Sunlight lifts moods, enables vitamin D production, and warms the body and soul. It can also cause a range of ill effects including sunburn, heat exhaustion, and heat stroke—particularly when combined with medications that change how the body responds to sunlight and heat. As the high temperatures of summer linger, consider alerting customers to heat- and sun-related side effects of common OTC and prescription medications.

For some drugs, encouraging the purchase of a good sunscreen may be all that’s needed, but avoiding a burn right after sun exposure is just part of the challenge. Drugs that increase sun sensitivity can cause phototoxicity, usually indicated by skin irritation or much worse than expected sunburn following sun exposure. Topical drugs in particular can also trigger photodermatitis or photoallergy, which may not appear for a few days. Common signs include itching, rash, redness, and swelling of sun-exposed skin. In individuals with darker skin tones, both kinds of reaction may cause hyperpigmentation.

Several broad classes of drugs increase sun sensitivity. People starting a new antibiotic should limit sun exposure when taking tetracyclines, fluoroquinolones, and sulfonamides. Antifungals, calcium channel blockers, diuretics, oral contraceptives, sulfonylurea drugs for diabetes, statins, and tricyclic antidepressants also increase the chance of getting a nasty burn, according to the FDA.

Popular OTC medications can also cause severe sunburn. Ibuprofen, naproxen, and many antihistamines increase sun sensitivity, as can supplements, particularly St. John’s wort. Customers using retin A–based acne treatments are likely aware that they increase photosensitivity, but they (and others) may not realize that the alpha-hydroxy acids in many cosmetics do as well.

Other drugs increase the risk of heat-related illness on the continuum from heat exhaustion to heat stroke. While young children and elderly adults are most susceptible, anyone can be affected and should take steps to reduce their risk. Early signs include headache, dizziness, nausea and vomiting, and muscle cramping and can progress to weakness, high fever, difficulty breathing, lack of sweating, rapid pulse, confusion, collapse, and seizures. Heat stroke is a potentially fatal medical emergency.

Many common medications can impair the body’s ability to respond appropriately to heat, making heat-related illnesses more likely. Migraine and allergy medications and other vasoconstrictors, as well as tricyclic antidepressants, phenothiazines, and anticholinergics, all reduce sweating, a key tool in temperature regulation. Beta-blockers also impair the body’s ability to offload heat by slowing blood flow to the skin, while stimulants used to treat attention-deficit/hyperactivity disorder and narcolepsy raise base body temperature. Diuretics increase the risk of dehydration, often a factor in heat exhaustion.

Other medications that increase the risk of heat-related illnesses include benzodiazepines, calcium channel blockers, laxatives, neuroleptics, and thyroid agonists.

In addition to wearing sunscreen, individuals taking these medications should be urged to avoid staying outdoors on hot days and to drink plenty of fluids.

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