I have just realised this is a very old thread, but was searching the net for info on split skin between the buttocks, I have IBS, AS, Fibromyalgia....for 20 odd years have suffered this butt crack split, it can get pretty painful and depressing having this, I notice all the comments, it started with me after I had kids, it seemed to particularly flare up just before my menstrual period, Dr's are no help just prescribing anti-biotic/steroid creams, one GP said it was a type of Eczema and often stress brings it on, the only time i ever seemed to 'cure' it was when i took high dose pro-biotics for a few months, it was amazing to be free of it, but i had money issues and couldn't afford to continue it and when i stopped taking it the problems returned bad as ever....going to try and give it another go...