Possible milk allergy

Amanda 👨‍👩‍👧‍👦 • 27. Mom of two.Married. Dacien&Delaney 💙💖
I recently started giving my almost 1 year old a little bit of whole cows milk, to eventually be able to wean her off of formula. She has has started to get bumps on her checks and a red rash on her chin directly under her mouth. She's never had any type of skin problems. Could this be an allergic reaction to milk? She's been on formula for months with zero problems. 
( I haven't given her any milk in two days to see if it clears up, the redness on the chin is gone but she still has bumps on her cheeks) 
Thanks for any information you can give me.