True Photoallergy to Sunscreens is Rare Despite Popular Belief

Abstract and Introduction

Abstract

Background: Rising use of sunscreen products has led to increased reporting of adverse reactions to sunscreens.
Objective: To investigate possible photoallergic reactions in patients who identified themselves as "being allergic" to sunscreens.
Methods: Patients filled out questionnaires about types of sunscreens they used and timing of their "allergic" reactions. Next, they consented to be photopatch-tested with active sunscreen ingredients, including the new sunscreen Anthelios SX (containing Mexoryl SX) and the new ultraviolet filters Tinosorb M and Tinosorb S. Standard allergen patch testing was also done.
Results: Twenty-seven patients self-reported "sunscreen allergy." Photopatch testing is difficult for patients; hence, only 11 agreed to proceed with the testing. Eight patients had negative patch testing results. One patient reacted to benzophenone-2. Another had a prior reaction to titanium dioxide and titanium oxalate but did not react to the silicone-coated titanium in our study. Yet another patient had relevant photopatch reactions to benzophenone-3 and ethylhexyl dimethyl para-aminobenzoic acid (PABA). None reacted to the Tinosorbs or Anthelios SX. Few positive reactions to the standard allergens were not relevant.
Conclusion: Although small, this study parallels prior studies in concluding that true delayed type IV hypersensitivity (allergic contact dermatitis and photoallergy) to sunscreens is more infrequent than patients tend to believe.

Introduction

Increased Public Awareness of the harmful effects of ultraviolet (UV) light exposure has greatly increased the use of sunscreen products in developed countries.^[1] Sunscreen and sunblock chemicals may be found in a diverse variety of skin care and cosmetic products. As a result of increased exposure, reports of adverse effects to sunscreen products have increased.^[2,3] Up to 19% of patients report experiencing an adverse event due to sunscreen-containing products.^[4] Adverse effects from sunscreen products may include urticaria, allergic and irritant contact dermatitis, and phototoxic and photoallergic reactions.^[2] Numerous nomenclatures exist for active sunscreen ingredients. In most countries, the International Nomenclature Cosmetic Ingredient (INCI) names are used. In the United States, there are standardized Food and Drug Administration (FDA) names for sunscreen chemicals. Sunscreen manufacturers are not required to list ingredients by their FDA-standardized names; thus, synonyms are commonly used for various active sunscreen chemicals. This article will refer to sunscreen chemicals by their INCI names; synonyms are provided in Table 1.

Sunscreen products contain active chemicals as well as inactive ingredients, any of which may be problematic (Table 2^[1,3–62]). Past studies revealed that inactive ingredients (such as fragrance, preservatives, formaldehyde releasers, antimicrobial agents, and lanolin) were among the most common culprits in allergic and photoallergic reactions caused by cosmetic products including sunscreens. ^{[4,31,36,52,60]} Since the late 1980s, however, the active chemical sunscreen ingredients have been implicated as increasingly important causes of allergic and (particularly) photoallergic contact dermatitis.^[3,42,60]

The most commonly reported allergen among the active sunscreen chemicals in the 1960s was paraaminobenzoic acid (PABA), whose sensitizing potential created enough concern to prompt its virtual disappearance from the US sunscreen market.^[2] In recent years, most sunscreen products have been advertised as "PABA free."^[63] In the United Kingdom, however, PABA continued to be marketed until 2007 and is still advertised for sale through the Internet.^[8] The next most commonly reported allergenic sunscreen chemical was a derivative of PABA, ethylhexyl dimethyl PABA, for which there were comparatively fewer reports of sensitization or photocontact sensitization.^[64] By the late 1980s, the most commonly reported allergens among the active sunscreen ingredients were the benzophenones; specifically, benzophenone-3 remains the leading cause of allergic and photoallergic reactions to active sunscreen chemicals.^[2,63] The pattern of allergy to chemicals evolves with time; thus, a study of allergic contact dermatitis from both new and traditional sunscreens is timely and relevant.

Active sunscreen chemicals are cited in the literature as the most common photoallergens; however, the true incidence of photoallergic contact dermatitis reactions to sunscreens in the general population remains unknown.^{[3,28,32,33,42,65]} The most common active chemical agents that induce a photoallergic response are benzophenone-3, benzophenone-4, ethylhexyl dimethyl PABA, and the dibenzoylmethanes.^[21] As new sunscreen chemicals enter the market, new incidents of allergic contact dermatitis from these agents are reported, and more are expected. The newest sunscreen chemical on the US market is terephthalylidene dicamphor sulfonic acid (Mexoryl SX, L'Oréal, Clark, NJ), which is an ingredient in Anthelios SX (L'Oréal). The product versions of drometrizole trisiloxane (Mexoryl XL, L'Oréal), methylene-bis-benzotriazolyl tetramethylbutylphenol (Tinosorb M, Ciba Specialty Chemicals Co., Tarrytown, NY), and bisethylhexyloxyphenol methoxy-phenyl triazine (Tinosorb S, Ciba Specialty Chemicals Co.) are not yet approved by the FDA but have been used for many years in Europe and more recently in Canada. A case of allergic contact dermatitis from methylene-bis-benzotriazolyl tetramethylbutylphenol (Tinosorb M) already has been reported in Spain.^[11] Furthermore, an Italian multicenter study of 1,082 patients with histories and clinical features suggestive of photoallergic contact dermatitis noted five positive photopatchtest reactions to Anthelios XL (L'Oreal).^[10] Those reactions were attributed to the active sunscreen chemical Mexoryl XL. Only two of five patients were retested with pure Mexoryl XL, and their reactions were confirmed as photoallergic reactions.

The objective of this study was to profile the allergic and photoallergic reactions to traditional and newer sunscreen chemicals in a series of patients who reported a subjective adverse reaction to at least one sunscreen product. We hypothesized that patients who identify themselves as "allergic to sunscreens" may not have relevant photoallergy or allergic contact dermatitis.

Dermatitis. 2010;21(4):185-198. © 2010  American Contact Dermatitis Society