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 1, 2), 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!