Topical sunscreens have been shown to prevent and even repair damage caused by exposure to UV radiation in animal models. In humans, there is evidence that these products can prevent the acute effects of solar radiation and reduce the incidence of some skin cancers, such as squamous cell carcinoma. Studies have shown that the daily use of a broad-spectrum sunscreen can significantly reduce skin damage caused by UV radiation.
The ideal sunscreen should protect the skin against both UVB and UVA radiation (broad spectrum), scavenge free radicals, and contain enzymes or other active ingredients that will stimulate DNA repair systems. Obviously, these products must also be safe, stable and cosmetically acceptable.
Topical sunscreens are based on ingredients that, by one means or another, prevent UV radiation from reaching skin cells. Rather than focusing on filtering or blocking radiation, the chief innovations in recent years have sought to prevent or counteract the undesirable effects of solar radiation on skin cells through the use of antioxidants and agents such as those that favor the repair of damaged DNA. Sun Protection Factor (SPF)
SPF refers to the ability of a sunscreen to block ultraviolet B (UVB) rays, which cause sunburns, but not UVA rays, which are more closely linked to deeper skin damage. Both UVA and UVB contribute to the risk of skin cancer. It is a measure of the time it would take an individual to burn in the sun if they were not wearing sunscreen vs. the time it would take with sunscreen on.
An SPF 15 product blocks about 94% of UVB rays, an SPF 30 product blocks 97% of UVB rays, and an SPF 45 product blocks about 98% of rays. Sunscreens with higher SPF ratings block slightly more UVB rays, but none offer 100% protection.
In a recent review of sunscreens regulations, the Food and Drug Administration (FDA) proposed a regulation that would require sunscreen products that have SPF values higher than 50 to be labeled as SPF 50+. FDA does not have adequate data demonstrating that products with SPF values higher than 50 provide additional protection compared to products with SPF values of 50.
The American Academy of Dermatology recommends everyone use daily a sunscreen that offers the following: 1. Broad-spectrum protection (protects against UVA and UVB rays) 2. Sun Protection Factor (SPF) 30 or greater 3. Water resistance