROTECTION FACTOR SPF is a numerical rating system to indicate the degree of protection provided by a sun care product. It is defined 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 . SPF= MED of photoprotected skin/MED of unprotected skin

12. Important factor in photoprotection is not how much is blocked by sunscreen, but how much is prevented from being absorbed into skin. For SPF15, 6.7% is absorbed into skin , whereas for SPF30, 3.3% is absorbed, which is only half the amount. Also , the amount of UVB needed to cause DNA damage that results in skin cancer is less than the amount needed to cause erythema . Moreover, the amount of sunscreen people use is always less than 2 mg/cm2. Therefore, it is more helpful to choose sunscreen with the highest SPF available. Ultraviolet B absorption (as a %) = 100—( 100/SPF). SPF UVB Absorption % 2 50 4 75 8 87.5 15 93.3 20 95 30 96.7 50 98

13. Adherent property or substantivity Ability of a sunscreen to maintain efficacy and withstand adverse conditions such as exposure to water and sweat . The FDA classifies the terms “water-resistant” and “very water-resistant” depending on the substantivity . 1. Water-resistant sunscreens: ability of a sunscreen to retain its photoprotective properties following two 20 minutes intervals (40 minutes total) of moderate activity in water immersion. 2 . Water proof sunscreens or very water-resistant: doubling aquatic activity time to four 20 minutes activity intervals ( 80 min total). The FDA permits products labeled as waterresistant or very water-resistant to be grouped together under the same term “sweat resistant ”

14. F actors affecting substantivity Base and additives: Sunscreen preparations with a polyacrylamide base are highly substantive to the skin and tend to resist washing off after sweating and swimming. 2. Emollients: decreases substantivity . 3. Formulation: The formulation influences not only the substantivity but also the SPF and cosmetic acceptability of the sunscreen . Lotions are non-greasy, spread easily, and are cosmetically more acceptable but their SPF is generally 15 or less, whereas sunscreens with higher SPF are greasier and less acceptable. Oil-free gels are preferable in acne prone and oily skinned individuals but the SPF of such preparations is lower.

15. a. Japanese standard (PPD; in vivo method): UVA dose that induces pigment darkening 2–24 hours after exposure in sunscreen-protected skin UVA dose that induces persistent pigment darkening 2–24 hours after exposure in unprotected skin

16. A ‘ broad-spectrum’ sunscreen is defined as any product that demonstrates an in vitro critical wavelength of 370 nm or greater. The critical wavelength is defined as the wavelength at which 90% of the total area under the absorbance curve resides, with the absorption measures across the UV spectrum ranging from 290 to 400 nm. Diffey critical wavelength

17. IPD( Immediate Pigment Darkening ) describes the immediate gray-brown pigmentation of the skin as caused by the oxidation of preformed melanosomes in the skin. Caused primarily by UVA and short wavelength of VR Begins soon after UVR exposure and lasts upto 2 hours The transient nature of IPD which requires immediate testing makes it a less than ideal measurement tool of UVA protection . • Persistent pigment darkening (PPD) occurs if pigmentation persists more than 2 hours (higher UVA fluencies 8–25 J/cm2). PPD is measured between 2 and 24 hours following irradiation and has the added benefit 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 .

18. The United Kingdom 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 ratio of a product’s UVA absorbance to its UVB absorbance . Products with better UVA absorbance have a higher Boots star rating

19. b. Australian/New Zealand standard (in vitro method ): A 8 mm layer of the product should not transmit more than 10% of radiation of 320–360 nm or 20 mm layer of the product should not transmit more than 1% of radiation of 320–360 nm. c. European Union guidelines : UVA protection factor (PPD method) = 1/3 of SPF and critical wavelength = 370 nm.

