department seminar ...uses of dermatology

seminar

1. Sunscreens By Dr.Sankalp Katara Moderator- Dr.Manisha Nijhawan

2. Electromagnetic spectrum

3. UV radiation

4. Factors influencing skin exposure to UVR

5. Normal cutaneous effects of UVR exposure

6. Stratum corneum melanin Ozone Pollutants and clouds Clothing,make up Window glass,hats Topical sunscreens Systemic sunscreens

7. Clothing Protection for UVB>UVA Measured through UPF UPF recommended level >30 Factors affecting UPF of fabric- Construction of fabric-tighter weaves have a higher UPF than looser ones Type of fiber-wool and synthetic fabrics like polyester have a higher UPF than cotton,linen and rayon Color-darker colored fabrics have higher UPF Laundering-shrinkage after washing increases UPF Hydration-wet fabrics have lower UPF Strech-stretching a fabric decreases its UPF Chemical treatment-optical brightening agents increase UPF while bleaching agents decrease it Distance of fabric from skin-more the distance higher the UPF

8. UV protection factor (UPF) = the ratio of average effective UV radiation irradiance transmitted and calculated through air to the average effective UV radiation irradiance transmitted and calculated through fabric (indicates how much longer a person can stay in the sun when fabric covers the skin, erythema being the end-point). Grading of UPF: good protection (UPF 15 to 24) very good protection (UPF 25 to 39) excellent protection (UPF 40 to 50+)

9. History of sunscreens One of the first sunscreens was invented by chemist Franz Greiter in 1938. Greiter's sunscreen was called Gletscher Crème or Glacier Cream and had a SPF of 2. The formula for Glacier Cream was picked up by a company called Piz Buin, named after the place Greiter was sunburned and thus inspired to invent sunscreen. One of the first popular sunscreen products was invented for the US military by Florida airman and pharmacist Benjamin Green in 1944. This came about because of the hazards of sun overexposure to soldiers in the Pacific tropics at the height of World War II.  Water-resistant sunscreens were introduced in 1977. In 1980, Coppertone developed the first UVA/UVB sunscreen.

10. Definition Sunscreen is “an active ingredient that absorbs at least 85% of radiation in the UV range at wavelengths from 290–320 nm (UVB range) and wavelengths from 320–400 nm (UVA range).” -Textbook of ageing skin by Miranda A. Farage

11. An ideal sunscreen In order to ensure optimal patient compliance an ideal sunscreen would be : Broad spectrum Combination of physical and chemical agents Photostable Substantive Cosmetically elegant Non irritant Hypoallergenic Non comedogenic Economical

12. Classification

13. Indications Sunburn Freckling, discoloration Photoaging Skin cancer Phototoxic/ photoallergic reactions Photosensitivity diseases Polymorphous light eruption (290-365 nm) Solar urticaria (290-515 nm) Chronic actinic dermatitis (290 nm-visible) Persistent light reaction (290-400 nm) Lupus erythematosus (290-330 nm) Xeroderma pigmentosum (290-340 nm) Albinism Photoaggravated dermatoses PIH(post procedure

14. How to apply? Sunscreen should be applied properly to all sun exposed areas (in a concentration of 2 mg/cm  2  ), and allowed to dry completely before sun exposure. It should be reapplied every 2 hours, and after swimming, vigorous activity, excessive perspiration, or toweling. "Teaspoon rule":  3 mL (slightly more than half a teaspoon) For each arm For face and neck 6 mL (slightly more than a teaspoon) For each leg For the chest For the back

15. Parameters of sunscreen efficacy 1.Sun protection factor(SPF)-numerical rating system to indicate the degree of protection provided by a sun care product. ratio of the least amount of UV energy required to produce minimal erythema on sunscreen protected skin to the amount of energy required to produce the same erythema on unprotected skin largely a measure of protection against UVB SPF= [Minimum erythema dose(MED)-Lowest dose of UVR required to produce just perceptible erythema at 24 hours.]

