Keto diet linked to itchy rash in JAMA Dermatology case report

A three-month itch and a rash that came back in crops turned out to be more than a nuisance for a man in his 30s on a ketogenic diet. Dermatology clinicians in Valencia, Spain, tied the eruptions to prurigo pigmentosa, a rare inflammatory skin disorder often called keto rash.

The patient had recurrent, very itchy papulovesicular lesions on the front of his chest and abdomen. The spots formed a reticulated pattern and, after fading, left behind residual redness and hyperpigmentation. He had no relevant medical history, and at first he did not report topical exposures, occupational or recreational allergens, or systemic symptoms that might have pointed doctors in another direction.

The clue came only after careful questioning. The man said he practiced intermittent fasting and followed a ketogenic diet, both of which can push the body toward ketosis. That detail mattered because prurigo pigmentosa is strongly associated with ketotic states, fasting, and ketogenic eating. The case report, published online on May 13, 2026 and indexed as PMID 42126849, was authored by Daniel Blaya Imbernón, Malena Finello, and Esther Diez Recio.

For keto readers, the point is not that every person who drops carbs will get a rash. Prurigo pigmentosa remains uncommon, and dermatology references describe it as a rare condition that most often affects the trunk, neck, and back. It is also known for leaving a reticulated hyperpigmentation pattern after the active rash settles. Although some references say it is reported more often in women, it clearly can affect men too.

The condition has been documented in a growing number of reports. A 2020 paper described prurigo pigmentosa induced by ketosis and noted online keto rash search results were already building. A 2021 Journal of Clinical and Aesthetic Dermatology report and literature review said the ketogenic-diet association had become common enough to merit closer attention. A 2024 review called ketosis an indisputable cause among the proposed triggers, even though the exact mechanism is still not fully understood.

Treatment usually focuses on the trigger and the inflammation. DermNet says adding carbohydrates back to the diet may help when ketogenic dieting or prolonged fasting is the cause, and that dapsone or tetracycline antibiotics can be effective during the inflammatory phase. That makes the warning sign worth recognizing early: a sudden, very itchy rash on the trunk after starting keto or pairing keto with intermittent fasting should not be brushed off as simple irritation.