A 20-year-old man switched to a strict ketogenic (keto) diet hoping to lose weight and feel more energized. Within days, his skin erupted in a strange, net-like, intensely itchy rash—serious enough that his case was written up in the New England Journal of Medicine and reported by Gizmodo. This so‑called “keto rash” is rare—only around 300 cases have been documented worldwide—but it’s real, disruptive, and understandably scary if it happens to you.

In this guide, we’ll unpack what keto rash is, what may have happened in this man’s case, what science currently knows (and doesn’t know), and how you can protect yourself if you’re considering or already following a keto diet.

Medical image showing distribution pattern of keto rash on a person's torso
A rare case of keto rash described in the New England Journal of Medicine and reported by Gizmodo highlights an unusual side effect of very low-carb dieting.

I’ll focus on practical, evidence-informed advice: how to recognize warning signs, when to see a doctor, and how to adjust your diet safely—without overpromising or suggesting that keto (or any way of eating) is “one-size-fits-all.”


What Is “Keto Rash” and Why Is It in the News?

The condition often called “keto rash” is medically known as prurigo pigmentosa. It’s an uncommon inflammatory skin disorder characterized by:

  • Clusters of red, itchy bumps that may form a net-like or reticulated pattern
  • Commonly appearing on the chest, back, neck, and sometimes abdomen
  • Itchiness (pruritus) that can be severe and interfere with sleep and daily life
  • Brownish or darker patches left behind as the rash heals (post-inflammatory pigmentation)

In the recently reported case, the young man’s rash appeared soon after he dramatically cut carbohydrates on a keto diet. Once doctors recognized the pattern, they linked it to prurigo pigmentosa, which has increasingly been reported in people who enter nutritional ketosis—exactly what strict keto aims to achieve.

“Prurigo pigmentosa is rare, but clinicians are seeing more cases associated with ketogenic diets, fasting, and rapid changes in metabolic state.”
— Summary of recent dermatology literature up to 2025

While media headlines can sound alarming, it’s important to keep perspective: hundreds of millions of people have tried low-carb eating, and only a few hundred keto rash cases are documented. That suggests the condition is very uncommon, but for the people who do get it, it matters a lot.


Possible Causes: Why Might a Keto Diet Trigger a Rash?

Researchers haven’t pinned down a single, proven cause of keto rash. However, several plausible mechanisms have emerged from case reports and small studies:

  1. Ketosis and metabolic stress
    Many cases develop soon after entering ketosis—whether from a keto diet, prolonged fasting, or uncontrolled diabetes. Some dermatologists suspect that shifting fuel sources (from glucose to ketones) temporarily stresses the skin’s small blood vessels and immune pathways, triggering inflammation.
  2. Rapid weight loss
    Rapid fat loss can change hormones, inflammation signals, and how fat-soluble substances are released. Some case series note that patients often lose weight quickly before the rash appears.
  3. Nutrient or gut-microbiome changes
    Abruptly removing many carbohydrate-rich foods can alter fiber intake, gut bacteria, and micronutrient balance. Although evidence is limited, some clinicians wonder if subtle nutritional shifts might influence skin immunity.
  4. Heat, sweat, and friction
    The rash frequently appears on areas exposed to sweat and friction (upper back, chest, neck). In some reports, heat and sweating make it worse, suggesting an environmental component layered on top of metabolic changes.

In the case covered by Gizmodo, the man’s rash emerged shortly after he made a dramatic dietary shift into a very-low-carb pattern. When his diet and treatment were adjusted, the rash improved—supporting the idea that ketosis can play a role, at least for some people.


How to Recognize Keto Rash: Symptoms and Patterns

Because many rashes look similar, it’s easy to dismiss skin changes as “just irritation.” Keto rash has some distinctive features worth knowing:

  • Timing: Often begins days to weeks after entering ketosis (strict low-carb, fasting, or sudden carb restriction).
  • Location: Chest, upper back, neck, and sometimes abdomen and shoulders.
  • Appearance:
    • Small red bumps or raised plaques
    • Clusters that merge into a lace-like or netted pattern
    • Lesions may darken and leave brownish marks as they heal
  • Itch: Can be intense; scratching may worsen irritation and increase discoloration risk.
  • Course: May wax and wane, with new patches appearing as older ones fade.
Clinical photo of prurigo pigmentosa, the condition often called “keto rash.” Patterns and severity can vary. (Image: Wikimedia Commons, CC BY-SA)

Self-diagnosis is risky. Many other conditions—drug reactions, contact dermatitis, folliculitis, eczema, and more—can resemble keto rash. If you notice an unexplained rash while on a keto or very-low-carb diet, especially one that’s spreading or very itchy, it’s wise to speak with a clinician.