16. Grading system for SPF: Low: SPF 2 - 15 Medium: SPF 15 - 30 High: SPF 30 - 50 Highest: SPF >50

17. SPF 15 blocks 93% of UVB rays   SPF 30 blocks 97% of UVB rays   SPF 50 blocks 98% of UVB rays

18. 2.Subsantivity -The ability of a sunscreen to maintain efficacy and withstand adverse conditions such as exposure to water and sweat. On the basis of substantivity, FDA classifies sunscreens as: water resistant- retain their SPF after 40 min. of water exposure water proof or very water resistant-retain their SPF after 80 min. of water exposure

19. Factors affecting the substantivity Base and additives-Sunscreens with a polyacramide base are highly substantive and tend to resist washing off after sweating and swimming. Emollients-They markedly decrease substantivity. Formulation-whether it’s a lotion,cream,gel or spray. Gels are often the most sensitive to water and sweat removal.

20. UVA protection indices A.Japanese standard  (persistent pigment darkening; in vivo method): B. Australian/New Zealand Standard (in vitro method): 8-μm layer of the product should not transmit more than 10% of radiation of 320 to 360 nm OR 20-μm layer of the product should not transmit more than 1% of radiation of 320 to 360 nm

21. C. European Union guidelines: UVA protection factor (persistent pigment darkening method) = 1/3 of SPF AND critical wavelength = 370 nm D. Boots star rating system (used in the United Kingdom):  In vitro  measurement of the ratio of a product's UVA (320-400 nm) absorbance over its UVB (290-320 nm) absorbance is used to calculate its Boots star rating. Products with better UVA absorbance have a higher Boots star rating.

22. Immune protection factor (IPF) : 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 (DNCB) and nickel, respectively. IPF is considered to correlate better with the UVA-protectiveness of a sunscreen than with its SPF.

23. Organic sunscreens Organic UV filters are active ingredients that absorb UV radiation within a particular range of wavelengths, depending on their chemical structure. Once the UV filter absorbs energy, it moves from a low-energy ground state to a high-energy excited state. From this excited state, any of the following three processes may occur, depending on the ability of the filter to process the energy it has absorbed: Photostable filter: This type of filter dissipates its absorbed energy to the environment as heat energy, and returns to the ground state. It is subsequently fully capable of absorbing UV energy again. Photounstable filter: The filter undergoes a change in its chemical structure, or is degraded after absorbing UV energy. It is not capable of absorbing UV energy again. Photoreactive filter: In its excited state, the filter interacts with surrounding molecules, including other ingredients of the sunscreen, oxygen, and skin proteins and lipids. This leads to the production of reactive species, which may have unwanted biological effects.

24. Mechanism of action of organic UV filters Organic UV filter (Chromotaphore) U.V. Absorption Excited state Photostable Photo-unstable Degradation/structural changes Photo reactive Reactive species

25. Organic sunscreens are further divided into UVB and UVA filters: 1.  UVB filters PABA derivatives - Padimate O Cinnamates - Octinoxate , Cinoxate Salicylates - Octisalate , Homosalate , Trolamine salicylate Octocrylene Ensulizole 2.  UVA filters Benzophenones (UVB and UVA2 absorbers) - Oxybenzone, Sulisobenzone , Dioxybenzone Avobenzone or Parsol 1789 (UVA1 absorber) Meradimate (UVA2 absorber)

26. UVB absorbers 1.PABA derivatives- PABA is an effective UVB filter but its use is limited as it is associated with photoallergy and carcinogenesis. Also stains clothes Derivative-Padimate-O-good safety profile but less protective than PABA 2.Cinnamates- Octinoxate is a less potent UVB absorber but most frequently used. Undergoes photodegradation.

27. 3.Salicylates- Exceptionally stable Octisalate and homosalate are weak UVB absorbers so need to be used in higher concentrations. Used to augment other sunscreens and delay their photodegradation. essentially nonsensitizing and water-insoluble, leading to high substantivity. They are also useful as solubilizers of other poorly soluble sunscreen ingredients, such as the benzophenones 4.Others-octocrylene May be used with other UV absorbers to achieve higher SPF values. If added with avobenzone can increase overall satability of the formulation.

28. UVA absorbers 1.Benzophenones- oxybenzone is the most commonly used Absorbs UVB and UVA2 Photolabile Occasionally causes photoallergy and allergic CD

29. 2.Dibenzoyl Methanes- Avobenzone, with an absorption maximum at 355 nm, is the only agent of this class available in the United States. Although these compounds are capable of a high degree of UV absorption, they are unstable. Avobenzone suffers a loss of protective power through photo degradation.

