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, then it is an allergic skin condition.
Eczema is the most common skin condition, especially in children. It affects one in five infants but only around one in fifty adults. It is now 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 people with eczema have a food sensitivity which can make eczema symptoms worse. In about half of patients with severe atopic dermatitis, the disease is due to inheritance of a faulty gene in their skin called filaggrin. Unlike with urticaria (hives), the itch of eczema is not caused by histamine so anti-histamines do 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 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 them, or by touching clothing, pets or even gardening tools that have come in contact with the oil.
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 in the skin. Swelling in deep layers of the skin is called angioedema. There are two kinds of urticaria, acute and chronic. Acute urticaria occurs 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 or insect bites. Chronic urticaria is rarely caused by specific triggers and so allergy tests are usually not helpful. Chronic urticaria can last for many months or years. Although they are often uncomfortable and sometimes painful, hives are not contagious.
Angioedema is swelling 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. It typically does not have an identifiable cause. 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 treatment with antihistamines or adrenaline so it is important to go see a specialist.
Skin conditions are one of the most common forms of allergy treated and managed by an allergist / immunologist, a physician with specialized training and expertise to accurately diagnose your condition and provide relief for your symptoms.
Itching, redness and swelling are common to most skin allergies. Yet there are some differences that help in the diagnosis of specific conditions.
Itchy, red or dry skin. It may “weep” or leak fluid that crusts over when scratched, which means that it is also infected.
In infants, eczema often appears on the face. Children are prone to have the rash at the bends of the elbow joint, wrists, behind the knees and behind the ears. Adolescents and young adults typically have the rash in the same locations as children, as well as on the hands and feet.
Patients with the faulty filaggrin gene often have hand eczema with excessive little lines on the skin of their palms.
In many children, the exact cause of the eczema is not clear and treatment depends on regular use of moisturizer and topical medicines to dampen down the inflammation. One such treatment is topical steroids. In children where the skin is oozing, crusting and painful, an infection that needs treatment with antibiotics may be the primary trigger.
Infants and young children with more severe eczema should be evaluated for food allergy. It’s important to see an allergist / immunologist for diagnosis and management. It is often needed to receive input from a dietitian as well.
Food allergies causing eczema are much less common in older children and adults. If you are suspected of having eczema that is caused by a food allergy, a confirmed diagnosis requires avoiding the trigger food for about four weeks with the help of a dietitian before doing a food challenge under your doctor’s supervision to confirm that the food was actually causing the flare.
Urticaria is itchy, red and white raised bumps or welts that range in size and can appear anywhere on the body. Angioedema often appears on the face around the eyes, cheeks or lips. This deeper layer of swelling can also occur on hands, feet, genitals, or inside the bowels or throat. In acute urticaria, the welts disappear within minutes to a few weeks. Chronic hives last for months or even years.
In the majority of chronic cases, the exact cause cannot be determined. Routine testing such as general blood counts or screens are not cost-effective, nor do these tests make a difference in treatment strategies to relieve the symptoms. There are certain instances when allergy testing is helpful, especially when eating a particular food or coming in contact with a particular substance triggers symptoms of acute hives.