We start by noting that allergic contact photoezcemas are uncommon,1 and allergic contact photoezcemas caused by components of sunscreens are also rare.2 A study by the North American Contact Dermatitis Group found a rate of positive reactions of 0.9% to sunscreen components among 23 000 patients who underwent skin patch and photopatch testing because of suspicion of delayed contact hypersensitivity.3

Although oxybenzone (benzophenone-3 according to the International Nomenclature of Cosmetic Ingredients) has been listed for more than 20 years among products that absorb ultraviolet radiation and that are allergenic or photoallergenic, reactions to this compound were uncommon.4

In recent years, however, the frequency of oxybenzone reactions has increased to the point that it is now the main allergen or photoallergen in sunscreens,3 and it was named allergen of the year in 2014 by the North American Contact Dermatitis Group.5 The frequent cross-reactions between benzophenones and other common photoallergens such as ketoprofen, fenofibrate, and octocrylene are also cause for much concern.6

Little has been published on allergies or photoallergies to oxybenzone in Spain.7 However, in cases detected by the Spanish Photobiology Group, sunscreens were the second cause of allergic contact photosensitivity (10 of 103 positive results) after nonsteroidal antiinflammatory drugs. Of all sunscreen components, benzophenone-3 was the one responsible for most positive results in 2006 (5 of 103 positive results).8

In this issue of the journal, Russo et al.9 provide new information that points to oxybenzone as the main cause of allergic contact eczemas and photoeczemas in La Plata, Argentina.

Benzophenone-3 is, in contrast, an uncommon cause of contact urticaria induced by cosmetic components.10

In addition to adverse cutaneous effects, the presence of these products in urine and breast milk, contamination of fresh water, and transformation to other even more toxic products in chlorinated water and possible hormonal disruption are of great concern to toxicologists.11

Sunscreens are an essential part of the prevention and treatment of skin diseases, but like other interventions, they are not devoid of adverse effects.