The scientific community isn’t clear on what causes this and why this happens.  It also isn’t clear on why this only happens to some people and not others.

I’ve written previously speculating on potential explanations here and here, but again, these are just ideas, with no hard data available to favor one explanation over the other.

Suspected causes from the scientific literature:

Causes suggested by commenters:

  • Candida die off
  • Herxheimer effect
  • Toxins that are released from the fat cells during deep ketosis
  • Nutrient or micronutrient deficiency
  • Food allergy
  • Fungal infection
  • Histamine intolerance
  • Exogenous Ketones

Causes suggested by Dave Asprey:

  • Toxins released from fat cells (mercury, DDT, pesticides, endocrine disruptors)
  • Aggravated gut bacteria and fungi

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  1. Julie

    I can see the deficiency in nutrition may cause it. I’ve been on and off keto since 2014 and I’m able to keep the rashes away with multi-vitamins.

    1. (Post author)

      Is there a particular multivitamin you use?

      1. Julie

        I take “Rainbow Light, Women’s One Multivitamin”

        I’ve taken other vitamins, the ones you take however many through out the day and those didn’t work out too well..
        Also, just fyi, taking vitamins slowed down my weight loss progression.

      2. Julie

        I forgot to mention, Rainbow has vitamins for men, women, kids, prenatal, etc.
        When I went to the doctor, I was told that its most likely a vitamin B12 deficiency. AND I have gotten tested for allergies and that was not the case.

  2. Kat

    Hi Philip,

    I’m so glad you’ve created this site! I actually discovered your blog before ever getting the keto rash so when it did pop up all over my ribcage, right below my chest, I knew immediately what it was.

    I started my LCHF diet a little over a week ago. On average I was eating below 30g of carbs. Anyway, I was reading about the benefits of intermittent fasting and exercising on an empty stomach (supposedly it jump starts ketosis) and decided to do just that today. I skipped breakfast and did a high intensity workout. Since I work from home, I didn’t shower immediately after my work out and ate some fried eggs for lunch. I hopped in the shower after lunch and when I came out, I noticed the dreaded keto rash!

    Since I haven’t tested my blood or urine for ketones, I can’t be sure how long I’ve been in ketosis for. I heard it could take up to 3 weeks if you’re just starting out. I guess this keto rash confirms I have indeed reached ketosis (yay?). An interesting thing to add is since this rash is linked to diabetes (as I’ve read in multiple sites), I wanted to include that prior to starting my lchf ketogenic diet, I was diagnosed with having insulin resistance. I wonder if that has anything to do with it.

    Ketosis to me is like the holy grail of fat burning, increased HGH and optimal health. I really do not want to increase my carb intake because my goal for doing this diet in the first place was to reset my metabolic state and hopefully reverse my insulin resistance. I have lost 4 pounds in 8 days so that was a nice bonus. In the meantime, I will experiment with my diet and tweak my carb intake here and there to see what happens. I may just end up getting a prescription for one of the antibiotics mentioned here although in my eyes, antibiotics are terrible for gut bacteria and something I would really like to avoid. Which is worse, taking antibiotics to kill the rash and gut bacteria or increase carbs and not be in ketosis?

    1. (Post author)

      I too shared your fear about taking antibiotics… especially with regard to the gut bacteria. But there’s a solution to that. Just take the antibiotics for the 14 day course… then go bonkers with probiotics afterward to repopoulate your gut!

  3. Curious

    So, I get this rash way worse than any of the pictures I have seen on here. I get it all over my trunk, chest, and back..down to my butt. It forms an “M” shape on my abdomen, and it gets worse and worse the more I am low-carb. It’s really horrendous and painful, and I can’t sleep when I have it. I have decided that this is so not worth being low-carb, and I have increased carbs for it to go away.

    Let me just say that years before paleo, I had a fungal issue on some of these same areas. I had dark brown patches that would flake off, and I treated it with selsun blue. I thought it was over. Now, I have realized that my “itchy” hips that I have had for years have these same brown flaky patches, and I also believe this to be a fungal problem. ALSO, when this keto rash starts to go away when I introduce carbs and when the raised bumps flatten and the skin gets darker, that looks exactly like what I had before.

    I am saying this because I actually did a biopsy (the dermatologist cut a piece of my keto rash), and they tested to see what the rash is. All I got back is that it’s folliculitis.

