[Ilya shared here experience in the Comments section of the Treatment page:]
I started the keto diet in January 2014, after I hit the 117 kg mark and I decided that it is finally time that I should make a change. My weight problems in my opinion were coming due to my inability to fight sugar and carb cravings, which most of the days was leaving me at probably more than 300 grams of carb intake. For the following two months on the keto diet, I have experienced weight loss of around 22kg, dropping down to 95kg by following a very strict carb intake regime at practically zero. During the two months in which I have been on the keto diet I did not have absolutely any physical activity.
My experience with the keto rash started 2 weeks after I was on the lc/hf diet. At first I have started getting itches and small signs of rash under my left arm pit and above the arm pit on the inner side of the hand respectively about 2. At the time I was unsure what is causing it and I tried to treat in different ways. I implemented vitamins as a supplement, moisture and derm creams, oils and different things. Unfortunately for the next month and a half of the diet, while intensively keeping the rash area clean and treating it, nothing seemed to effect it. The rash kept getting worse with each day, with me receiving fresh limps on top of the already old and healed ones. Even that the rash was changing and evolving at those two spots, it did NOT spread to any other spots. For the 2 months in which I had the rash it was on a daily basis itching and hot(probably due to the scratching).
After slightly over 2 months on the keto diet and still with a rash I started intaking carbs and broke out of ketosis. I met a dermatologist one week after I stopped the keto diet, at which point there was absolutely no evidence of any active rash rather than the intense pigmentation of the skin that was left behind at the spot where I had the irritation, which made the doctor uncertain of putting a diagnosis of what exactly it was. I asked him if ithere could be a relation between the rash and the lowcarb/high fat diet I was doing and the answer was decisive no, which at this point leads me to the conclusion that doctors really do not have a lot of knowledge about the relation of this type of rashes and the keto diet. Back then I had a suspicion about the relation between the keto diet and the rash without me actually doing research, because I haven’t come to the idea to actually google the term “keto rash”. The intense pigmentation of the skin left by the rash dissapeared around one month and a half after I started intaking carbs and the rash resolving.
I have not had experience with similar type of skin condition until now (May 2016). In the middle of April I was comfortably sitting at 93kg and intensively training around 4-5 times a week doing crossfit for about 2 months, but I wanted to cut 4-5 kilos of extra fat that I have. As my will is very weak towards carb cravings and I tend to overeat on them I decided to give the keto diet a shot again as it keeps me sated and completely kills my cravings. I started my keto regime in the middle of April and for two weeks I have consumed <20 carbs per day, around 130-150g of protein and ~300g of fat. At this point in ketosis I can start to see the rash coming back at exactly the same spots as it was before, approximately after the exact same time after I started the keto diet as before, in the exact same pattern. I can only imagine the rash evolving in the same way as before, which if happens will convince me even more that the rash and the keto are going hand by hand, which I was suspecting back then.
I will continue the keto diet strictly for another week and if I see that the rash follows the same pattern as before I will include 50 grams of carbs per day in my diet to check if at this rate there will be an improvement.
This is a nasty side effect of the keto diet and a sad one. I will be very interested if there is an adequate solution or at least explanation of this. I am totally against using antibiotics for this as my experience has proven that I can easily fix it by introducing carbs and I am trying to avoid medicine as much as possible. I am by no mean expert in this, but I wanted to share my experience.