My baby was held by someone who had smoked marijuana (unknowingly to me) and a short time later my baby had a rash on her face. allergic reaction?

Perhaps; not to mar.: It is not unusual for babies to have rashes that come ; go ; some are caused by allergies, but it is impossible for her to have a reaction to marijuana by someone who had smoked it holding her. If she was allergic to peanuts she would not react to being held by someone who had eaten peanuts- she would need to be exposed directly. The same concept applies here. Also, allergy to marijuana is rare.