Baby rash

My LO has a rash on her face hair and neck ! I am Strictly breastfeeding her and worried that it's me ! It flares up when she gets upset and when im feeding her so I've been told by some friends that it could be heat rash . When you look heat rash up online though it say it shows up where clothes are chest back and legs . Dunno if I should be worried or let it run its course. Any advise? She has no fever!