UV PROTECTION AND EVALUATION OF EFFICACY OF SUNSCREENS 321 already (Figure 6). Investigations carried out by many researchers indicate that UV-induced oxidative stress leads to the development of skin cancer (3) as illustrated in Figures 8 and 9, whereas a certain level of UV exposure on skin prevents or reduces protective mecha- nism in the skin (3). Figure 4. The mechanism involved in wrinkling through alteration of elastic fi bers. Figure 5. Signaling pathway leading to sun burn cells.

JOURNAL OF COSMETIC SCIENCE 322 Hence, it is clear from Figures 8 and 9 that oxidative damage is important for skin carcinogenesis. PHOTOPROTECTIVE AGENTS Various synthetic and natural agents are available in the market for the purpose of photo- protection. Commonly used sunscreens are topical formulations. Nevertheless, various antioxidants, vitamins and minerals also claim to act as systemic photoprotective agents. Topical sunscreens commonly have UV fi lters (UVA or UVB fi lters) and antioxidants as major components. They can act by different mechanisms like refl ecting or scattering and by absorbing UV photons (30). UV fi lters used in sunscreens can be divided into two categories, that is, inorganic and organic sunscreens. The categorization of different types of photoprotective agents is summarized in Figure 10. Many systemic agents with photoprotective effect have fascinated researches, as these are likely to exterminate the veritable problem by shielding the whole body. The dietary fac- tors that claim to act as photoprotective agents are vitamin C, E, A, β-carotene. Many of systemic photoprotectants including steroids, indomethacin, etc., which are antioxidants, are not as potent as sunscreens in protecting the results of hyperpigmentation, for ex- ample, sunburn. Figure 6. Mechanism of UV induced immunosuppression.