Not really - I’m looking into at present. I initially though the rash was a keto rash, even though it is not in the usual location on the trunk (mine is on my shins), so I thought the increase ketones from fasting may have been aggravating it. However, I have just finished 2 weeks back on a high carb diet, which usually quickly fixes a keto rash, and the rash is still present.
Another option I am exploring is oxalate dumping causing the rash, and I think fasting may also cause this.
There is quite a bit of information about gut biome and rashes as well. I think I have a healthy gut biome - I have not intestinal or digestion problems, I haven’t had antibiotics in about 15 years, my diet has never been very SAD, and I take probiotics every now and again (e.g., yakult or a probiotic yoghurt). The only time I had any signs of candida was when I was pregnant, last time almost 20 years ago.
This article on fasting references histamines and gut biome in fasting but antihistamines have made no difference to the rash. However, the article also mentioned a thing called Substance P, which I have never heard of before. So I’m currently looking into that.
I’m leaning towards it being an oxalate-related rash. One of the remedies is to increase calcium so I started taking a calcium supplement last weeks, and there has been some improvement, but it is not dramatically improved. I have also been applying topical cortisol cream for a few weeks, with varying results.
This week I am back on keto so I’ll see if it gets worse again.