An allergic skin reaction, also known as a RASH, is a common symptom of an allergic reaction. It is characterized by redness, itching, and swelling of the skin. In some cases, it can also cause hives or blisters. Allergic skin reactions can be caused by a variety of allergens, including pollen, dust, animal dander, and certain foods. Treatment for an allergic skin reaction typically involves avoiding the allergen, taking antihistamines, and applying topical creams or ointments.