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Photobiology and sunscreen

FULL PHOTOBIOLOGY WITH SUNSCREENS IN DETAIL

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Photobiology and sunscreen

  1. 1. PHOTOBIOLOGY DR. SHILPA SONI.
  2. 2. LIGHT • Speed = 3x10^8 m/sec Travels in straight line
  3. 3. ELECTROMAGNETIC SPECTRUM • Consist of 7 components – Radio waves – Microwaves – Infra-red radiation – Visible light – Ultra-violet waves – X-rays – Gamma rays 105 m 10-14 m Wavelength Rich Men In Vegas Use X-ray Goggles
  4. 4. PROPERTIES OF LIGHT • Wavelength (λ) • Energy of light (J) α 1 λ • Power (W) – rate of flow of energy. (W or J/s)
  5. 5. • Irradiance – rate at which light energy is delivered to a unit area is known as the intensity of light or irradiance. Irradiance = J/s/cm² • Dose of light = it is the total amount of light delivered to the skin & is equal to the product of irradiance & time of exposure. Dose = J/cm²
  6. 6. Fate of Light
  7. 7. SOLAR SPECTRUM
  8. 8. Application of Electromagnetic waves Ultra-Violet (UV) Radiation (10-8 to 10-7) • Sunlight is the main source of UV radiation • Ultraviolet lamps are used in sunbeds for artificial tanning. • Used in hospital for sterilisation - kill bacteria and viruses
  9. 9. Application of Electromagnetic waves Visible Light (10-7) • Only part of the EM spectrum that can be detected by human eye. • Wavelength: 400nm (violet) to 700nm(red) • Laser can be used in industries to weld metals together and in medicine. • Optical fibres in telecommunications
  10. 10. Application of Electromagnetic waves Radio waves (10-1 to 105) • Longest wavelengths • Able to go around obstructions due to their long wavelength • Used in radio broadcasting, telephone transmission, television, radar, navigation system
  11. 11. Application of Electromagnetic waves Microwaves (10-3 to 10-1) • Microwave oven – cause the water molecules in the food to vibrate. The vibration causes friction at a molecular level which will heat up the food. • Satellite communication and television – signals are transmitted through aerial dishes to satellites in the space.
  12. 12. Application of Electromagnetic waves Infra-red Radiation (10-7 to 10-3) • All object emit infra-red radiation • We experience infrared-radiation in the form of heat • Ear thermometer: measure the amount of infra-red radiation that emanates from the eardrum. • Used in remote controls for electronic devices and infra-red motion detectors.
  13. 13. Application of Electromagnetic waves X-Rays (10-13 to 10-8) • used to produce the X-ray images to examine a person’s body or tooth decay • used in X-ray scanners in airports • can penetrate through all materials except lead.
  14. 14. Application of Electromagnetic waves Gamma Rays (10-14 to 10-10) • It can be used to treat cancer by killing cancer cells. • Cause serious damages to living tissues.
  15. 15. PHOTOPROTECTION
  16. 16. Types of sun protection • Natural - Atmosphere • Biological factors - Melanin - Stratum corneum - Chromophores
  17. 17. Types of sun protection • Physical factors - Clothing - Hats - Make up - Window glass
  18. 18. Types of sun protection • Artificial photoprotection • Systemic photoprotection
  19. 19. Types of sun protection Artificial photoprotection - Topical sunscreen - SPF - Substantivity - Types - Organic/chemical - Inorganic/physical - Combination sunscreen
  20. 20. Sunscreens • Organic (chemical) absorbers - UVB absorbers PABA derivatives PABA Cinnamates Cinoxate Salicylates - UVA absorbers Benzophenones oxybenzone dioxybenzone Dibenzoyl methanes avobenzone
  21. 21. Sunscreens • Inorganic/physical/ sunblocks absorbers - Titanium dioxide - Zinc oxide • Others/broad spectrum chemical - Mexoryl SX - Tinosorb M - Tinosorb S
  22. 22. Types of sun protection • Systemic sun protection - Beta – carotene - Anti – malarial drugs - Psoralens
  23. 23. Systemic sun protection • BETA – CAROTENES Mechanism of action - Photo oxidised by UVR and this spares the cell components from being photo damaged. - Free radical scavenger & free radical quencher.
  24. 24. Beta carotene • Uses - Erythropoetic porphyria - PLE - SU • Doses - 30-120µgm in children - 120-300µgm in adults
  25. 25. Antimalarials: Actions in Dermatology • Bind to porphyrins and facilitate their clearance in urine • Solubilization and mobilization of hepatic porphyrins and their clearance • Ability to bind to melanin and antioxidant activity: ?Role in photosensitive disorders • Binds to melanin in retina leading to retinal toxicity
  26. 26. Systemic sunscreen? • Useful for diseases exacerbated by UVB (SCLE > ACLE) as well as those exacerbated or induced by UVA (polymorphous light eruption & its variants & majority of photosensitivity dermatoses) • Blocks effects of exposure on skin as well as other organs esp. in LE • Antioxidant effect & blockage of a cascade of immunologic actions that follow light exposure
  27. 27. Anti - malarials • Uses - PLE - SU - PCT - SLE & DLE • Doses - Chloroquine = 250-500mg/day - Hydroxychloroquine = 200-400mg/day
  28. 28. Anti - malarials • Monitoring - Ophthalmic examination - Visual acuity - Perimetery - Color vision - Ophthalmoscopic avaluation (at every 6 months interval)
  29. 29. Anti - malarials • Toxicity - Reversible corneal deposits - Retinopathy - Optic atrophy - Pigmentary degeneration of macula. (bull’s eye retinopathy) - Arteriolar narrowing
  30. 30. Contraindications • Hypersensitivity (cross reactions) • Pregnancy and lactation • Severe blood dyscrasia • Severe hepatic dysfunction • Retinal & Visual field changes
  31. 31. Systemic sun protection • Psoralenes - 8 MOP - TMP (in conjunction with carefuly controlled exposure to either sunlight (PUVAsol) or an artificial source of UVA (PUVA) can be effective method of increasing skin’s resistance to the damaging effect of UVB component sun light)
  32. 32. Psoralenes • Indications - PLE - SU - AR
  33. 33. Psoralenes • Doses - 8 MOP = 0.6mg/kg - TMP = 0.3mg/kg
  34. 34. Psoralenes • Toxicity - Gastric discomfort - Insomnia - Anxiety - Depression - Photo toxicity - Risk of SCC
  35. 35. THANK YOU

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FULL PHOTOBIOLOGY WITH SUNSCREENS IN DETAIL

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