Topical Sunscreens: A Narrative Review for Contact Sensitivity, Potential Allergens, Clinical Evaluation, and...

Topical sunscreens decrease the quantity of ultraviolet (UV) light from the sun reaching the skin by either blocking or scattering it and help protect the skin from dyspigmentation, photoaging, DNA damage, and photocarcinogenesis, especially in photosensitive individuals. The significant role played by visible light and infrared light in skin pigmentation and photoaging has been recognized in recent years. The majority of broad-spectrum sunscreens protect against UV-B (290-320nm) and UV-A (320-400nm) radiation. Allergic reactions to sunscreens were relatively uncommon compared to their widespread use in the last more than four decades. With growing awareness of problems associated with excessive sunlight exposure, their use has increased exponentially, especially that of cosmetics and other personal grooming products containing UV filters. In recent years, sunscreen agents have been commonly identified as causing allergic contact dermatitis and photodermatitis. Thus, allergic contact dermatitis, photo-irritation, photo-allergenicity, and photo-toxicity (acute/subacute effects) are of immediate concern in the assessment of topical sunscreens for their optimal use. Sunscreen chemicals such as p-aminobenzoic acid (PABA) and PABA esters, the cinnamates, benzophenones, oxybenzone, and dibenzoylmethane that absorb UV radiation are common contact sensitizers capable of producing both allergic contact dermatitis and photodermatitis. The excipients in sunscreen formulations by themselves may also cause allergic reactions. Herein, we review potential allergens, clinical evaluation, and management aspects of topical sunscreen contact sensitivity for their optimal use in clinical practice.