Disadvantages of the diet
Otherwise, the keto diet is popular among people trying to lose weight, especially those trying to lose visceral fat, like the man in the case study. Anecdotal reports promote that the keto diet is effective in helping people lose weight relatively quickly, while also improving endurance and mental clarity. But robust clinical data to support these claims is lacking, and medical experts have raised concerns about long-term cardiovascular health, among other concerns.
There are also clear disadvantages to the diet. Ketones are acidic and if they build up too much in the blood, they can be toxic and cause ketoacidosis. This is a particular concern for people with type 1 diabetes and for people with chronic alcohol abuse. For everyone else, there is a list of common side effects, including nausea, vomiting, constipation, diarrhea, bad breath, headache, fatigue and dizziness. Ketogenic diets are also linked to high cholesterol and kidney stones.
But there is one side effect that is widely known, but little known and still a mystery to doctors: the “keto rash” or prurigo pigmentosa. This rash fits the man's case perfectly: red, raised, itchy bumps on the neck, chest and back, with areas of hyperpigmentation also developing.
The rash was first identified in 1971 in Japan, where it was mainly seen in women. Although it has been consistently linked to metabolic disorders and dietary changes, experts still don't understand what causes it. It is seen not only in people following a keto diet, but also in people with diabetes and in people who have undergone bariatric surgery or are fasting.
In a review this month, researchers in Saudi Arabia noted that a leading hypothesis is that high levels of ketones in the blood cause inflammation around the blood vessels, driven by a type of white blood cell called neutrophils, and this inflammation is the cause of the rash, which develops in several stages.
Although the condition remains poorly understood, effective treatments have at least been developed. The most common treatment is to take the person out of ketosis and give him/her an antibiotic from the tetracycline class. Antibiotics are designed to treat bacterial infections (which they don't), but they can also dampen inflammatory signals and thwart neutrophil activity.
In the man's case, doctors gave him a two-week course of doxycycline and told him to abandon his keto diet. A week later the rash was gone.
