Online Medical Resources: Understanding Skin Allergies

Skin allergies occur when an allergen (a foreign substance that causes an allergic reaction in the body) comes in contact with the skin. Common allergens include: metals (such as the nickel or chrome found in jewelry), latex (found in rubber gloves, rubber bands, and some bandages), chemicals (such as those found in perfumes, cosmetics, hair products, laundry detergents, and fabric softeners). Common allergens found outdoors include: poison ivy, poison oak, and poison sumac. Some allergic reactions occur immediately after the allergen comes in contact with the skin, while in other cases the reaction occurs hours or even days after contact with the allergen. To avoid many skin allergies, allergy sufferers should identify and avoid the allergen. Looking at the reaction’s location on the skin may help determine the point of origin: a rash under the arms may point to a lotion or deodorant, or a rash on the face near the hairline might point to a hair product. Some allergic skin reactions, such as hives and angioedema, can be triggered by food, airborne allergens, or even stress. Skin and blood tests can confirm a chronic allergy.

Eczema

Eczema, or atopic dermatitis, is a skin allergy that does not occur because of direct contact with an allergen. The exact cause of eczema is unknown, but eczema is most common in people with a family history of allergies. Approximately 70 percent of people with eczema have family members with allergies or asthma and 30 percent develop asthma themselves. Symptoms of eczema include: dry, scaly, itchy, red patches on the skin, particularly on the legs, face, arms, and scalp. These areas may crack, crust, and ooze. An estimated 20 percent of children and infants have symptoms of atopic dermatitis, but most outgrow the condition. In children, eczema usually begins with chapped patches on the cheeks and scaly patches on the legs, torso, arms, and scalp. Adults and older children experience rashes behind their knees, in the inner elbow, and on other areas of the body. Contact with irritants such as some chemicals or soaps, aeroallergens (airborne allergens, such as cat dander or dust) can trigger outbreaks in some people, and certain foods may trigger outbreaks in children. Prevent eczema flare-ups by moisturizing the skin and avoiding substances that irritate the skin or exacerbate the rash. If a rash occurs, do not scratch or rub it. Eczema symptoms can be treated with topical steroids or oral antihistamines to relieve itching, but there is no cure for eczema.

Urticaria (Hives)

Twenty percent of the U.S. population will experience hives at some point in their lives. Hives, or urticaria, are itchy, red, raised areas of skin. Hives can be any size, from small pin-pricks to large, irregularly shaped areas, and may appear on any part of the body. Acute cases of hives are triggered by allergens or irritants and go away in minutes, hours, or days. Chronic hives last for over six weeks. Acute hives are triggered by viral infections, contact with allergens, insect stings or bites, and stress. Chronic hives are rarely cased by contact with allergens but rather are an auto-immune reaction in which the body attacks its own cells and releases the histamines that cause hives. Physical urticarias are triggered by outside stimuli, such as cold, heat, pressure, or sunlight. Oral antihistamines and topical corticosteroids are used to treat outbreaks of hives. If the cause of the hives is known, outbreaks can be prevented by avoiding the allergen or physical cause.

Angioedema (Swelling of the Subcutaneous Tissues)

Angioedema refers to swelling beneath the skin. Angioedema may appear concurrent with hives or may occur without hives. Symptoms of angioedema include deep swelling, particularly around the lips and eyes and less commonly on the hands, feet, and genitals. In rare cases, angioedema may cause swelling of the throat, tongue, or lungs that can interfere with breathing. Swelling caused by angioedema usually lasts less than 24 hours. Acute cases of angioedema last less than 6 weeks and are often triggered by foods, infections, or medicines. Chronic cases of angioedema last more than 6 weeks and may be caused by autoimmune reactions, hormone disorders, or chronic infection. Hereditary angioedema is an inherited disease that is not caused by contact with allergens. If the cause of angioedema is known, patients should avoid contact with the allergen, food, or medication. Symptoms can be treated with antihistamines and oral corticosteroids. Severe cases of angioedema, particularly when the throat or lungs are affected, may require an epinephrine injection.

Contact Dermatitis

Contact dermatitis is a painful rash that occurs when an allergen or irritant comes into contact with the skin. Contact dermatitis can be divided into two types: irritant contact dermatitis and allergic contact dermatitis. Rashes caused by irritant contact dermatitis are painful rather than itchy and occur when an irritating substance contacts the skin. Substances such as detergents, solvents, chemicals, and cleaning fluids can cause irritant contact dermatitis. Reactions vary according to the strength of the substance and the amount of time it remained in contact with the skin. Wearing protective clothing, such as gloves, and avoiding contact with harsh or strong substances can prevent irritant contact dermatitis. Allergic contact dermatitis causes red, itchy, and blistered rashes when an allergen comes into contact with the skin. Allergens that commonly cause allergic contact dermatitis include: poison ivy, oak, and sumac, nickel, dyes, perfumes, latex and rubber, foods, and some cosmetics. Avoiding the allergen will prevent a reaction. When a rash occurs, it may last up to four weeks. Washing the area with a mild soap and cool water can remove traces of the allergen and prevent the reaction from spreading. Cool compresses may help relieve symptoms when the rash blisters. Calamine lotion and oral antihistamines may relieve itching.