    Furthermore, when I first went low-carb and had this rash, my face was as smooth as a baby’s bottom. This was amazing for I had acne before. However, that didn’t last very long for what seemed like literally over one night, I had hundreds of flesh-colored bumps all over my face. Low-carb or not, I have been dealing with what I thought was a different kind of acne for a few years now. I also had really bad cystic acne and pustules on my jawline in addition to an overly bumpy texture on my skin. I have never had this kind of acne before, and I am now writing this because I HAVE A THEORY. I am also about to test this theory, but I wanted to write down my skin’s history first.

    So, I had a fungal issue before, and this keto rash was diagnosed as folliculitis (also a fungal issue), and these bumps on my face may just be pityrosporum folliculitis (fungal issue). So, basically, I think this whole thing is somehow related to an imbalance of the natural bacteria on the skin. Internally, I have yet to understand what’s wrong with me, but I hope that I can at least confirm that it’s fungal by starting to use Nizoral shampoo, which has an active ingredient for fighting folliculitis.

    I hope someone else can chime in on this, because I always thought that the rash proved low-carb was dangerous for me, but if it gets worse, does that mean the fungus is fighting back or getting stronger? I have tried my best in the past to stick through low-carb and watch my rash spread and spread and get worse and worse. It lasted for a whole year before, and I just can’t do that again.

    1. Curious

      Might I also add that I went to another dermatologist before the one that did the biopsy, and he just brushed it off as contact dermatitis even though I was telling him that it’s not, and it’s due to my diet. He got kind of angry, and he had me take prednisone for two weeks, which did nothing.

      The dermatologist that did the biopsy was sure that it was something internal due to the rash being symmetrical, but she told me she can’t find the answer.

    2. (Post author)

      Right now there really isn’t any definite data out there linking this rash to fungus, so it’s hard to say if this means your fungus is getting stronger or not. But I too would be interested to see anyone else’s thoughts.

      1. Curious

        Thanks for your reply! Yes, that’s true. I just have a gut feeling that mine is, and it’s only been one day, but I used the norazol shampoo immediately after I bought it yesterday. I applied it all over my face and left it there for 10 min before washing off. It’s been ONE DAY, and I have not seen this kind of improvement in my skin in years. Literally, my bumpy skin is so much better. I am pretty excited about this, and I hope this proves that I do have pityrosporum folliculitis. I will keep using it on all of my areas that have this rash, and I hope I can recover. I don’t remember if I mentioned it in my previous post, but I have minor pityrosporum folliculitis on my shoulders (literally came up like 2 months ago). I also have my dark brown itchy spots on my hips (also another fungal problem). As for the horrible whole-body version I get when going low-carb, I don’t plan on testing whether using the shampoo will get rid of that, because I am honestly scared of going through that hell again when low-carb. But if it ever crops up, like if I am ever accidentally low-carb, I will for sure try treating it once again like a fungal issue. Oh, and this kind of fungus that I am talking about uses oils and fats on the skin as their food, even coconut oil (even though it’s anti-fungal). So, applying oils and cream to the skin will actually worsen it for me. Again, this is just my own theory, and I’m sorry that it’s not when I am actually low-carb and trying to attack that keto rash, but this honestly looks like the less aggravated version of the keto rash, and if my keto rash was analyzed to also be folliculitis, then everything is connected to a fungal issue for me. I don’t know if it means I have too much candida or what. I just thought I’d share this here, and I hope someone can try the norazol shampoo on their rash.

        1. (Post author)

          I definitely think it’s a great idea to share. We need as many people to share their experiences as possible! So thank you!

  4. Dian

    Hey George,There is no problem with etnaig heavy cream or sour cream each day on a keto diet. However, its important to remember that both of these foods are highly caloric (1/2 a cup of heavy cream contains over 200 calories). So, if your goal is weight and body fat loss you still need to make sure that these foods allow you to adhere to your daily calorie and macronutrient goals.

  5. Erika lemere

    Hey everyone. I’ve been following Keto fully for about 3 wks and have been fairly low carb for 2 months. I believe I was in ketosis fairly quickly since I lost weight quickly and had strong acetone breath. I was only eating 10g of net carbs. Over the last 2 days I have developed Keto rash on my right arm. It’s pretty significant. Only slightly on my left hand. I wonder if it’s because I introduced coconut. I’ve been eating coconut flour biscuits the last few days and that was the only difference in my diet that made it appear. I am even more strongly suspicious it’s from a coconut sensitivity because I tried “oil pulling” with coconut oil awhile back and my face similarly broke out. I now pull with sesame oil with no reaction. Anybody else notice this correlation with coconut products?

