Answer:
It may be they aftershave or the perfume you use. Also it could be the bubble bath you use (if you do use some). Another suggestion is body cream, you could be allergic to these without knowing and the rash may have been building up for a while without you noticing. If it does not go away soon enough you could go and see a doctor as they will be able to give you a prescription to what you need to cure it. Good Luck! <3