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Keto rash is a side effect experienced by a small minority of people who follow a keto way of eating.
Unfortunately, in susceptible individuals, the only long-term solution is to raise carb intake in order to avoid deep ketosis. The precise number of carbs needed to prevent the rash likely varies from person to person but is typically outside of the ketogenic range.
However, a low-carb diet still provides many of the same benefits that a keto diet does, including excellent blood sugar control, weight loss, freedom from food cravings, and better overall health.
As keto diets continue to grow in popularity, greater numbers of people are enjoying their many benefits. Unfortunately, in some cases, adverse effects may occur as well. For example, keto rash is a condition experienced by a minority of those who follow a ketogenic way of eating. Read on to learn more about keto rash and strategies for resolving it.
What is Keto Rash?
The technical name for keto rash is prurigo pigmentosa. It's also referred to as Nagashima's disease because it was first described in 1971 by Japanese dermatologist Masaji Nagashima (1). Although it is most commonly seen in Japanese, it's also been reported in Korean and Middle Eastern populations, among others ( 2, 3).
Prurigo pigmentosa has been linked to several conditions, including H. pylori infection and autoimmune diseases like Sjogren's syndrome. In addition, it's been known to occur in people with uncontrolled diabetes and in those who fast or eat ketogenic diets ( 4, 5, 6). Keto rash has also been reported in at least one weight-loss surgery patient (7).
Based on the research to date and many anecdotal reports, very low intake of carbs or calories — both of which cause ketosis — can trigger keto rash in susceptible individuals. Indeed, researchers have known of a connection between ketosis and prurigo pigmentosa since the 1990s (8).
However, although ketogenic diets have been used in pediatric and adult epilepsy for decades, fasting and strict keto regimens have only recently achieved popularity among the general public for weight loss, diabetes, and other conditions. Because of this, keto rash hasn't received much attention until now.
What Are the Symptoms of Keto Rash?
Keto rash is an itchy, red rash that typically occurs on the torso, back, neck, and underarms. The rash is often symmetrical and usually appears within a few days or weeks of entering ketosis.
Its appearance has been likened to contact dermatitis, eczema, and impetigo. However, keto rash has a unique netlike pattern that is present from the initial stage through its resolution.
Stages of Keto Rash
The rash makes its appearance subtly, with mildly itchy raised bumps that are light pink in color (picture A).
After a few days, the bumps become papules, or clusters of small, hard red lesions, some of which may be filled with liquid or pus. Itching usually intensifies during this stage, although this seems to vary from person to person (picture B).
After another few days, the lesions become brown and crusty as the rash resolves. The affected skin is left with a light-brown net-like pattern known as reticular post-inflammatory hyperpigmentation, which may remain long after the rash has healed (picture C).
Photo source (picture A): Hawaii J Med Public Health. Treatment of prurigo pigmentosa with diet modification: A medical case study. Photo source (pictures B and C): Dermatopathology. Prurigo pigmentosa (Nagashima’s disease) — variations on a theme.
Although keto rash is usually confined to the front and back trunk, in some cases it spreads to the upper thighs. Very rarely, it may affect the forehead or extremities.
Although it can be unsightly and uncomfortable, keto rash itself isn't dangerous.
Why Does Being in Ketosis Cause a Rash?
At this time, it isn't known why some people develop keto rash while others who eat nearly identical diets and maintain similar levels of ketosis don't. Although it usually occurs during the keto-adaptation stage and often resolves relatively quickly, it can reportedly persist for several months or even years.
Some researchers have speculated that in susceptible individuals, ketones may irritate blood vessels, causing an inflammatory response that manifests as an itchy rash (7).
Other theories that have been discussed include diet-related gut microbiome changes that affect the immune system, skin irritation from acetone that is released in sweat, and an atypical response to low insulin levels that occur during ketogenic eating or fasting (7).
How Common is Keto Rash?
Because it hasn't been studied much, it's impossible to say how many people who follow ketogenic diets develop keto rash.
However, “keto rash” is a heavily-searched term on the internet, and there are several stories about people who have experienced it, including a detailed personal account by blogger BJJ Caveman. Although it occurs more frequently in Asians, it's also been reported in many other ethnic groups.
How Can I Get Rid of Keto Rash?
For some, keto rash is a temporary issue that goes away on its own. However, if you find that it remains even after you've been in ketosis for several weeks, you'll likely need to change your diet in order to resolve it. Here are a few strategies to get rid of keto rash:
1. Increase Carb Intake Until No Longer in Ketosis
A brief online search will reveal many stories of people who cured their keto rash by increasing carb intake to the point that they weren't in ketosis.
