cow milk allergy

Any mummies LO has cow's milk allergy? I suspect my son (8MO) has it because after i fed him a couple of food that contains milk solids, his mouth area becomes red and bumpy. He is fully breastfed but since my supply is gg haywire, i tried to top up with goat's milk and he's showing the same allergy reaction. Already went to ask for a prick test at kkh but they said it can only be done in a month or 2 since it's not an important procedure during this pandemic. So what formula milk can i feed my son