Allergies develop when your immune system reacts to a foreign substance, which triggers the production of IgE antibodies in your body. These antibodies react with the foreign molecule and promote the release of histamine and other chemicals that mediate the symptoms of allergy. Symptoms vary based on the allergenic substance, however, skin rash is a common symptom of many different allergies. Consult your doctor if you have an unidentified skin condition, especially if it is associated with other serious symptoms such as breathing problems, wheezing and swelling of your throat and mouth.
Types
Allergies are divided into different groups based on the substance, or allergen, that causes the reaction. Allergic rhinitis is caused by pollen, dust mites, animal hair and other airborne allergens that usually cause an itchy and runny nose, swollen eyes and congestion. Food and drug allergies are caused by proteins and other molecules that trigger immune reaction and IgE production in your body. These type of allergies are usually associated with hives, swelling of the lips and/or face, wheezing and, in severe cases, anaphylaxis, while insect sting allergy can lead to hives, edema at the sting site, chest tightness and anaphylaxis.
Atopic Dermatitis
Atopic dermatitis, also known as eczema, is a hypersensitivity reaction that can be triggered or worsened by allergy to pollen, mold, dust mite or animals, according to the website MedlinePlus. The symptoms of atopic dermatitis include itchy skin, oozing blisters, crusting skin, inflammation and redness at the affected area and leather-like skin areas that occur after long-term irritation. Atopic dermatitis usually first appears on the face or scalp in infants and on the elbows and knees in adults.
Hives
Hives is another skin rash that can be triggered by an allergy. Hives appears as red or white raised welts, most commonly around your tunny, chest and back, according to Dr. William Sears, an associate professor of pediatrics at the University of California Irvine. Unlike eczema in infants, hives rarely appears on the face. Hives is a very inconsistent rash that can appear and disappear within 10 to 15 minutes, only to appear again on another part of your body.
Treatment
You can treat both hives and atopic dermatitis with over-the-counter oral antihistamines such as diphenhydramine. Although hives usually disappears on its own, taking an antihistamine immediately when the first symptoms appear can help reduce the impact of the rash. Atopic dermatitis can also be treated with hypoallergenic lotions that help moisten your skin and reduce the itching and inflammation. In some cases your doctor may also prescribe a mild steroid cream to help treat the rash.