In one case, a 43-year-old woman developed keto rash about 3 weeks after restricting her diet to 20 grams of net carbs per day. The rash cleared up within a week, but it soon came back. Over the next few months, a pattern emerged where the rash would resolve, only to recur shortly thereafter. Although the woman tried to get rid of the rash by avoiding chemical irritants and potential food allergens like nuts, the rash didn't clear up for good until she increased her carb intake. On a higher-carb diet, she has remained rash-free for one year, as of the case study publication date, May of 2018 ( 5).
In another, a 17-year-old boy who had been following a nearly carb-free diet developed keto rash and was treated with higher carb intake and antibiotic therapy for two months. His rash resolved and didn't reappear at any time during 15 months of follow up, during which he continued the higher-carb diet ( 4).
Although the exact carb amounts used to treat the rash weren't reported in either case, the study authors made clear that it was significantly higher than ketogenic level. In all likelihood, their diets would no longer even be considered low carb.
However, in most cases, increasing your carbs to about 50-90 grams of net carb per day should be sufficient to clear up the rash.
Also, keep in mind that although keto rash does tend to recur, some people only experience it once. So if you want to reattempt keto in the future, it's possible that you may not develop keto rash.
2. Stay Out of Deep Ketosis
Interestingly, a recently published case study has shown that a more moderate low-carb intake may allow certain individuals to remain in mild ketosis while clearing up the rash.
In this case, an 18-year-old man with epilepsy was prescribed a strict 2:1 keto diet (which provides twice as much fat as protein and carbs combined) that was initiated and supervised by a registered dietitian. Although this led to a dramatic improvement in his seizures, he developed keto rash within a few days of starting the diet. After the rash worsened, his diet prescription was gradually changed to a 0.75:1 keto diet by increasing net carb intake from 16 grams to 90 grams per day, increasing protein intake from 70 grams to 95 grams per day, and reducing fat intake from 173 grams to 146 grams per day. Within days, the rash resolved, and it had not returned for 9 months at the time of the study publication. Moreover, the man has remained nearly seizure free without medication and has maintained a state of mild ketosis on the moderate-low-carb diet ( 5).
The study authors stated, “To our knowledge, we are the first to demonstrate that complete resolution of ketosis may not be necessary to successfully treat the rash, which is of particular importance in cases where the KD is therapeutically valuable as a successful treatment modality for medical conditions.”
While this is very encouraging, it's important to note that some people do need to remain in deep ketosis in order to manage epilepsy and other neurological conditions. Additionally, for many, even mild ketosis is unlikely to occur on a diet of 90 grams of net carbs per day.
3. Avoid Fasting and Extremely Low Carb Intake
Another option that might work is to continue eating a mildly ketogenic diet while avoiding fasting, which has been linked to keto rash in several people ( 6), including those who fast for Ramadan and other religious holidays (9).
In addition to avoiding fasting, do not severely restrict your carb intake. If you're suffering from keto rash, consider aiming for about 30-45 grams of net carbs per day.
This may or may not be successful, but it is worth trying if you don't want to raise your daily carb intake to the point where you're no longer in ketosis.
4. Address Other Contributing Factors
While increasing your carb intake will almost surely put you on the road to recovery, there are a few other things that can help speed up the process:
- Avoid getting overheated. Although it's impossible to stop sweating altogether, do your best to stay cool. Sweating exacerbates the rash, possibly because it releases more acetone through your pores.
- Wear lose-fitting clothing. As is true for many inflammatory skin conditions, friction can worsen keto rash. Avoid any clothing, jewelry, or other accessories that rub against your skin, especially during exercise.
- Manage stress. There's no question that stress affects many aspects of skin health, and people who've experienced keto rash often report that it intensifies during stressful situations.
5. As a Last Resort, Consider Antibiotics
If you need to stay in deep ketosis for therapeutic purposes (brain cancer, epilepsy, or another neurological disorder), you may want to consider having your doctor prescribe a short course of antibiotics to treat your rash.
Doxycycline and minocycline are the antibiotics that have been shown to be the most effective against keto rash ( 2, 4, 6). Although their purpose is to kill harmful bacteria, it's believed that certain types of antibiotics may help reduce inflammation and mediate the immune response which may trigger the rash ( 4).
However, keep in mind that antibiotics will only clear up an existing rash and cannot prevent new ones from developing.
What's more, antibiotics can adversely affect the composition of your gut flora and may lead to negative health effects, especially with frequent use. Ideally, antibiotics should only be used for serious infection when there is no other solution or treatment available. With few exceptions, increasing daily carb intake slightly is a much safer and healthier option, especially long term.
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