When you are exposed to an allergen or irritant, your immune system initiates an inflammatory response which can manifest on skin in the form of rash, itchiness, bumps, welts, and scaliness. Allergic reactions can be triggered by foods you are allergic to, direct skin contact with an irritant, or by asthma. Importantly, rashes resulting from a skin allergy are not contagious. Below are some common types of skin allergies.
Itchy, red bumps that blanch, or turn white in the center when pressed, is the hallmark symptom of hives. These itchy bumps can appear anywhere on the body and surface in response to allergy triggers including sweat, cold, medications, foods, insect bites, infections, and stress. Hives, also called urticaria, occurs when the body’s immune system releases histamine in response to contact with an allergen or foreign body. Excess histamine can lead to swelling at the surface of the skin. When the swelling occurs in the deeper layers of the skin, this is called angioedema, which commonly appears on the face. Approximately 20% of people have had hives at some point in their lives.
Urticaria can be acute or chronic. Urticaria is chronic when it occurs daily for 6 weeks or longer and is recurring. Chronic hives generally have a different cause than acute hives. Often, there is no identifiable trigger for chronic urticaria.
Swelling of tissues deep in the hands, feet, throat, eyes, or mouth is often indicative of angioedema. Often, angioedema is associated with hives and is caused by allergic reactions. In addition to swelling, angioedema may cause difficulty breathing and stomach cramps.
Allergic Contact Dermatitis
Skin contact with an allergen or irritant such as plants, perfumes or cheap metal jewelry may cause contact dermatitis. Allergic contact dermatitis appears as an itchy, bumpy, red skin that may also be swollen at the site of contact. Symptom onset ranges from a few hours to 10 days after exposure to the irritant. Because contact dermatitis rash is an allergic reaction, it is not contagious.
Eczema (Atopic Dermatitis)
Chronic and severe itching, redness, and scaly rash is often characteristic of eczema, also known as atopic dermatitis. Patients with eczema have dry skin that is sensitive to allergens such as dust mites, detergents, or fragrant perfumes. During eczema flare-ups, red and itchy patches of skin can become fluid-filled and erupt, oozing clear or yellow fluid. Eczema affects both children and adults, but it is more common in children. For infants, eczema rash typically appears on the face. For children and adults, the rash is found in more areas, including the wrists, knees, ears, and elbows. Adults also have eczema rash on the hands and feet.
Skin allergy diagnostic testing is often conducted by an experienced allergist or immunologist.
Your skin allergy doctor will obtain a detailed medical history and perform a thorough physical exam on you. Your doctor may order additional skin, urine, or blood tests to establish the cause of your allergic reactions. Because skin allergies can be associated with other food allergies, nasal allergies, and asthma, specific testing for these conditions may be done as well.
Patch testing is often utilized to identify the allergen triggering contact dermatitis. Small quantities of different, suspected allergens are placed on the skin in separate chambers and bandaged over. Approximately 2 to 4 days later, patches of inflammation may be present in certain chambers, indicating allergic reaction. Your allergist may ask you to come in again a week after the patch is removed to look for delayed skin reaction.
Managing & Treating Skin Allergies
Reducing exposure to allergens and irritants is the most effective preventative measure for minimizing risk of skin allergic reaction. Talk with your doctor about the best ways to manage skin allergies if they continue to occur.
Avoid Scratching and Itching
Avoid scratching skin rashes that itch, as scratching can lead to greater irritation and potential infection. Topical, moisturizing ointments can be used for itch relief. Wearing cotton fabric rather than garments made of wool or synthetic materials can help control itching.
Over-the-counter and prescription oral antihistamines are used to treat hives. They control symptoms by reducing itching and recurrence. Episodic urticaria may require stronger treatment with corticosteroids or immune modulators. For some patients, antihistamines are ineffective, and alternative treatment options should be discussed with an allergist.
Moisturizers & Topical Ointments
Mild cases of eczema can be treated with regular application of ointments and moisturizers like petroleum jelly. Moderate to severe eczema may require stronger topical steroid creams, prescription antihistamines, or calcineurin inhibitors
Soaking in a dilute bleach bath 1 to 2 times per week for no longer than 15 minutes at a time may help control eczema symptoms and reduce risk of infection. The recommended bleach bath ratio is ¼ cup of regular, non concentrated household bleach for every 20 gallons of water (a half-filled standard size bathtub). After the skin is patted dry, moisturize with cream or ointment.
In wet wrap therapy, a cotton dressing or gauze is soaked in warm water, then applied to dry skin that has been bathed and moisturized with topical cream. The wet wrap should be moist and not dripping with water. A dry layer should be placed over the wet wrap and can consist of a sock, plastic wrap, or cotton pajamas. The wet wrap can be left on for several hours at a time or overnight.
Immunotherapy With Biologic Agents
Patients 12 years and older with severe eczema may benefit from dupilumab injection under the skin. The injection can be done at home, twice a month, and may help control eczema symptoms for patients whose eczema is not well managed with topical therapies.
 American College of Allergy, Asthma & Immunology: https://acaai.org/
 Asthma and Allergy Foundation of America: https://www.aafa.org/