Prurigo Pigmentosa – Thoughts on Pathogenesis

IdeaReader John was kind of enough to post this comment:

I also developed this skin rash after going into ketosis. After a couple of misdiagnoses I now even have a histopathology report that would support the diagnosis of prurigo pigmentosa (though no dermatologist I spoke with was aware of the association with ketosis). I did not look into the diagnosis until now, because it went away with sun exposure quite rapidly leaving behind hyperpigmented areas that are slowly fading away. I also had a low 25(OH)D level (Vitamin D) at that time. I have been sunbathing almost daily around solar noon ever since. My diet hasn’t changed. Has anyone had any luck with sun exposure? I would be very much interested in any ideas about the pathophysiology of the association between ketosis and prurigo pigmentosa.

As I was responding I started thinking more and more about his last sentence regarding the pathogenesis of why ketosis can spur this skin rash.

My ideas fall into 2 main categories:

Ketones Directly Cause the Rash

1. Something about ketones is causing an inflammatory reaction in our skin.  The ketones react to our skin like a drop of acid causing damage and inflammation.  I don’t think this is actually it because it should affect EVERYONE in ketosis.

2. Or maybe because our bodies are so unaccustomed to high levels of ketones, our immune systems haven’t had the chance to acclimate and thus over-react to them, like an allergic reaction.  This is possible since everyone’s immune system is unique and reacts to things differently.

Ketones Alter Our Physiology Which Indirectly Cause the Rash

We know for sure ketones change our physiology because once we are ketogenic, our insulin levels go down, our blood sugar goes down, we begin to lose weight, the overall body water goes down since we have less glycogen, other hormones are affected such as our thyroid hormone levels (Parts 12), and our cholesterol can either stay the same, go down, or go way up (Parts 1, 2, 3, 4), among many other things.  It could be any of these things.

1. A high LDL-P can possibly either directly cause the rash (not likely since not everyone with high LDLs have the rash) or elicit an indirect response.  The same goes for lowered blood sugar and lowered thyroid hormone levels.  Not everyone with low blood sugar and low thyroid levels have the rash.

2. Lowered levels of insulin.  This actually has some traction because one of the ways to make the rash go away is to reintroduce carbs into the diet, which raises the insulin.  Also in a few of the papers I reviewed (here and here) the rash went away after insulin was injected!

3. Another idea I had is that being in ketosis can alter our skin flora and our gut biome.  There is less glucose for organisms to feed on, so theoretically the ones that are more dependent on glucose for metabolism start dying off allowing others to grow.  Having altered flora can elicit an immune response.  I know there’s a lot of talk out there about ‘candida die off’ with ketogenesis or coconut oil intake.  I think this is also a real possibility because the current medically recommended treatment is to use antibiotics as I discussed in my prior post (my own feeling is still to try adding carbs back, and only turning to antibiotics if carbs don’t help).


I want to emphasize that all of this is pure speculation on my part.  I tried to include the supporting papers where I could but there are only a handful of papers on prurigo pigmentosa (and I reviewed almost all of them in my prior post) and the current scientific consensus is basically: we don’t know why this happens.

If anyone else out there has any ideas, please share!




17 Responses to Prurigo Pigmentosa – Thoughts on Pathogenesis

  1. Gabriele says:

    Great article.

    I’ve been in ketosis for almost a year now and having these weird rashes. I experienced your same pattern, but only during the night. The pigmentation showed up only during nighttime with heavy itching. In the morning, my skin was clean (but the rash appeared again the following night).

    When I added more carbs (sweet potatoes for a month to experiment in order to raise my thyroid levels), the rash went away. Now that I’m back in full ketosis, the night rash is back. I’m considering to up my carbs a bit (around 60-80 grams a day) to see if my skin improves.

    I also developed high LDL and hypothyroidism (now cured, and as a consequence my LDL dropped).


    • BJJ Caveman says:

      It’s interesting to see how we have such similar responses!

      Great to see that everything improved when you upped your carbs a bit.

      • Gabriele says:

        Well, I did some further adjustments and since I removed from my diet eggs, solanacee, nuts and seeds things are going even better. I’m gradually reducing carbs towards full ketosis (again!) and so far it seems there is no problem with the skin rashes. So I’m thinking more of an autoimmune reaction/allergy than a “a low-carb reaction” which I didn’t have anyway in the earlier months of my ketogenic regimen. I’ll comment again here once I have more insights.

        P.S..I published an article on my blog with photos of my abdomen (did you have similar rashes?) including your thoughts which for sure will help other Italian very-low-carbers. Saw you added my ping-back below. Thanks.

        • BJJ Caveman says:

          That’s great to hear.

          It’s possible that it can be an autoimmune thing… definitely keep us updated. The more information we have the better.

          After checking your website, it with a picture of the rash you posted, I can say that yes, some parts of my rash were similar to what you had!

