Ok with formula but reaction to pure cow's milk?

[Driver8]

DS has been formula fed cince birth. I have never noticed an allergic reaction to the formula. We moved him onto cow?s milk when he turned 1 two weeks ago and he has come out with a severe rash including some blistery spots. We put him back exclusively on formula yesterday and his rash has almost completely cleared up. This could of course be a coincidence. Has anyone else had experience with a cow?s milk allergy but no reaction to formula?

Maybe try 'easing' him onto the cows milk by half milk/half formula or if he does has an allergy to cow's milk, try soya? If rash persists with milk, then best see your paed.