A rash is a change in the normal appearance or feel of your skin. A rash may be painful or itchy, and it might make your skin red, bumpy, dry, cracked, blistered, swollen or warm. A rash can be caused by many different things, like a food allergy to milk or eggs or an infection. Sometimes it’s hard to know whether your rash including welts or bumps, itching or redness , are signs of an allergic reaction or something else. Eczema, contact dermatitis and hives are three common kinds of skin rashes that may be related to allergies.