20. LABELING

21. PA –protection factor for UVA classified as PA+, PA++, or PA+++ VERY

22. Classification

23. CHEMICAL SUNSCREEN DEF- These contain one or more chemicals, which absorb specific wavelengths (absorption spectrum) of UVR and convert into heat, not allowing them to reach the viable cells of the epidermis . CLASSIFICATION- UVB sunscreens(absorb entire UVB spectrum) and UVA sunscreens (limited absorption spectrum, primarily absorbing shorter wavelengths of UVA (320–360 nm). Hence, it is easier to protect against UVB and short UVA than against longer UVA (360–400 nm). DISADVANTAGE- Less useful in photodermatosis due to poor UVA action

24. 2 nd most potent UVB absorber Weak, high conc. req Thick, oily Because others are lipid soluble and greasy, this is water soluble and less oily M.pot en t UVA2 UVA1 Lower RI, appear less white ECAMSULE

25. Avobenzone is photounstable , it cause degradation of other sunscreen ingredients like octinoxate . Octocrylene plays role in stabilizing avobenzone . Without octocrylene , avobenzone is degraded by 50% upon 1 hour of UV exposure, rendering the sunscreen less effective.

26. Inorganic (Physical) Sunscreens Aka sun blocks formulations containing opaque particulate ingredients such as zinc oxide, titanium dioxide (5–20%), talc, magnesium oxide, kaolin, and ferric chloride. zinc oxide and titanium dioxide are most frequently used . act primarily by reflecting and scattering UV and VR, though some chemicals also exhibit absorptive properties. Barium sulfate and talc attenuate VR and UVR only by scattering. Titaniumdioxide and zinc oxide exhibit a semiconductor optical absorption gap, absorbing most radiation between 290 and 400 nm but scattering most of the radiation of longer wavelengths (VR).

27. Factors affecting effectiveness of inorganic sunscreens Reflective index: Sunscreens with a higher reflective index have better protection but are cosmetically less accepted. Ex-Titanium dioxide has a higher reflective index than zinc oxide and is less cosmetically acceptable. 2. Particle size: Micronized pigment-containing sunscreens offer good protection against UVB induced immuno -modulation . Ex- Microfine zinc oxide protects over a wide range of UVA including UVA1 , while microfine titanium dioxide protects against UVA2. 3 . Dispersion in base. 4 . Film thickness.

28. Advantages chemically inert, safe, and absorb or reflect through the full UV spectrum are suitable for patients with sensitive skin and in very young children Vitiligo on the Sun-exposed parts- use physical sunscreens after psoralen phototherapy. Also protect against VL-aggravated dermatoses such as porphyrias They are not easily washed off when the skin is immersed in water but give limited protection if the sun exposure is extended beyond 2 hours.

29. Disadvantages Poor cosmetic acceptance (gritty consistency & leave a mask-like residue on the skin) Overcomed by- Adding other pigments, such as iron oxide, that simulate flesh tones may partially camouflage this effect Reducing the particle size of chemical to a microsize or ultrafine grade and making it less visible on the skin surface , microsized (‘ nanosized ’). But Changing the form results in their functioning by absorption and not simply blocking UVR, making TiO2 less effective in the UVA range than an opaque physical blocker. Even with this limitation, this ingredient can be classified as a broad-spectrum agent. Using combination sunscreen

30. Sunscreen Vehicles Determine sunscreen efficacy – affect uv absorption of active agents E sthetics Durability Water resistance

31. Emulsions. The most commonly used sunscreens are lotions (thinner, less greasy, large body area) and creams . Oil-in-water and water-in-oil emulsion Since sunscreen ingredients are oil soluble, most products are oil in water emulsions Higher-SPF=more sunscreen oils=more stickiness( heavy, greasy feel ) So-called dry lotions, often labeled ‘sport lotions,’ are an attempt to formulate a less oily product using newer polymeric film formers and less greasy silicone oils . Newer ‘ ultrasheer ’ products further refine these qualities with the use of silica as a major vehicular component.

32. Gels Disadv - E asily removed by swimming or perspiration Tend to more readily cause facial or eye stinging . Adv- F avored by individuals with oily skin or those who are acne prone. Easier to use for individuals with thinning scalp hair or abundant body hair .

33. Nanoparticles in Sunscreen Advantage- No white cast Vehicle is more transparent, less viscous, and blends into the skin more easily. Disadvantage- Because of their diminutive size, Nanoparticles may evade the human body’s natural clearance modalities and immune defenses, so it possesses greater harm.

