Does Hydrochlorothiazide (HCTZ) cause sun sensitivity?

Does Hydrochlorothiazide Cause Sun Sensitivity?

Yes, hydrochlorothiazide definitively causes photosensitivity and is classified as a photosensitizing medication that should be discontinued immediately if drug-induced photosensitivity is suspected. 1

Mechanism and Clinical Presentation

Hydrochlorothiazide is a well-established photosensitizing thiazide diuretic that has been linked to photosensitivity reactions since shortly after its introduction in the 1950s. 2 The FDA drug label explicitly lists photosensitivity as a hypersensitivity adverse reaction associated with hydrochlorothiazide. 3

Common Clinical Manifestations

• Eczematous lesions in photodistributed patterns are the most common presentation of thiazide-induced photosensitivity. 2
• Photosensitivity reactions can manifest with heterogeneous clinical presentations and variable recovery times. 4
• In some cases, chronic photosensitivity can persist for months to years even after discontinuing the medication, representing a debilitating long-term complication. 5

Diagnostic Approach

When thiazide-induced photosensitivity is suspected, specific testing can confirm the diagnosis:

• Phototesting typically reveals abnormal responses to UV-A radiation alone or to both UV-A and UV-B wavelengths in most affected patients. 2
• Photopatch testing may yield abnormal results even when standard phototesting appears normal. 2
• Skin biopsy from UV test sites and lesional skin characteristically shows acute eczematous dermatitis. 5
• Phototesting in confirmed cases has demonstrated decreased minimal erythemal doses for UV-B and/or UV-A radiation. 5

Serious Long-Term Risk: Non-Melanoma Skin Cancer

Beyond acute photosensitivity, hydrochlorothiazide carries a substantially increased risk of skin cancer with chronic use:

• High cumulative doses (≥50,000 mg) are associated with a nearly 4-fold increased risk of squamous cell carcinoma (OR 3.98) and a 29% increased risk of basal cell carcinoma (OR 1.29). 6
• The highest cumulative dose category (≥200,000 mg) carries a 7.38-fold increased risk for squamous cell carcinoma and a 54% increased risk for basal cell carcinoma. 6
• There is a clear dose-response relationship between hydrochlorothiazide use and both types of non-melanoma skin cancer. 6
• The FDA drug label now explicitly warns that hydrochlorothiazide is associated with increased risk of non-melanoma skin cancer, predominantly squamous cell carcinoma in white patients taking large cumulative doses. 3
• For white patients taking cumulative doses ≥50,000 mg, the risk translates to approximately 1 additional squamous cell carcinoma case per 6,700 patients per year. 3

Management Recommendations

Immediate Actions

• Discontinue hydrochlorothiazide immediately if drug-induced photosensitivity is suspected, as recommended by the American Academy of Dermatology. 1
• Apply broad-spectrum sunscreen with SPF ≥30 to all exposed skin areas. 1
• Wear protective clothing including long-sleeved shirts, long pants, and broad-brimmed hats. 1, 7
• Avoid sun exposure between 10 AM and 4 PM when UV radiation is most intense. 1, 7

Alternative Antihypertensive Options

When discontinuing hydrochlorothiazide for gout or photosensitivity concerns:

• Consider switching to losartan as the preferred alternative, which has uricosuric effects and does not cause photosensitivity. 8
• Calcium channel blockers represent another alternative that does not adversely affect uric acid levels or cause photosensitivity. 8
• Other diuretics and antihypertensives have not been associated with non-melanoma skin cancer risk. 6

Ongoing Monitoring

• The FDA drug label instructs patients taking hydrochlorothiazide to protect skin from the sun and undergo regular skin cancer screening. 3
• Annual full-body skin examinations by a dermatologist are recommended for all patients with chronic photosensitivity. 1
• Monthly skin examinations during active phototherapy are recommended. 1
• Encourage patient self-examination for new or changing lesions. 1

Critical Pitfall to Avoid

Do not assume photosensitivity will resolve immediately upon discontinuation—chronic photosensitivity can persist for months to years after stopping hydrochlorothiazide, requiring prolonged sun protection measures and potentially specialized treatment such as PUVA phototherapy. 5