Whenever the weather gets particularly hot and humid, I get an annoying irritation between the buttocks. Athletes call this "monkey butt," and the treatment of choice is called Anti-Monkey Butt Powder. I kid you not!
Excessive sweat from sports like cycling or horseback riding, long runs in heat and humidity (I'm a distance runner), or just sitting on your rear for long periods of time, can cause this condition. Baby powder, or the Anti-Monkey Butt Powder, and wearing natural fiber, looser clothing can help alleviate the problem and aid the skin in healing.