Natural Sunscreen Agents: A Review

The exposure of skin to ultraviolet B (UVB) radiation has a destructive effect on keratinocytes by causing DNA damage that can subsequently lead to malignant transformation. Cellular defense mechanisms against this injury begin with the immediate UVB-induced death of damaged cells. In less severely affected cells, cell-cycle progression can be blocked and DNA damage can be repaired through nucleotide excision repair (NER). If repair is successful and cells have not suffered irreversible damage, they will survive. In the absence of appropriate repair, keratinocytes undergo apoptosis, producing characteristic „sunburn cells‟. Sunscreen is defined as substance that protects the skin from excessive exposure to the ultraviolet radiation of the sun. Sunscreen use is often proposed for sun protection because of their ability to block UV-induced sunburns (the sun protection factor –SPF). It helps to prevent sunburn and reduce the harmful effects of the sun such as premature skin aging and skin cancer. They are routinely tested in humans and can be assigned a sun protection factor (SPF) which reflects their ability to prevent sunburn. Sunscreens are found in cream, lotion, gel, stick, spray, and lip balm type‟s forms. They are for external use only. An attempt has been made to review natural sunscreen agents.