  6. Julie Gale

    I had an all over the face reaction that was buring and itchy. My skin peeled off. This was five weeks after being on LCHF, going on holiday and having to eat bread two days running. Having had none. We couldn’t trace anything that had been put on my face and neck. Off of bread and on LCHF it went away but I noticed a tingle in the same place it started befoe on a hot day. It had been hot when the original problem had started. I don’t know if I was in keto, had not been trying to be. Is this similar, would be good to get an answer, perhaps a little more carbs but then it was bread that seem to set me off.

  7. Doug

    For what it’s worth, when I go too high in my calcium consumption I get the red itchy rash, as well. When I go low carb I tend to do two things: eat kale for my carbs and vital vitamins and minerals like it was going out of style (100 mg per cup / 12% RDA) as well as what I get from a daily multi-vitamin (214 mg / 27% RDA). In addition, I’m also prone to taking more than I should of zinc, which is also known to cause rashes when over-consumed. It’s probably a good idea for anyone suffering the keto rash to take a look at whether they aren’t taking too much of one or both of these.

  8. Doug

    UPDATE: Rash improving…I think.

    Taking a day off from supplementation, I am finding the rash seems both to have become somewhat less itchy and gone down a little. It’s on my back so it isn’t the easiest thing to see with 100% clarity, but even this one-day result is enough to make me think I should back off the supplements and see what happens. My supplements are as follows:

    B Complex

    It’s possible I’m overdoing not only the zinc and magnesium, but the calcium contained in all the green vegetables I’m eating when combined with what’s in the multi. Possibly. In any event, I intend continuing on this way for at least a week before really gauging the results.

  9. Doug

    Rash appears to be even less itchy today, as well as softer to the touch. Because of it’s location on my upper back it isn’t the easiest to see whether the color is changing or whether it’s getting smaller, but I feel A LOT better than the other day when it was harder, more raised, and itched like the devil.

  10. Doug

    Rash very much faded in color, no longer itches. I think backing off all the supplementation was not the worst thing I could have done. What I’m thinking is, “problem solved.”

    1. (Post author)

      Thank you for your updates.

      Would you be interested in sharing your experience as a guest post?

  11. Cath

    Thank heavens I found you! I’ve been on a 16/8 daily fast for 9 months. I started that to manage my “weight creep” and then discovered the ketogenic diet. I’ve been reading the literature and watching conference videos (Phinney, Volek, etc.) for 2 months and am pretty convinced of the benefits of keto.
    HOWEVER, yesterday morning I woke up with an itchy rash on my lower back, symmetrical, but no fever or nausea, so I was ready to take a wait and see approach. Then I saw it on the inside of my forearms and freaked, went to the doctor. After a pretty thorough discussion of my recent activities, food intake, etc., she suggested that it was an allergic reaction and prescribed OTC antihistamines. I took 3 benadryl over the course of last night and woke several times to put an ice pack on my arms and hands to treat the itching. This morning I have lots of itchy, colorless bumps – they look like mosquito bites- on my arms and back.
    I am bummed, because keto is getting my weight down and I LOVE NOT BEING HUNGRY ALL THE TIME.
    Does this go away as the body adapts to keto?? I will stop the multivitamins.
    NB. I developed lichen planus on my legs 15 years ago in the tropics, but that is no longer visible, I have asthma related to airborne allergens, and family with psoriasis and dermatitis, but no diabetes.

  12. Dar

    According to Volek and Phinney, insulin is responsible for histamine control and is generally anti-inflammatory. My theory is that as you become keto-adapted, your insulin goes down, which allows histamines to run wild in your body and cause this rash in some people. This could also explain why it generally appears 2-3 weeks into ketosis instead of immediately (that’s about how long it takes for insulin to go down significantly), and why ‘carbing-up’ solves it (glucose intake causes insulin to rise again).

    My rash is flat and dry (no itching) and appeared exactly 2.5 weeks into keto. Last time that happened I stopped the diet for a while, but this time I’m choosing to take anti-histamines instead. We’ll see what happens.

    1. elizannlavet

      Quercitin is a natural antihistamine, vit. C and Bromelain boost the antihistamine activity of Quercitin. Bluebonnet makes a supplement with all three together. However, you might have to take as much as 6 in morning and 6 at night to see antihistamine results. Sites discussing Histamine Intolerance talk about a missing enzyme you can buy to increase antihistamine activity. The ketogenic diet itself is suppose to be anti-inflammatory, so the issue with insulin being anti-inflammatory is surprising.

