Unexpected Keto Diet Effects

A 20-year-old man’s experience with the keto diet brought unexpected changes to his body, though not quite what one would typically anticipate.

This week, the New England Journal of Medicine reported on how the man developed a rare skin condition—often triggered by the keto diet—that resulted in itchy rashes covering his neck and chest. While the symptoms can be alarming, the condition is manageable if the individual can be persuaded to stop following the diet.

Keto Rash

The case was shared as part of a recurring segment in the NEJM focusing on unusual medical images.

The otherwise healthy young man sought dermatological help four weeks after noticing a strange rash. He informed the doctors that he had begun the keto diet to lose weight about two months prior.

This skin issue is formally known as prurigo pigmentosa, but it’s often referred to as “keto rash.”

Researchers are still figuring out the exact reasons behind its occurrence, but it seems closely connected to a state called ketosis, wherein the body primarily uses stored fat for energy instead of glucose. Keto diets promote ketosis through a significant reduction of carbohydrate intake, though other medical conditions can also contribute.

The rash typically develops in several stages, starting with small, itchy red or purple bumps on the neck, chest, and back. These initially minor bumps can enlarge into a distinct net-like pattern on the skin. Occasionally, they might fill with fluid and crust over, resembling blisters. While the itching may diminish and the rash might fade over time, it can come back, often leaving darkened spots behind as reminders.

Rare and Resolvable

Interestingly enough, keto rash is a fairly uncommon consequence of entering ketosis.

A 2019 study noted that only about 300 cases had been recorded globally at that point, with merely 20 cases in the United States. Most reports have been among women of East Asian descent, especially in Japan, yet this recent case highlights that it isn’t exclusively limited to that group.

Despite its rarity, the occurrence might be increasing as the keto diet gains popularity. Healthcare professionals might mistake the rash for more common skin issues like eczema due to its infrequent presentation. However, once identified, it’s typically straightforward to treat.

The rash usually resolves when a person exits ketosis, which may take a few weeks. In many instances, this means discontinuing the keto diet (cases not related to keto generally resolve independently). Tetracycline antibiotics can be effective in managing symptoms, owing to their anti-inflammatory properties. As for the young man in this report, it remains unclear whether he followed the advice to quit the keto diet.

Odd rashes aren’t the sole strange side effect connected to popular diets. Last January, there was a report about a man whose extreme “carnivore” diet, rich in cheese, butter, and meat, caused his hands to visibly seep cholesterol.