It's mold. I just got an answer on another website. Crawling, itching, stinging skin. I found an old AC unit a previous tenant left with black mold all in it. Find out the source it may be your AC unit or something else. I've been unable to sleep properly for 3 days because of this. I'm throwing out that AC.
Hello,
Aquagenic urticaria needs to be ruled out from your symptoms. It occurs due to hypersensitivity of the skin either to the water or to some other constituent present in the water (such as fluoride, chloride, other mineral etc). Treatment options include application of skin creams (such as capsaicin cream), phototherapy with UV light, antihistaminics, and other drugs (such as leukotriene-receptor antagonists, beta blockers etc).
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.