Medicines and the Sun May Not Mix
by Linda R. Bernstein, Pharm.D.
Vacations and the sun often go hand in hand, so it is good to keep in mind that besides sunburn, you may be at risk of a photosensitivity reaction – an abnormal and sometimes severe skin reaction to sunlight, sometimes triggered by oral or topical medicines, whether prescription or nonprescription products. Reactions due to medicines are of two types, phototoxicity (the most common), and photoallergy (uncommon). They can occur at any age.
Phototoxicity
This reaction looks like an exaggerated sunburn, with redness, swelling and sometimes blisters in sun-exposed skin only. The skin usually peels within a few days. The reaction occurs upon the first use of a drug, within minutes to hours after sun exposure. The more drug taken and the more sun exposure, the greater the phototoxic reaction. Once the medication is stopped, the skin reaction will go away. Most phototoxic reactions occur after medicines that are taken internally.
Photoallergy
This reaction involves not only the drug and sunlight, but the person’s immune system as well. It occurs in only a small portion of persons previously exposed to the medicine. Unlike phototoxic reactions, photoallergy is not related to the amount of medicine you take, even a small amount can trigger the reaction. The onset of the rash is more delayed (twenty-four to forty-eight hours after sun exposure) and is slower to clear, even after the drug has been stopped. The rash generally occurs on areas exposed to the sun, such as the face, hands and neck, but in severe cases it may spread. The rash may look like eczema, hives, hardened patches, blisters or small broken blood vessels. Photoallergic reactions can be caused by topical (medication applied to the skin) or oral administration of the drug. These reactions occur more commonly in men.
Treatment
For an acute photosensitivity reaction, avoid further exposure to the sun and stop taking the offending medication, if possible. Check with your healthcare provider if you have to stop taking your medicine. They may be able to prescribe another product without the sun-sensitizing effect. Cool wet dressings, soothing lotions, nonprescription hydrocortisone cream and oral anti-itch (antihistamine) medications or aspirin may be used to relieve symptoms. Sometimes prescription topical steroids are required to reduce inflammation. Consult your physician or pharmacist for recommendations and make sure that the products they choose do not contain photosensitizing ingredients. Note: Some nonprescription antihistamines are known to contain photosensitizers as diphenhydramine.
Prevention
The best prevention is to stay out of the sun, or at least wear protective clothing – wide-brimmed hats, long sleeves and pants made of lightweight but tightly woven fabrics.
Sunscreens may have limited effectiveness because they may not protect against the entire range of UV radiation causing the reaction. Broad-spectrum sunscreens with coverage in the UV-A and UV-B ranges are recommended. Some sunscreens contain ingredients that may themselves be sun-sensitizing, such as PABA.
Photosensitizers
A number of medicines are known to be photosensitizers, and can trigger a photosensitivity reaction. If you take a medicine and plan to spend time in the sun, consult your physician or pharmacist to make sure that you are not placing yourself at risk.
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Other resources about photosensitivity:
Drug-Induced Photosensitivity
Updated: Sep 18, 2020, Medscape
https://emedicine.medscape.com/article/1049648-overview
Photosensitivity Reactions
Updated: Dec 2019, Merck Manual Consumer Version
