It is strange that such a small baby had such severe erosive gastritis
causing gushing of blood!
Thank God he is OK now!
Go slow in dealing with him.
and cow's milk protein alergy can cause little amount of gastric bleeding only usually.
I am sure your doctor,or have done some tests and decided on this.
Wait for one year at least, then repeat the tests and see.
You can challenge with milk if your doctor advises after a year or so.
All the best