Medicines that make your skin more sensitive to the sun

Which common medicines can cause sun reactions, what the 2 reaction types look like, what is known about skin cancer risk, and what to ask your prescriber.

Some medicines absorb ultraviolet (UV) light once they reach the skin. The energy they capture gets passed to nearby cells, and a short walk or a drive can end in a burn or a rash. Doctors call this drug-induced photosensitivity.

The 2 kinds of reaction

Phototoxic reactions are the more common kind. The drug in the skin absorbs UV and releases reactive oxygen molecules that injure cells directly. The result looks like an exaggerated sunburn on exposed areas: the face, the V of the neck, the forearms, the backs of the hands. It can start within minutes to hours of sun exposure, and it can happen to anyone who has enough of the drug on board and enough light.

Photoallergic reactions involve the immune system. UV changes the drug so that the body treats it as foreign. An itchy, eczema-like rash appears 24 to 72 hours after exposure and can spread to skin that was covered. This type is less common and only affects people who have become sensitized. Some products applied to the skin can cause it too, including certain fragrances and a few sunscreen ingredients.

Medicines most often involved

The Food and Drug Administration (FDA) and DermNet both keep lists. Most people who take these medicines never have a reaction, and the risk varies a lot from drug to drug within a group.

• Antibiotics: doxycycline and other tetracyclines, fluoroquinolones such as ciprofloxacin and levofloxacin, and sulfonamides
• Diuretics (water pills): hydrochlorothiazide, chlorthalidone, furosemide
• Nonsteroidal anti-inflammatory drugs (NSAIDs): naproxen, piroxicam, ketoprofen, ibuprofen
• Heart medicines: amiodarone, quinidine, diltiazem
• Retinoids: isotretinoin and acitretin by mouth, and retinoid creams
• Antifungals: voriconazole, griseofulvin
• Cancer drugs: BRAF inhibitors such as vemurafenib, and fluorouracil cream
• Others: phenothiazines such as chlorpromazine, sulfonylurea diabetes pills, psoralens, and the herbal supplement St John's wort

Doxycycline deserves a mention because so many teenagers and travelers take it, for acne and for malaria prevention, often in sunny places. Amiodarone stays in the body for a long time, and its sun sensitivity can last well after the last dose.

Hydrochlorothiazide and skin cancer

Hydrochlorothiazide is one of the most widely used blood pressure medicines in the world. A nationwide Danish case-control study (Pedersen and colleagues, Journal of the American Academy of Dermatology, 2018) compared people diagnosed with basal cell or squamous cell carcinoma between 2004 and 2012 with matched people without skin cancer. People with a high lifetime total of the drug, 50,000 mg or more, had about 4 times the odds of squamous cell carcinoma and a smaller increase, about 30%, for basal cell carcinoma. Risk rose as the total dose rose. Other blood pressure drugs showed no such link.

The study had no information on how much sun each person got, so it shows an association and cannot prove cause. The FDA then ran its own analysis in the Sentinel System and, in August 2020, added nonmelanoma skin cancer to the hydrochlorothiazide label. The agency found the increase was mostly in squamous cell carcinoma and mostly in White patients who had taken large total doses.

The added risk for one person is small. The FDA estimated about 1 extra case of squamous cell carcinoma per 16,000 patients per year, and about 1 extra case per 6,700 per year among White patients with a total dose of 50,000 mg or more. The agency stated that patients should keep taking hydrochlorothiazide unless their own clinician advises otherwise, because uncontrolled blood pressure leads to heart attack and stroke. The label now advises sun protection and regular skin cancer screening.

Voriconazole in transplant patients

Voriconazole treats and prevents serious fungal infections, and lung transplant recipients sometimes take it for months. Transplant patients already have a high rate of squamous cell carcinoma because of their immune-suppressing drugs. Voriconazole appears to add to that. In a Kaiser Permanente study of 3,308 organ transplant recipients (Dusendang and colleagues, Journal of the American Academy of Dermatology, 2022), each month of voriconazole use among lung recipients was linked to a 14% increase in the rate of squamous cell carcinoma of the skin.

Transplant teams weigh this against the danger of a fungal infection, which can be fatal. Many centers limit how long the drug is used, switch to another antifungal when they can, and arrange regular dermatology visits.

Practical steps

Please do not stop or skip a prescribed medicine because of what you read here. Stopping a blood pressure drug, a heart rhythm drug, or an antifungal can be dangerous. Bring the question to the person who prescribed it, or to your pharmacist. Useful things to ask about:

• Whether this medicine makes skin sensitive to the sun, and for how long after the last dose
• Whether taking it in the evening would help
• Whether another medicine would work as well, if you have had skin cancer or a lot of sun damage
• How often to have a skin exam while you take it

While you are on one of these medicines, the FDA's advice is simple: seek shade in the middle of the day, wear long sleeves, a broad-brimmed hat, and sunglasses, and use a broad-spectrum sunscreen with SPF 30 or higher. Broad-spectrum matters here because many drug reactions are triggered by UVA, which passes through clouds and window glass.

If a burn or rash appears, tell your prescriber soon and describe when it started in relation to sun exposure. A phototoxic burn is treated like a sunburn. A photoallergic rash may need a steroid cream. Your prescriber can decide whether the medicine should change.