Doctors linked the unusual rash to a rare side effect of the keto diet, though the cause remains unclear.
LONDON, Jan 24: A 20-year-old man in Taiwan developed a red, itchy rash across his chest and shoulders after starting a ketogenic diet, highlighting a rare but little-understood side effect of the low-carb, high-fat eating plan.
The man sought treatment at a dermatology clinic after the raised, itchy bumps persisted for a month, accompanied by patches of hyperpigmented skin. A biopsy revealed swelling between skin cells and inflammation around blood vessels, but tests for common skin conditions were negative, leaving doctors uncertain of the cause.
Medical staff traced the condition to the patient’s diet. Two months prior, he had switched to a ketogenic regimen, which shifts the body from using glucose to fat for energy. This triggers ketosis, a metabolic state in which fat breaks down into free fatty acids, then ketone bodies, which enter the bloodstream and serve as an alternative energy source.
Ketogenic diets are used clinically to manage drug-resistant epilepsy and some rare metabolic disorders, and studies are exploring their potential for obesity, type 2 diabetes, cancer metabolism, and neurodegenerative diseases. The diet is also popular among people seeking rapid weight loss and improved stamina or mental clarity, though long-term health effects remain uncertain.
Common side effects include nausea, vomiting, constipation, headache, fatigue, bad breath, high cholesterol, kidney stones, and, rarely, ketoacidosis—a dangerous buildup of ketones in the blood.
The man’s symptoms matched prurigo pigmentosa, or the “keto rash,” first reported in Japan in 1971. The condition, marked by red, itchy bumps with hyperpigmentation, is seen in people on ketogenic diets as well as in diabetes patients, fasting individuals, and those recovering from bariatric surgery. The exact mechanism is unknown, but a Saudi Arabian review suggests high ketone levels may trigger neutrophil-driven inflammation around blood vessels.
Treatment typically involves ending ketosis and administering tetracycline-class antibiotics, which reduce inflammation. In this case, doctors prescribed a two-week course of doxycycline and advised the patient to stop the keto diet. Within a week, the rash disappeared.
The case, published in the New England Journal of Medicine, underscores the need for awareness of keto-related skin conditions among healthcare providers and dieters alike.