Hydrochlorothiazide, also known as Microzide in the United States and Apo-Hydro and Novo-Hydrazide in Canada, is a medication used to treat high blood pressure. Considered a diuretic, hydrochlorothiazide lowers blood pressure and eliminates excess salt and water in your body through the kidneys. It boosts your production of urine. Some people who take hydroclorothiazide have a photosensitivity reaction triggered by exposure to ultraviolet light, or sunlight. One of the symptoms of this reaction is itchy skin.
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Some 95 percent of photosensitive reactions due to hydroclorothiazide are considered phototoxic, Dr. Miriam Lindrooth explains. If your skin turns red, swells and burns after minutes or hours of exposure to sunlight, you are experiencing a phototoxic reaction. The reaction mirrors sunburn and is localized to only the skin that was exposed to ultraviolet light. If you have a severe reaction, your skin may break into hives and blister. If you stop taking hydroclorothiazide, these symptoms will typically vanish within two to seven days.
If you have a photoallergic reaction to the sun, it will occur 24 to 72 hours after exposure to ultraviolet light. The reaction may spread to areas of body that were not exposed. The symptoms resemble eczema. Your skin will become very itchy. The cause of a photoallergic reaction stems from the antibodies that your body produces when you take hydroclorothiazide, which makes your skin ultrasensitive to the sun. If you stop taking hydroclorothiazide, the symptoms will disappear.
Apply topical corticosteroids, such as hydrocortisone cream, to the affected areas of your skin. You can also use soothing lotions and cool compresses to relieve any inflammation or swelling. Oral antihistamines will ease the itching. If you’re unable to stop taking hydroclorothiazide because it will put your health at risk, check with your doctor to see if you can switch to evening doses.
Avoid direct sunlight, particularly during the midday hours when the sun is the strongest. Wear a hat and sunglasses and other protective garb to shield your skin. Apply sunscreen with an SPF of 15 or more and use protective lip balm. Avoid using tanning beds or sun lamps.