Estrogen Use Raises Rare Sun-Triggered Skin Disorder Risk 2.5-Fold

Estrogen-containing contraceptives carried 2.52 times the odds of porphyria cutanea tarda (PCT) in a Danish registry study of 438 women with the rare blistering skin disorder, published in JAMA Dermatology.

The case-control analysis drew on Danish health registries from 1995 through 2024. Researchers identified 438 women with newly diagnosed PCT — median age 61.16 years — and matched them to 43,800 controls. They defined estrogen exposure as at least one filled prescription for an estrogen-containing medication in the year before diagnosis, and adjusted odds ratios for comorbidities including HIV infection, liver disease, smoking-related conditions, and alcohol or drug misuse.

The findings give population-level weight to an association that smaller studies had only hinted at: estrogen as a contributor to PCT, a photosensitivity disorder that causes lesions and scarring on sun-exposed skin.

What did the study find by formulation?

The strength of the association tracked the type of estrogen product. The numbers from the adjusted analysis:

• Estrogen-containing contraceptives: 2.52 times the odds of PCT (95% CI, 1.67–3.82)
• Estrogen-only hormone therapy: 1.58 times the odds (95% CI, 1.23–2.03)
• Combined estrogen-progestogen therapy: 2.18 times the odds (95% CI, 1.53–3.11)

Route of administration mattered. Oral estrogen-only hormone therapy was associated with 2.44 times the odds of PCT. Vaginal estrogen and other non-oral formulations, including transdermal patches, showed no statistically significant association.

The pharmacology offers a plausible explanation: transdermal estrogen enters the bloodstream through the skin and skips the first-pass processing by the liver that oral medications undergo. But the data can't settle the question. Only seven patients with PCT had used non-oral, non-vaginal estrogen formulations — too few to draw firm conclusions about the safety of those products.

What is PCT and who gets it?

PCT affects an estimated 5–10 people per 100,000. Though rare, it causes skin fragility, blistering, liver damage, and excess hair growth on areas such as the face. A genetic predisposition can set the stage, but most patients carry more than two contributing risk factors. The list includes iron overload, heavy alcohol use, smoking, and estrogen exposure.

Clinicians managing persistent or difficult-to-control PCT should review the patient's estrogen use as a possible contributor, experts said.

Cory Simpson, MD, PhD, an associate professor in the Department of Dermatology at University of Washington Medicine in Seattle, who was not involved in the study, put it in practical terms. "If your patient comes to see you with blistering lesions on their hands, especially after sun exposure, and dark urine, PCT should be on the differential if they are taking oral estrogen," he said.

Should prescribing change?

Not broadly, according to Rebecca Karp Leaf, MD, an assistant professor at Harvard Medical School and co-director of the Mass General Brigham Porphyria Center in Boston, who was also not associated with the study. Given how rare the disease is, she said the findings give no reason to discourage estrogen prescribing across the board.

"I wouldn't avoid starting somebody on a combined oral contraceptive pill in her twenties because of a risk of PCT," Leaf said.

For women with a PCT history and severe menopausal symptoms, Leaf suggested transdermal estrogen as a reasonable option once the disease is in remission — with close monitoring for new lesions and changes in urinary porphyrin levels.

The sources cited in the original report declared no conflicts of interest. Larger cohorts of non-oral estrogen users will be needed before transdermal formulations can be confidently called lower-risk, but the registry data already give dermatologists a concrete reason to ask about oral estrogen when PCT appears on the differential.