It may be a milk protien allergy even if your LO has had other dairy products. The same thing happened to my son. Everytime we gave him milk, milk based formula, goat's milk or ice cream he would get a pin prick, red bumpy rash on his face a chest. The other dairy products such as yogurt and cheese didn't bother him. We had to switch to lactose free formula. Even though his allergy was to the protien the lactose free formula (Lactose Free Enfalac) must have altered the protein becasue the rash stopped. Good luck!!! I hope this helps.