34. Sprays Adv- convenience of application useful for forehead application to minimize stinging of the eyes, and for scalp areas with thinning hair Disadv - difficult to apply evenly can produce a discontinuous film, resulting in a less effective sunscreen product. The FDA has not approved sprays as a dosage form

35. Sticks Thickened with waxes and petrolatum most lipid-soluble sunscreens can be readily incorporated into sticks. Sticks are helpful for protecting limited areas of the body, such as the lips, nose , or around the eyes. Cosmetics. Adv- Daily protection , superior esthetics, better compliance with their use, commercially available to consumers yearround , Foundation make-up, without UV filters and SPF designation , may provide some protection (generally around SPF,4–5 ) because of its pigment content . By raising the level of pigments (including TiO2), or by adding a chemical sunscreen, a higher SPF can easily be achieved. By virtue of its opacity, foundation make-up also provides the benefit of some UVA protection .

36. Adverse Reactions To Sunscreens Subjective irritation(m/c )—immediate stinging , burning, itching on application, without associated visible erythema . (eye area m/c) Contact urticaria ( Erythema occurring imm . on contact)— immunologic ( IgE mediated)/ nonimmunologic ( toxic or direct mast cell degeneration ) ICD/ACD Photosensitivity ( oxybenzone - m/c/c, Octocrylene & Avobenzone ) Acnegenicity (induce or exacerbate acne)/ Comedogenicity Contact folliculitis - rapid onset of small follicular papules and pustules shortly after product application- reduced by gels and spray Low levels of Vit D

37. Sunlight, specifically UVB at 310 nm, is a major source of the biosynthesis of active vitamin D3. Sunscreen effectively blocks UVB absorption and thereby reduces or shuts down vitamin D synthesis in the skin. Patients may get UVR through noncovered areas to maintain adequate vitamin D levels. For individuals practicing rigorous photoprotection , daily intake of vitamin D through diet or supplements of 600 IU needed. For those 71 years of age and older, 800 IU is recommended.

38. Instructions To Patients Regarding Sun Protection Measures • Sunscreens are most important from 10:00 AM to 4:00 PM ( day light savings time ) when the sun’s rays are strongest . avoid significant sun exposure during these peak hours, by staying in the shade or indoors. • For intermittent, casual daily use, a sun protection factor (SPF) 15 sunscreen is sufficient. For prolonged recreational exposures, an SPF 30 is more desirable, particularly for fair-skinned individuals. • Sunscreen should be applied 15 to 30 minutes before sun exposure to allow sufficient time for the protection to develop , and subsequently reapplied every 2 hours. • Sunscreen should be reapplied after prolonged swimming or vigorous activity leading to sweating . (use water resistant or waterproof ) • Sunscreen needs to be applied liberally. Up to 1 oz(30ml) needed to cover the whole body. Remember to apply to all areas, including the back of the neck, ears,lower lip and areas of the scalp with thin hair. • Clothing ( tightly woven, cotton, yarn, darker clothes)- Check by seeing whether light comes through when held up to visible light. Otherwise sunscreen may be needed under clothing or hats. • A 4-inch wide broad-brimmed hat is required to cover the entire face and neck.

39. Teaspoon rule To achieve application of 2 mg/cm2, the following should be applied: 1 teaspoon of sunscreen to the face/head/neck 1 teaspoon to each upper extremity 2 teaspoons total for the front and back torso 2 teaspoons to each lower extremity. Another approach ( easier and more practica )l is to advise patients to apply sunscreens in two coats, similar to when painting a house. Advantages – ( 1) it is easier to remember (2) any areas that were missed the first time around will likely be covered (3 ) an increased amount is applied 2 2

40. Recommendations for Sunscreen Application (3ml) (6ml)

41. Special Patient Group Instructions 1)Photosensitive Patient Pt. with Photodermatoses , PMLE, taking photosensitizing drugs, or in whom melasma or lentigines darken despite the use of sunscreens, need better UVA protection. Benefit from a higher-SPF product that contains avobenzone , ecamsule , TiO2, or zinc oxide. Available sunscreen agents fail to protect adequately beyond 380 nm, and physical blockers will only protect in the visible spectrum if opaque, and not micronized . For PCT and other porphyria patients sensitive to visible light, only an opaque preparation containing these pigments (as with a make-up) will block this portion of the spectrum .