Who Might Be at Higher Risk for Keto Rash?

Because keto rash is so uncommon, we can’t definitively predict who will get it. But case reports and patterns suggest a few potential risk factors:

  • Entering deep or abrupt ketosis (very low carbs very quickly)
  • Rapid weight loss over a short period
  • Pre-existing inflammatory or autoimmune conditions (based on limited case observations)
  • High exposure to heat, sweat, and friction on trunk and neck
  • History of unexplained rashes with previous restrictive diets or prolonged fasting
“Most individuals adopting ketogenic diets will never experience prurigo pigmentosa. However, clinicians should be aware of the association, particularly in patients presenting with pruritic, reticulated eruptions on the trunk shortly after dietary change.”
— Dermatology review commentary, 2023–2024

The 20-year-old in the New England Journal of Medicine report appears to fit this pattern: a sudden, strict ketogenic diet, metabolic shift, and then a characteristic rash. Importantly, not everyone who diets this way will have the same experience.


Getting a Diagnosis: What to Expect at the Doctor’s Office

If you suspect keto rash, a healthcare professional—ideally a dermatologist—can help confirm what’s going on. A typical evaluation may include:

  1. History
    Expect questions about your diet (especially recent changes), supplements, medications, timing of the rash, and any other symptoms.
  2. Physical exam
    The clinician will look at the distribution, color, and pattern of the rash and may gently press or stretch the skin to better see the reticulated pattern.
  3. Possible skin biopsy
    A small sample of skin can help confirm prurigo pigmentosa and rule out other conditions. Under the microscope, PP has some characteristic features, though interpretation requires experience.
  4. Lab tests when indicated
    In some cases, blood tests to check blood sugar, inflammatory markers, or other conditions may be ordered, especially if there’s concern about diabetes or autoimmune disease.

How Is Keto Rash Treated? Evidence-Based Options

Treatment plans should be individualized, but several strategies have repeatedly shown benefit in case reports and clinical experience:

  1. Adjusting or easing out of ketosis
    In many published cases, reintroducing carbohydrates or moving from strict keto to a more moderate low-carb diet helped the rash improve. This doesn’t mean everyone must stop keto, but:
    • You and your clinician may decide to slowly increase carbs (especially from whole, minimally processed foods).
    • Some people choose to pause keto entirely until the rash fully resolves.
  2. Antibiotics with anti-inflammatory effects
    Medications such as doxycycline or minocycline (prescribed by a doctor) are often used to treat prurigo pigmentosa. These drugs are antibiotics, but in this context they’re mainly valued for their anti-inflammatory properties in the skin.
    Important: These medications have potential side effects (e.g., sun sensitivity, stomach upset) and are not appropriate for everyone. They should only be used under medical supervision.
  3. Topical treatments for itch and irritation
    Depending on severity, your clinician may recommend:
    • Topical corticosteroids to reduce inflammation
    • Soothing emollients or fragrance-free creams
    • Antihistamines for itch relief in some cases
  4. Cooling, gentle skin care
    Non-pharmacologic measures that may help comfort:
    • Lukewarm showers instead of hot water
    • Loose, breathable clothes to reduce friction
    • Avoiding harsh scrubs or scented products on affected areas

In the reported case and many others, symptoms improved once diet and medical treatment were adjusted. Some people are able to later return to a less strict version of low-carb eating without a recurrence; others choose a completely different dietary pattern that feels safer for their skin.


Considering Keto? Practical Steps to Lower Your Risk of Keto Rash

If you’re interested in the potential benefits of a ketogenic or low-carb diet—but understandably want to avoid surprises like keto rash—there are sensible, low-risk strategies you can use.

1. Avoid “all-or-nothing” overnight carb cuts

Instead of dropping from a very high-carb intake to deep ketosis in a day or two, consider:

  • Gradually reducing refined carbs (sugary drinks, sweets, white bread) over 1–3 weeks.
  • Prioritizing protein, healthy fats, and fiber-rich vegetables as carbs decrease.
  • Pausing or slowing down if you notice worrisome symptoms, including skin changes.

2. Aim for nutrient-dense keto, not just low-carb at any cost

A well-formulated ketogenic diet focuses on whole foods, not just carb counts:

  • Plenty of non-starchy vegetables (leafy greens, broccoli, zucchini, peppers).
  • Quality proteins (fish, eggs, poultry, legumes if they fit your carb allowance).
  • Healthy fats (olive oil, avocado, nuts) rather than only processed or saturated fats.
  • Attention to electrolytes and hydration, especially early on.