      1. Dar

        Zyrtec helped me tremendously (it’s basically gone but I’m doing the full course just in case). I’m histamine intolerant in general, so your advice is much appreciated!

        Supposedly much of inflammation (leaky gut, free radicals etc) is a side effect of high glucose, where high insulin is a side-effect. But at certain threshold (t2 diabetics) high insulin starts to contribute to the problem.

    2. elizannlavet

      Quercitin is a natural antihistamine, vit. C and Bromelain boost the antihistamine activity of Quercitin. Bluebonnet makes a supplement with all three together. However, you might have to take as much as 6 in morning and 6 at night to see antihistamine results. Sites discussing Histamine Intolerance talk about a missing enzyme you can buy to increase antihistamine activity. The ketogenic diet itself is suppose to be anti-inflammatory, so the issue with insulin being anti-inflammatory is surprising.

    3. Josh


      interesting comment. Could you provide the source for Volek and Phinney claiming that insulin is responsible for histamine control? I would like to read (assuming it’s a written source; maybe it’s a video?) more on the subject.


  13. Pennie

    Has anyone ever had the ketorash appear on their scalp? I actually had posted on the Facebook page sometime ago and I thought I was done with the ketorash but…I have done low carb over the years and would break out in itchy rash just on my chest. I never stuck with it long enough for it to go away on its own. I have done 30 day fasts where I got no rash. However, last year in April I started zero carb. The rash appeared about the two week mark. I really think the issue is fungal so I refused to believe you had to add carbs to make it go away so I stuck with it. I can’t remember how long it took it to go away but in total imwas faithful to ZC for seven months. Unfortunately Thnaksgiving Day indecided to eat whatever and that day turned into months. I had several false starts trying to get back on ZC. FINALLY am two months into it again. Took at least a month for the rash to appear this time. Mostly chest and down to my ribs but a very narrow patch. That part is gone but my scalp still has sores and itches. I have actual knots on my head and behind my ears where lymphnodes are. However, as bad as it is it is still not as bad as the first time. The first time I had to wash my hair each morning because it was sticky from the ooze. It also itches but then hurts really bad. I do have a compromised immune system. I have hashis and I think I got that from living in a moldy home. I take no meds but I do take hashiscript, that one for only two months. An iodine protocol, which includes lugols iodine, selenium, Vit c, mag and sea salt. And I take turmeric and b complex and a multi sometimes. I only eat meat, mostly beef. No dairy eggs or anything else. I plan to just eat turkey on TG so as not to sabotage my efforts. I’m just curious that I have never heard of anyone else have scalp issues.

    1. Bst

      I have the same scalp issue, in the same areas, in the hair line above and behind my ears and at the back of my neck at the base of my hair line. It starts with an intense itch, swells, doubles the thickness of my scalp, the starts to ooze till the patch seems to burn itself out.
      I’ve had some itching in my arm pit and a tiny bit in my pubic hair as well but those areas do swell and ooze.

  14. Kittymouse

    Thank you or your helpful comments. I thought this was caused by an allergy to insulin as I am the 1st type of diabetes and I was given quite a big dosage. The itching was so terrible I thought it would drive me crazy. My doctor thought I wasn´t right in saying it would be an allergy to insulin but she did not know anything about the rash and didn´t see it previously and therefore she was not particularly helpful.
    However, I am not sure if the rash might be linked with a kind of insensitivity to insulin. Does anyone know about it? My feeling was I was swollen after the injection of insulin and itching seemed to be more severe. However, the effect of the injection seemed negligible.

  15. kittymouse

    I used only natural products to help it. Especially good seemed to me creams by Just (a Swiss company). I used their Thymian cream and also Tea tree cream which both have profound natural antibiotic effects. Later I also used Cordyceps orally which is produced by DXN or Tianshi. I often apply it everywhere where antibiotics should be administered. The antibiotics used orally are natural and don´t have a side effect on my body at all.
    However, before I learnt what it is, I suffered from terrible itching, indeed.

  16. bitchlet

    Since antibiotics seem to help a lot of people, it is likely that UV light could help also, since it is very effective at killing bacteria just like antibiotics. If the pathogenic bacteria reside on the skin surface, an UV lamp should be able to kill them off. I have a portable 311 nm UVB lamp that I use when I do keto. It seems to reduce, but not completely eliminate the rash. Bear in mind however that I am very conservative with the amount of UV exposure. I use the lamp for no more than 45 seconds on a single area. Longer exposure times could eliminate it completely, but I have yet to test that.


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