Skin Allergy
Irritated skin can be caused by a variety of factors. These include immune system disorders, medications and infections. When an allergen is responsible for triggering an immune system response in the skin, then it is an allergic skin condition.
Atopic Dermatitis
Eczema is the most common skin condition, especially in children. It affects one in five infants but only 10% of adults. One explanation for eczema is thought to be due to “leakiness” of the skin barrier, which causes it to dry out and become prone to irritation and inflammation by many environmental factors. Also, some young children with eczema can flare with a particular food. In about half of patients with severe atopic dermatitis, the disease is due to inheritance of a faulty gene in their skin called filaggrin, although this is affected by your race and ethnicity. Unlike with urticaria (hives), histamine is not the only cause of the itch of eczema so anti-histamines may not control the symptoms. Eczema is often linked with asthma, allergic rhinitis (hay fever) or food allergy. This order of progression is called the atopic march.
Allergic Contact Dermatitis
Allergic contact dermatitis occurs when your skin comes in direct contact with an allergen. For instance, if you have a nickel allergy and your skin comes in contact with jewelry made with even a very small amount of nickel, you may develop red, bumpy, scaly, itchy or swollen skin at the point of contact.
Coming in contact with poison ivy, poison oak and poison sumac can also cause allergic contact dermatitis. The red, itchy rash is caused by an oily coating covering these plants. The allergic reaction can come from actually touching the plant, or by touching clothing, pets or even gardening tools that have come in contact with the oil.
Hives
Hives are an inflammation of the skin triggered when the immune system releases histamine. This causes small blood vessels to leak, which leads to swelling and itching. Swelling without itching in deep layers of the skin is called angioedema. There are two kinds of urticaria, acute and chronic. Acute urticaria occurs at times after eating a particular food or coming in contact with a particular trigger. It can also be triggered by non-allergic causes such as heat or exercise, as well as medications, foods, insect bites or infections. Chronic urticaria is rarely caused by specific triggers and so allergy tests are usually not helpful. However, in rare hereditary diseases that cause chronic urticaria, genetic tests are helpful. Chronic urticaria can last for many months or years. Although they are often uncomfortable and sometimes painful, hives are not contagious.
Angioedema
Angioedema is swelling without itching in the deep layers of the skin. It is often seen together with urticaria (hives). Angioedema many times occurs in soft tissues such as the eyelids, mouth or genitals. Angioedema is called "acute" if the condition lasts only a short time such as minutes to hours. Acute angioedema is commonly caused by an allergic reaction to medications or foods. Chronic recurrent angioedema is when the condition returns over a long period of time, with each episode lasting hours to several days. Most cases do not have an identifiable cause.
Hereditary angiodema (HAE)
Hereditary angiodema (HAE) is a rare, but serious genetic condition involving swelling in various body parts including the hands, feet, face, intestinal wall and airways. It does not respond to typical angioedema treatment with antihistamines or adrenaline so it is important to see a specialist to screen for HAE and other genetic conditions.