3. Monitor your skin during the first 4–8 weeks

Early awareness can prevent a mild rash from turning into a major problem:

  • Do a quick visual check of your chest, upper back, and neck a few times a week.
  • Note any new, persistent, itchy patches or patterns.
  • Keep a simple log of diet changes and symptoms to discuss with your clinician if needed.

4. Manage heat and sweat

Especially if you live in a hot climate or exercise intensely:

  • Shower promptly after heavy sweating.
  • Wear moisture-wicking, loose clothing around the trunk and neck.
  • Avoid very tight straps or gear that constantly rubs on the same area.
Person preparing a balanced low-carb meal with vegetables and healthy fats
A gradual, nutrient-dense approach to low-carb eating may support better tolerance and reduce the risk of unwanted side effects.

If Keto Rash Happens to You: Balancing Goals and Health

For many people, keto is appealing because it promises clearer thinking, better blood sugar, or weight loss. When an unexpected side effect like keto rash shows up, it can feel frustrating and unfair.

In practice, you and your healthcare team may consider several options:

  • Transition to a moderate low-carb or Mediterranean-style diet
    Often easier to sustain and associated with good evidence for heart and metabolic health, without pushing deep ketosis.
  • Cycle your carb intake
    Some individuals alternate lower-carb days with higher-carb days from whole grains, fruits, and legumes. There’s limited data about how this pattern affects keto rash specifically, so this should be done with medical guidance.
  • Pause keto and prioritize skin recovery
    For some, skin comfort and quality of life understandably take priority. Weight and metabolic health can still be improved through other nutrition and lifestyle approaches.
Before and after concept with a person looking at their skin in the mirror
With appropriate medical care and dietary adjustments, most reported keto rash cases improve over time, though lingering discoloration may take months to fade.
“Diets are tools, not identities. If a particular approach harms your skin, mood, or overall health, it’s okay to adjust course—even if it’s popular or worked well for others.”

What Does the Latest Science Say About Keto Rash?

As of early 2026, the scientific picture looks like this:

  • Rarity: Roughly 300 documented cases worldwide, though mild or unreported cases likely exist.
  • Association, not absolute causation: Strong temporal links between ketosis (from diet, fasting, or diabetes) and prurigo pigmentosa are observed, but not every person in ketosis gets a rash.
  • Response to treatment: Many cases respond well to dietary modification plus anti-inflammatory antibiotics, supporting an inflammatory mechanism.
  • Research gaps: We lack high-quality trials on prevention strategies, exact mechanisms, or which keto variants (e.g., higher-protein vs. classic) are lowest risk.

The New England Journal of Medicine case highlighted by Gizmodo adds to this growing pattern: keto rash is unusual but important enough that clinicians are more actively looking for it, especially as low-carb and ketogenic diets continue to be popular.

Partnering with a healthcare professional helps you weigh dietary benefits against potential risks, including rare side effects like keto rash.

Moving Forward: Making Keto (or Any Diet) Work Safely for You

The story of the 20-year-old man whose keto diet led to a rare rash is a powerful reminder: even health-focused changes can have unexpected side effects. Keto rash is rare, but real. For the small number of people who develop it, the impact on comfort and confidence can be significant.

You don’t have to navigate this alone. If you’re considering or already following keto:

  • Talk with a healthcare professional before major diet changes, especially if you have existing health conditions.
  • Introduce changes gradually when possible and pay attention to your skin and overall well-being.
  • Seek medical care promptly if you develop an unexplained, itchy, spreading rash.
  • Stay flexible—your health matters more than any specific label like “keto.”

If you’re worried about keto rash or are experiencing something similar right now, a reasonable next step is to schedule an appointment with your doctor or dermatologist and bring a record of your recent diet changes plus clear photos of the rash. Together, you can find a plan that supports both your metabolic goals and your skin health.

Your body is giving you information. Listening to it—even when the message shows up as an inconvenient rash—is one of the most powerful health skills you can build.


SEO and Metadata (Technical Overview)

Meta Title (recommended): Man’s Switch to Keto Diet Triggers Rare “Keto Rash”: What It Is and How to Stay Safe

Meta Description (recommended): A rare case of “keto rash” after a man switched to a ketogenic diet highlights an unusual side effect of ketosis. Learn what keto rash is, why it happens, symptoms to watch for, and practical steps to prevent and manage it safely.