42. 2) Sensitive Skin A careful history of previous sunscreen Patients should be informed that subjective stinging in or near the eyes should not be interpreted as a sign of true allergy. The patient can be instructed to perform a limited usage test (repeat open application test ) with a previously used or recommended sunscreen product. If true allergy is suspected, consider patch-testing Use chemically inert inorganic particulate materials (TiO2 or zinc oxide ) as the only active ingredients provides a suitable alternative for patients 3)Acne-Prone Patients- Oil-free, alcohol-based gel or a lighter-feeling cosmetic sunscreen moisturizer. Even an oil-free product may feel somewhat oily, as the active sunscreen ingredients are themselves oils. The oil-free claim merely refers to the vehicle. 4)Pregnancy- for prevention of melasma 5)Children- Below 2yrs, prefer Physical sunscreen(broad spectrum, less irritation, minimal skin penetration)

43. Sunless Tanners Self-tanning or sunless tanning products contain dihydroxyacetone (DHA) DHA is a three-carbon sugar that reacts with the amino group of amino acids, peptides, or proteins found in the keratin and epidermis . Melanoidins are formed as a result of the Maillard or ‘browning reaction’ in the stratum corneum DHA provides SPF 3 or 4 protection. The brown color obtained on the skin does absorb the low end of the visible spectrum, with overlap into the long UVA, and may provide some UVA-1 protection. Because the resultant color from these products can last up to several days, patients also need to be reminded that the duration of UV protection is more shortlived than that of the skin color change.

44. Immune Protection Factor IPF is the ability of sunscreen products to prevent UV-induced immunosuppression . IPF is assessed by complex methods such as the ability of a sunscreen to inhibit either the sensitization or elicitation arm of contact or delayed-type hypersensitivity reactions to allergens such as dinitrochlorobenzene and nickel, respectively . IPF is considered to correlate better with the UVA protectiveness of a sunscreen than with its SPF

45. Clothing Indices UPF(UV Protection factor)- measures amt of UVR that can penetrate fabric and reach skin ratio of average effective UV radiation irradiance transmitted and calculated through air to the average effective UV radiation irradiance transmitted and calculated through a fabric I ndicates how much longer a person can stay in the Sun when fabric covers the skin, erythema being the endpoint Grading of UPF: Good protection (UPF: 15–24); Very good protection (UPF: 25–39); Excellent protection (UPF: 40–50+). Fabric SPF is similar to SPF, except that fabric is used to protect the skin while testing instead of a sunscreen .

46. New Sunscreen Technologies SunSpheres SunSpheres are styrene/ acrylate copolymers that do not absorb UV irradiation but enhance the effectiveness of the active sunscreen ingredients. The SunSphere polymer beads are filled with water , which migrates out of the particle, leaving behind tiny air-filled spheres, which have a lower refractive index (1.0) than the dried sunscreen film (1.4–1.5). As a result, scattering of UV radiation occurs , increasing the probability of contact with the active UV filters in the sunscreen . SunSpheres are also available in a powder form and can boost SPF by 50–70%, making it possible to reduce the concentration of active ingredients.

47. Microencapsulation Active sunscreen ingredients are entrapped within a silica shell, as a result of which allergic or irritant reactions to the active ingredient can be minimized, and incompatible sunscreen ingredients can be safely combined without loss of efficacy.

48. Systemic Photoprotection Systemic sunscreens - compounds that have a systemic photoprotective effect EX- β- Carotene Antimalarials ( chloroquine , HCQ, and quinacrine ) O ral psoralens- 8-Methoxypsoralen (8-MOP) and trimethyl psoralen (TMP) Ascorbic acid, α- tocopherols , retinol (i.e., vitamins A, C, and E) Selenium, green tea polyphenols, PABA, antihistamines, aspirin, indomethacin , and corticosteroids