My twin 21 month olds always have a rash on their faces arms and legs....is it possibly a milk allergy?

Mat be: Also check that your bed room is not very hot and dry. Temp of room should never be higher than 72 f. Get a humidifier also.

Hard to say: Rashes can be triggered by illnesses to foods to environmental factors. Soaps/lotions, trips outside to play in nature, all add to the possibilities. True milk allergy is relatively uncommon, but if this is chronic and fits the features of eczema, a variety of foods can trigger or aggravate the condition in 1/3-1/2 of cases. If your doc has called this rash eczema, food allergy tests may be worthy