          I really wish I took better pictures when I had it.

          You have a really nice looking website btw. Looks like there’s a lot of of great information… only wish I could read Italian.

          • Gabriele says:

            Maybe I should post my comment in the other (and more crowded post), but I’m continuing from where I started.

            So, in the meantime I’ve tried many things and rashes came back, always stronger in any attempt to stay very low carb.

            And I found why (in my case) the rashes were showing u when in ketosis. Cause after several test, I also did Doctor’s Data stool test wih parasitology x3 and discovered that I had (and still have unfortunately) Blastocystis hominis. This guest is usually non-pathogenic, but not always. Doctors know very little about it and 99% of the doctors who know it consider it commensal.

            It seems there are about 10 subtypes of B. Hominis, but very difficult to identify. And even the tests who do (very few), are not 100% reliable. And in particular, one of this subtype is associated to skin rashes. Will do a test to discover the subtype in a few weeks.

            And considering that Blasto is eukaryote, having a tiny mitochondria, can feed on both excess carbs (sugar) and ketones. This should be the reason why when you start producing ketones, blasto gets fed and proliferates. The same applies to excess sugar. So, according to Paul Jaminet, the best range, for whoever have an eukaryote organism (like Blasto and Candida Albicans) is to consume 100-150 grams of carbs per day.

            It can even survive without any food, especially if it has a biofilm, it can survive up to 43 days without any food.

            In the meantime, botanicals can work, but there is very little research and only in vitro. Oregano oil, berberine, colloidal silver seem to be promising. But it’s not easy at all. I’ve tried most plants, with little improvements and worsening of symptoms after stopping the supplements.

            The most effective therapy (82% successful) seems to be the triple antibiotic therapy created by Dr. Tom Borody at CDD in Australia. The first line treatment includes 3 abx for 10 days (current one includes: secnidazole, diloxanide furoate, septrim forte or Bactrim DS). I just finished it 3 days ago. I started to feel better from the 7th day onwards after some side effects. On Monday I felt perfect, like I had never felt in years. Today, symptoms are back. And even worse than usual. Especially skin rashes.

            Dr. Borody has a second line treatment (84% successful) for the ones who fail with the first line. So I’m considering this option. Even if dropping another atomic bomb in my gut is something I should think twice.

            The last resort is a colonic infusion (you need to go to Australia for this) with liquid antibiotics (100% successful).

            I have a friend, who had the same problem. Skin rashes when low carb. He did the parasitology test last month and came back positive with blastocystis as well. I don’t know if this applies to all cases. For sure to me and my friend yes. For whoever doesn’t find relief to skin rashes (but Blasto might trigger so many other symptoms), it could be interesting to take a proper stool test with parasitology (Doctor’s Data, Metametrix or PCR).

    • BJJ Caveman says:

      Thanks for pointing me to those sites. Paul Jaminet repeatedly stated that he had a ‘fungal skin infection’ that popped up whenever he went too low carb…. sounds eerily similar to Prurigo Pigmentosa. He never really explained how he knew it was fungal… in terms of response to antifungals or biopsy.

      The reason I doubt fungal disease as a cause are because all the histological studies only show generalized inflammatory changes within the skin. No signs of fungi such as hyphae, spores, etc..

      Also the medications used and shown to be effective are antibacterial… and not antifungal.

      Hopefully Paul Jaminet will answer your post and offer his thoughts on this! I’d certainly love to hear what he has to say.

  2. Rob says:

    Thanks for your research and on-going commentary. I’ve just flared up with a case of what seems to be this rash. (

    I have a general theory that seems to fit with the autoimmune occurrence and antibacterial treatment.

    For over 5 years, (with a carb-based diet) I’ve experienced a very similar rash caused by wearing an open-cell wetsuit while freediving. Specifically after wearing the wetsuit before it had completely dried out. It would clear up over a few days of not itching it, and not wearing a wetsuit.

    To prevent the rash, a Mirazyme solution is used to rinse the suit, and then allow to air-dry. (

    Fast forward 2 years, and I haven’t been freediving or wearing wetsuits.. no rash.

    I spend two weeks reducing carbs looking for induction to Nutritional Ketosis, and then have two weeks of low-to-moderate ketosis (0.6 – 1.9 mM/dL fasting serum BHB).

    I fell out for two days due to inadvertent carb intake, and resumed into a moderate-to-high serum level (1.9-2.4 fasting; 3.7 after a long run).

    On the day I went over 2.0 fasting serum, I went for a run with my heart rate monitor that had not been properly rinsed and dried from the previous use. Hours after that run, I have the rash on my chest at the location of the heart rate monitor strap!

    So, it could be that without a full course of antibacterials to fully kill all traces of the cause of the rash, high-ketone metabolism provides some skin environment where that bacteria can flourish.

    I’m going to persist with moderate-level ketosis for a few more weeks, so I’m not going to try the “carb” treatment just yet.

