Could this be a milk allergy?

We just started putting a small amount of whole milk in Aiden's bottles a couple days ago - 2 ounces at first (of 6) and today 3 ounces of a 6 ounce bottle.  I just noticed that his trunk is covered in a light rash.  Not his arms, legs or face and no other symptoms.  He hasn't  had any other new foods yesterday or today that I know of (maybe at daycare but that would have been yesterday and I didn't see a rash then).  The only other thing is that I used a new detergent the last few loads but what he's wearing today wasn't washed with it so I don't think that's it.  He had a fever for a few days this week that's gone now so I'm assuming it's unrelated.

 What would you think/do?  Should I stop the milk until the rash fades and try again and see if it comes back?  He's had plenty of cheese, yogurt and cottage cheese that I'm unsure if this would be related to the milk.