Drug-Induced Photoallergy

Facial skin care products and cosmetics

Facial skin care products and cosmetics can both aid or incite facial dermatoses. Properly selected skin care can create an environment for barrier repair aiding in the re-establishment of a healing biofilm and diminution of facial redness; however, skin care products that aggressively remove intercellular lipids or cause irritation must be eliminated before the red face will resolve. Cosmetics are an additive variable either aiding or challenging facial skin health.

Cutaneous photosensitivity diseases induced by exogenous agents

Cutaneous photosensitivity diseases may be idiopathic, produced by endogenous photosensitizers, or associated with exogenous photosensitizers. Those caused by exogenous agents include phototoxicity, photoallergy, and the exacerbation or induction of systemic disorders in which photosensitivity is a prominent clinical manifestation. Phototoxic disorders have a high incidence, whereas photoallergic reactions are much less frequent. The action spectra for most phototoxins and photoallergens lie in the UVA range. Phototoxic and photoallergic reactions can be distinguished on the basis of pathogenesis, clinical characteristics, diagnosis, and management. Drugs capable of causing phototoxic reactions include psoralens, porphyrins, coal tar, antibiotics, and nonsteroidal antiinflammatory agents. Drugs capable of causing photoallergic reactions include topical antimicrobial agents, fragrances, sunscreens, nonsteroidal antiinflammatory agents, plants, and psychiatric medications. Drug-induced systemic diseases in which photosensitivity is a prominent component include drug-induced lupus erythematosus, porphyria, and pellagra.

Ranitidine-induced photosensitivity

We report the case of a 72-year-old male patient who developed a florid photosensitive eruption while on ranitidine therapy. Ultraviolet A sensitivity was detected by irradiation monochromator testing, suggesting drug-induced photosensitivity. Ranitidine was concluded to be the cause of his photosensitivity since the eruption resolved and the phototest abnormalities returned to normal following cessation of therapy. Similar cases have been reported to the Committee on Safety of Medicines but not published.

A predictive mouse ear-swelling model for investigating topical phototoxicity

Predictive models should be used to determine the phototoxic potential of consumer products intended for topical exposure and outdoor use. To determine the potential of a compound to elicit a phototoxic reaction, a mouse ear-swelling model, which uses a xenon arc ultraviolet (UV) solar simulator as the radiation source, was used. The UV solar simulator delivered UV radiation from 290 to 400 nm (UVB + UVA) or from 320 to 400 nm (UVA) when appropriate filters were used. With this model, the phototoxic potential of nine known phototoxins and three negative test materials was successfully demonstrated. Based on the time of onset of the phototoxic response following test material application and irradiation, both immediate (20-30 min) and delayed-type (48-96 hr) phototoxic responses were demonstrated using this model with anthracene and 8-methoxypsoralen, respectively. The optimal time for irradiation after application of 8-methoxypsoralen to the ears was 30-60 min. Irradiation of ears immediately after treatment with 8-methoxypsoralen or 6 hr after application resulted in little or no phototoxic response. The phototoxic response to 8-methoxypsoralen was dependent upon the UVA dose and, when tested at a constant UVA dose, the response was concentration dependent. To obtain an optimal phototoxic response to 7-methoxycoumarin, both UVB and UVA radiation were required. These results show that the mouse ear-swelling model, which is quantifiable and more objective than models based on subjective evaluation of skin changes, is an excellent model for investigative and predictive phototoxicity testing.