    I’ll probably pursue a Doxycycline prescription in an attempt to kill it off. Perhaps your carb re-feeding reduced the ability for the rash bacterium to grow, but it won’t kill it off completely.. maybe they live sub-dermally and only flourish when the conditions are right?

    I also hope that long-term keto-adaptation has purged the adipose tissue of the toxins that accumulate in the fat. Maybe the current fat burn rate is dumping a lot of those toxins back into my systems, allowing the rash bacterium to dominate some areas of skin??

    • BJJ Caveman says:

      Your rash looks just like mine! It’s interesting to see that the majority of the rash is in the center of your chest where the heart rate monitor was probably located… but there also seems to a line of the rash heading down to your belly button.

      Do you have any signs of the rash on your back or shoulders? Those seem to be common places for the rash to crop up.

      Please keep us updated on how things turn out with the doxycycline prescription!

      If the rash does not recur after you take the doxy… then it would really lend credence to the idea of a chronic subdermal bacerial infection that thrives in a ketotic environment.

      • Rob says:

        My spots were not beyond my stomach.

        I haven’t been to see the Doc yet, so no Doxy treatment to report on.

        However I tried the sunshine remedy. Despite moderate-to-high fasting serum levels, a big dose of strong sunshine killed all the rash, and I’ve been completely rash free for almost two weeks (without more deliberate sun exposure).

    • ema says:

      oh my god! finally i found someone who have the similar case with me.. i’m from malaysia btw.. so, here in asia, people are not too open to talk about this kind of problem. when i first start this atkins diet, everything seems fantastic because i loose my weight immediately. this rash just come out after 1 weeks i start my induction plan. i know i’m in a moderate stage of ketosis stage at 8.0 (i used an urinal strip test, it might not be accurate though). people NEVER warn me this kind of rash could be happening in the ketosis stage.. at first i thought that this rash is caused by sweating (i did some zumba dance), but, after search thoroughly through the internet, then i just realize that this rash associate with the ketosis stage in atkins diet. when i seek for medical consultation, they just prescribe me with clobetasol and hydrocortisone cream. i applied both of the cream (hydrocortisone in 1st week, and clobetasol on the second ween)but the rash did not go away!! but i did notice that the rash only appear at the top of my chest, little on the shoulder and at the back of my body. I’m so thankful that the rash did not appear on my face. it it is not always itchy, but when the time it does, i feel like rubbing the rash with fork!!!so today i’m going to start inducing a litle bit or carb (planning to consume some fruit yogurt because the probiotic in it might reduce the rash-causing agent.) will try to update u if there is effect on it.

      btw, i work as microbiologist. so, this type of matter make me freaking exited!! i’m sure this is not cause by fungus because i cannot see any sign of fungus growth on my skin (yucks!). but it might cause by bacterial and yeast infection that live sub-dermally or on our skin surface.

      • BJJ Caveman says:

        Oh nice! Thank you for chiming in! I would love to hear how things workout for you.

        Since you work a microbiologist, would you have experience with skin scrapings and staining and what not to see if you can figure out if you’re carrying any pathogens that can be causing this?

        Does the fact that doxycycline or minocycline make the rash go away bring up any ideas for you?

  3. […] what's causing it. Here are some links to posts I've written where I've thrown around some ideas Prurigo Pigmentosa – Thoughts on Pathogenesis – The BJJ Caveman Prurigo Pigmentosa – A Few More Thoughts – The BJJ Caveman But there isn't anything conclusive […]

  4. Ron says:

    I too have been afflicted after I had my ketones over 2 mmol for a few days while eating a ketogenic diet.

    I do not have an allergy to any foods, I NEVER get rashes and don’t have sensitive skin so I found this very strange.

    I think this is going to turn out to be an auto-immune issue and I think my wife might have figured something out- it might be a food allergy that only shows up when ketone are high.

    I have a question for those who have also experienced the rash:

    Were you eating macadamia nuts and/or heavy cream in large amounts?

    In my case I think it might have been the macadamia nuts as my consumption increased dramatically and for some reason, in the presence if high ketones, a food that doesn’t ever bother me crossed the threshold of becoming an allergen and caused me to break out in hives.

    It is the same reaction I have seen in a friend that is allergic to Mac nuts so I think it might be the case.

    I will of course continue to test and keep taking my ketones higher occasionally to see if I can acclimatize my immune system to this.

    Hope to hear from others if they were eating these two foods in large amounts.

    • BJJ Caveman says:

      I haven’t noticed much correlation between intake of macadamia nuts or heavy cream… The most amount of heavy cream I’d have would be 3-4 tbsp with my AM coffee… and this isn’t on a very consistent basis.

      Keep us posted on any patterns that you find!

  5. BJJ Caveman says:

    Please check out my newest project, for the latest updates on the keto rash!

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