Eczema & Allergy. There are 2 types of dermatitis or eczema caused by allergy - contact dermatitis and atopic dermatitis. Contact dermatitis is like the rash you get with poison ivy and testing consists of a number of patches that are worn for 48 - 72 hours. Atopic dermatitis can be caused by food allergy and testing is done by skin prick with a drop of each suspected food and left on for 20 minutes.
Eczema Testing. Dr. Carter is right on point with various testing procedures for contact dermatitis and food-triggered eczema. Evidence suggests moderate/severe eczema in early childhood could be worsened by certain foods (usually highly allergenic foods like peanut, tree nuts, milk, eggs, etc.). Food triggers are not usually an issue in older adult eczema. See Allergist for details. Testing usually not indicated.