Vincent St Aubyn Crump, FRCP (UK), FRACP
We all encourage photoprotection, in order to reduce the growing prevalence of actinic keratoses, solar elastosis, and squamous cell carcinoma. With the increased use of sunscreens it is not surprising that there has been an increase in reports of adverse reactions to sunscreens.
Sunscreens function best to prevent sunburn from UV-B radiation. They provide more limited protection from UV-A radiation. Sun avoidance remains the best form of UV protection. Sunscreens are divided into chemical absorbers and physical blockers on the basis of their mechanism of action.
Classification of some of the sunscreens currently used:
Adverse reactions to sunscreen includes:
- Contact dermatitis (reaction to sunscreen independent of UV)
- Reaction to sunscreen requiring UV exposure after application of sunscreen
- Photoallergic reactions
- Phototoxic reactions
Ingredients in sunscreen causing adverse reactions include:
- Active chemical absorbing the UV
- Preservatives especially Quaternium 15
Prevalence of Contact dermatitis to sunscreen agents
This prevalence is not known in the general population, but in a patch test clinic the prevalence of allergy to the active sunscreen ingredient is probably less than 1%.
The prevalence of sunscreen sensitization in individuals referred for evaluation of photosensitivity is much higher. In a photopatch test (application of chemicals to the back for 48 hours and then irradiate the skin with UVA light after removal of the patch with the chemicals) clinic in France 15.4% of positive reactions were related to sunscreens, and 72% were deemed relevant.
Fischer and Bergstrom (1) found that only 5% of pharmaceutical customers complaining of adverse reactions from sunscreens were allergic to active sunscreen ingredients, with most other allergies detected to fragrances like Balsam of Peru
It is important to realise that contact allergy also exists in very young children. When 85 healthy asymptomatic children (Denver, CO area) ages 6 months to 5 years were patch tested with the 24 panel allergen T.R.U.E. TEST, 20 (24.5%) reacted to one or more allergens (2)
Risk Factors for Sunscreen Allergy
- Pre-existing photodermatoses
- Outdoor occupation
Clinical Features of sunscreen allergy
- Eczematous reaction in the sun-exposed areas, such as the “V” of the anterior neck, the backs of the hands, the forearms.
- Typically, the upper eyelids, upper lip, and area under the chin and behind the ears are spared.
- Any skin area that receives sufficient light and is exposed to the photosensitizing.
A case series report in the Australasian Journal of Dermatology (3) reported on their experience with sunscreen allergy between 1992 and 1999 and also review the international literature on sunscreen allergy. There were a total of 21 allergic reactions to sunscreen chemicals observed in 19 patients over the 8 years. There were:
- 9 positive photopatch reactions to oxybenzone,
- 8 to butyl methoxy dibenzoylmethane,
- 3 to methoxycinnamate and
- 1 to benzophenone.
- No positive reactions were observed to para aminobenzoic acid.
- Six patients also had positive patch tests to components of the sunscreen base.
In their experience, sunscreen chemicals are the most common cause of photoallergic contact dermatitis.
In another study reporting on 7 years experiencing of photopatch testing with sunscreen allergens in Sweden (4), of 355 patients with suspected photosensitivity tested 7.9% had an allergic reaction, and 80% of these were of photocontact origin. This is an important point, since doing patch tests only (without photesting) will miss the majority of cases of sunscreen allergy. The allergens were:
- Benzophenone-3 (Eusolex 4360) was the most common allergen -16 reactions
- 15 photocontact allergic reaction
- 1 allergic contact reaction
- isopropyl dibenzoylmethane (Eusolex 8020) – 12 reactions
- 8 photocontact
- 4 contact
- butyl methoxydibenzoylmethane (Parsol 1789 – 6 reactions
- 6 photocontact reactions
- phenylbenzimidazole sulfonic acid (Eusolex 232) – 2 reactions
In that study, 1 case of contact urticaria from benzophenone-3 was accidentally found, this suggests that Immediate-type testing for urticaria is useful.
Para-aminobenzoic acid (PABA) was one of the first chemical sunscreens to be widely available. Several problems limited its use:
- it was associated with a number of adverse reactions. Sensitization to PABA was reported as early as 1974
- it stained clothing, and
- it required an alcoholic vehicle, and
- patients often report a transient stinging or burning sensation after application of PABA-containing products. This condition is more common than true allergy and may lead patients to falsely believe thy are allergic to this chemical
Because of problems with PABA formulations, manufacturers emphasized the PABA-free claim, and several sunscreens are marketed as “hypoallergenic” because they are PABA-free.
Ester derivatives of PABA, mainly padimate O or octyl dimethyl PABA, became more popular, with greater compatibility in a variety of cosmetic vehicles and a lower potential for staining and adverse reactions and now both PABA and padimate O are less frequently used. Padimate O is the most potent UV-B absorber. The decline in its use, along with the demand for higher SPF products, has led to the incorporation of multiple active ingredients into a single product to achieve the desired SPF, replacing single PABA esters
Benzophenones were first used in sunscreen products in the 1950s, and the first description of a contact reaction to benzophenones in sunscreen products was published in 1972 (5). This chemical is probably one of the most common causes of photocontact allergy. In addition to causing contact and photocontact delayed-type hypersensitivity reactions, benzophenones has been reported to cause immediate-type hypersensitivity): photocontact urticaria (hives), contact urticaria, and anaphylaxis. For patch testing, a 10% oxybenzone concentration in petrolatum is used, and generally serves as a marker to benzophenones.
Dibenzoylmethanes are UV absorbing chemicals widely used in continental Europe. Phototocontact allergy has been reported with 4-tert-butyl-4-methoxy dibenzoylmethane (Parasol 1789). The other sensitizer isopropyl dibenzoylmethane (Eusolex 8020) has been withdrawn.
Cinnamates are group of chemicals used in flavourings, fragrances, and less frequently sunscreens. In sunscreens they are often combined with benzophenones. They are often used in sunscreens marketed as “waterproof’.
Contact urticaria from cinnamates used in other skin care product have been reported, but not to sunscreens containing cinnamates.
Salicylates were first used in cosmetics as Benzyl salicylates. Currently octyl salicylate is the major salicylate component of sunscreen. Allergic contact dermatitis from salicylates have been reported only rarely (6)
(1) Fischer & Berystoim K. Evaluation of customers' complaints about sunscreen cosmetics sold by the Swedish pharmaceutical company Contact Dermatitis 1991:25:319-322.
(2) Bruckner et al. Does Sensitization to Contact Allergens Begin in Infancy? Pediatrics 2000;105:1.e3.
(3) Cook, Natasha; Freeman, Susanne Report of 19 cases of photoallergic contact dermatitis to sunscreens seen at the Skin and Cancer Foundation. Australasian Journal of Dermatology. 42(4):257-259, November 2001.
(4) Berne B, Ross AM. 7 years experiencing of photopatch testing with sunscreen allergens in Sweden Contact Dermatitis. 1998; 38(2):61-4
(5) Ramsay DL, Cohen HJ, et al. Allergic reaction to benziphenones. Simultaneous occurrence of urticarial and contact sensitivities. Arch Dermatol 1972; 105:906-8
(6) Dromgoole SH, et al. Sunscreening agent intolerance: contact and photocontact sensitization and contact urticaria. J Am Acad Dermatol 1990; 22:1068-78