Are all sunscreens created equal especially if they bear the same Sun Protection Factor (SPF) number?
Dr. Sommerville: Expressed as a ratio of the Minimal Erythema Dose (MED) for sunscreen-protected skin to the MED for unprotected skin translating to the length of time a sunscreen prevents skin reddening from UVB compared to how long it takes to redden without a sunscreen, the SPF measures protection only from UVB radiation. SPF rating gives no indication of user’s protection against UVA radiation which is also implicated in photocarcinogenesis (ultraviolet-induced skin cancer formation) trough suppression of the immune system. UVA rays are also responsible for up to 80% of skin aging. Some of the manifestations of skin aging include hyperpigmentation, leathery appearance, wrinkles, blotchiness, tactile roughness and telangiectasiae (broken capillaries). Since there is currently no well-established scale for measuring the protection against the UVA, one must consider the sunscreen ingredients, some of which offer relatively good level of protection against UVA. Another frequent misconc
Dr. Sommerville: Expressed as a ratio of the Minimal Erythema Dose (MED) for sunscreen-protected skin to the MED for unprotected skin translating to the length of time a sunscreen prevents skin reddening from UVB compared to how long it takes to redden without a sunscreen, the SPF measures protection only from UVB radiation. SPF rating gives no indication of user’s protection against UVA radiation which is also implicated in photocarcinogenesis (ultraviolet-induced skin cancer formation) trough suppression of the immune system. UVA rays are also responsible for up to 80% of skin aging. Some of the manifestations of skin aging include hyperpigmentation, leathery appearance, wrinkles, blotchiness, tactile roughness and telangiectasias (broken capillaries). Since there is currently no well-established scale for measuring the protection against the UVA, one must consider the sunscreen ingredients, some of which offer relatively good level of protection against UVA. Another frequent misconc
