There are several different types of rashes that can form from an allergic reaction. In general, rashes have a red appearance, can form in little bumps or large elevated areas of skin, are itchy, can appear flakey, and maybe warm or tender to the touch. Common types of allergic rashes include: Contact Dermatitis • Appears hours to days after contacting an allergen • Has visible borders and appears where the skin touched the irritant • Skin is itchy, red, scaly, or raw • Blisters that weep, ooze or become crusty Allergic Eczema • May resemble a burn • Often found on hands and forearms • Skin is itchy, red, scaly, or raw • Blisters that weep, ooze or become crusty Drug Allergy • Mild, itchy, red rash that occurs hours, days, or weeks after taking a drug • Hives, swelling, itching, and difficulty breathing • Tiny purple or red dots on the skin If your rash does not fit the description of any of these symptoms, you should have your rash evaluated by a medical professional as soon as possible.