30. Organic sunscreen advantages: • Thinner in consistency, therefore easier to apply • Can offer a consistent coverage against UVB rays, double check that it protects against UVA rays Organic sunscreen disadvantages: • Can irritate skin • Unless stabilized, Avobenzone breaks down quickly  in  UV light •  Must be applied 15-30 minutes prior to sun exposure

31. Inorganic sunscreens Also called sun blocks Formulations containing opaque particulate ingredients like zinc oxide,titanium dioxide(5-20%), talc,magnesium oxide,kaolin and ferric chloride. Zinc oxide and titanium oxide are the most frequently used. Mechanism-They act primarily by reflecting and scattering UV and VR,though some chemicals also exhibit absorptive properties. -Zinc oxide and titanium dioxide absorb most radiation between 290-400 nm but scatter most of VR.

32. Factors affecting the efficacy of inorganic sunscreens Reflective index-Higher reflective index leads to better protection Particle size-Micronized pigment containing sunscreens offer good protection against UVB-induced immune modulation. Dispersion in base Film thickness

33. Reason for whitish appearance Traditional ZnO and TiO 2 clusters are large(> 200nm) Large clusters can scatter light in many different directions Maximum scattering occurs for wavelengths twice as large as the cluster l > 400 nm This is visible light! 36 Source: Original Image

34. Light eventually goes in one of two directions: Back the way it came (back scattering) -Back-scattered light is reflected Forwards in the same general direction it was moving (front scattering) -Front-scattered light is transmitted When reflected light of the visible spectrum reaches our eyes, the sunscreen appears white.

35. Inorganic sunscreen advantages:  • Offers broad spectrum protection (UVA and UVB) • Works immediately upon application • Nonirritating for sensitive skin, such as infants and children, those with rosacea or redness (by deflecting heat), and acne prone skin • Lasts longer in direct UV light • Most are biodegradable and not harmful to marine ecosystems Inorganic sunscreen disadvantages: • Inconvenient for cosmetic purposes as it has a whitish appearance • Can be thick and hard to apply • Must be applied generously to get full coverage

36.  - Ecamsule ( Mexoryl SX), Silatriazole ( Mexoryl XL), Bemotrizinol ( Tinosorb S), Bisoctrizole ( Tinosorb M) Ecamsule is primarily a UVA filter, the patent for which is held by L'Orιal (sunscreens containing ecamsule are exclusive to L'Orιal and its brands). Tinosorb M is the first of a new class of UV filters that combine the properties of both UV conventional filters (organic and inorganic) - it scatters, reflects and absorbs UV light. Apart from Ecamsule, these filters are not yet US FDA approved, but are being used in other countries, such as the European Union and Canada. Newer generation broad spectrum (UVA+UVB) sunscreens

37. Classification and action spectrum of photosensitive skin disease

38. Adverse effects Subjective irritation- stinging, burning, itching Contact urticaria- immunologic, non immunologic Irritant C.D Allergic C.D Photo sensitivity(rare)-could be due to methoxycinnamate and oxybenzone Acnegenicity (induce or exacerbate acne)

39. Debatable Issues 1. Sunscreen use in infants Although not known to be hazardous, the use of sunscreens is not recommended for infants younger than 6 months.  [3] 2. Nanosized particles Nanosized particles range in size from 1-100 nm. Microfine forms of zinc oxide and titanium dioxide have a particle size of 20-50 nm. Nanotechnology makes inorganic sunscreens more cosmetically acceptable (less whitening of skin after application). In recent years, there have been concerns that nanoparticles can induce free radical formation in the presence of UV radiation. However, studies show that these particles remain on the surface of the skin or in the stratum corneum, and are hence safe for human use. 

40. 3. Vitamin D production There have been concerns that widespread use of sunscreens, particularly those with high SPF, may lead to a significant decrease in vitamin D production. However, there is evidence that though sunscreens can significantly reduce the production of vitamin D under very strictly controlled conditions, their normal usage does not generally result in vitamin D insufficiency. In fact, vitamin D and calcium levels have been found to be relatively normal in xeroderma pigmentosum patients, in spite of strict photoprotection.  4. Hormonal effects Some sunscreens (oxybenzone, avobenzone, octinoxate , padimate O) have been tested for their estrogenic/anti-androgenic properties in animal studies. However, the endocrine effects of these agents remain controversial, warranting further human studies.

41. 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.

42. 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.