Sunscreen allergies are becoming more common, especially with ultra high SPF sunscreens. Higher SPFs contain more chemicals and in higher concentrations. However the additional protection benefits of higher SPF sunscreens is limited.
When protecting against ultraviolet radation the difference between SPF 100 and SPF 50 is 1%. For example, SPF 100 blocks 99% of UVB rays, SPF 50 blocks 98 %, and an SPF 30 blocks nearly as much at 96.7%. SPF 30 is generally recommended as is using sunscreens with either titanium oxide or zinc.
Sunscreens work in one of two ways:
Chemical Absorbers: Most sunscreens absorb ultraviolvet (UV) radiation (the energy from the rays of the sun) and turn this energy into a less dangerous form of radiation that causes less damage to the skin. There are sunscreens that absorb different types of UV radiation, such as UVA and UVB. Chemical absorbers include most of the available sunscreens that can be rubbed completely into the skin.
Physical Blockers: These sunscreens reflect the sun’s radiation away from the skin, so that it is not absorbed. Physical blockers include zinc oxide, the brightly colored sunscreens frequently used on the nose and lips of beachgoers.
While contact dermatitis to sunscreens is not as common as allergy to cosmetics, it is not a rare condition. The reaction to sunscreens can occur anywhere the substance is applied on the body. This is called “photo-contact dermatitis” and usually occurs in a sun-exposed pattern on the body.
Many active ingredients are present in sunscreens that cause contact dermatitis. The chemicals in sunscreens most likely to cause sunscreen allergies are PABA (para-aminobenzoic acid), benzophenones, cinnamates, salicylates, dibenzoylmethanes, and octocrylene.