2,5 years old kid has foreskin infection(mild).is on cephalexin 250mg 3x a day. noticed very tiny petechiaes on his face near eyes and behind ears. could it be a side effect of cephalexin?

Many things are possible in life. Cephalexin generally does not cause any rash, but some people are allergic to it and develop a rash during or after the use of it. That said, rashes can happen for all sorts of reasons in any person. For example, some kids will get petechiae on the head after crying, vomiting, or straining to poop. Rashes are evaluated by visual exam, such as in a video Dr. visit.