Allergic Skin Reactions

Most people recognize that poison ivy causes an itchy rash in people who are allergic to poison ivy, oak, or sumac, but this type of contact dermatitis is only a small example of the type of allergic skin reactions that can occur. Contact dermatitis can also be caused by nickel, rubber or latex gloves, and other allergens. Like poison ivy dermatitis, the reactions may not occur immediately after exposure but rather within a few days. The rash is itchy, red initially, then flakey and sometimes oozing. Corticosteroids are necessary to decrease the intensity of the reaction.

Insect bites are an example of how a hive looks and feels. In most instances, hives are larger and occur over most areas of the body. Like insect bites, hives are typically very itchy but usually last for less than 24 hours in one area. Hives can be due to many different reasons: food and drug reactions, contact urticaria from a plant allergen, viral infections, insect bites and stings, and physical urticaria[LTW1] , are just a few reasons for hives. In many instances, patients who have chronic urticaria (hives that last longer than 6 weeks), have an autoimmune reason for their hives. However, in most cases of chronic hives, a cause cannot be found (idiopathic urticaria). Hives often respond to combinations of antihistamines but occasionally require stronger medications that reduce inflammation.

Angioedema is a term that describes swelling from an immune response. In most instances, patients may have a slight sensation of itching associated with the start of the swelling but typically the swelling is characterized by a dull ache and sometimes pain. Angioedema most commonly affects facial areas, specifically the lips and around the eyes but may affect any area.

A chemical called histamine is responsible for most episodes. Often angioedema will occur with urticaria and in this instance, the cause is the same with urticaria affecting the more superficial surface of the skin and angioedema the deeper parts that are supplied by blood vessels that leak fluid due to the reaction. Treatment of angioedema is mostly preventative with antihistamines taken on a regular basis.

Hereditary angioedema is rare but can result in extreme swelling that can cause suffocation. This condition is passed from one parent to one-half of the children but spontaneous occurrences occur in 25% of people without a family history of angioedema. This condition is caused by deficiency or dysfunction of an enzyme (C1-inhibitor) that keeps the complement system (which helps destroy bacteria) in check. As a result, a chemical called bradykinin is released and causes intense swelling that affects not only the skin (especially the face and hands) but also the intestines. This causes intense pain in the abdomen. Anabolic steroids are often used to prevent attacks of hereditary angioedema. Other injectable medications to treat acute attacks are currently being researched including replacement with C1-inhibitor concentrate which is now only approved for prevention.

Atopic dermatitis (AD) or eczema is a condition most often seen in infants and young children but can persist into adulthood. The hallmark of AD is intense itching associated with a rash that becomes red and then flakey. In some instances the rash may ooze and become infected with Staphylococcus bacteria, for which an allergic response develops to some of the bacteria’s toxins. This aggravates the allergic response and causes more itching which prevents healing of the rash. In 1/3 of children, a food allergy is the cause. Foods most likely to cause atopic dermatitis include milk, egg, peanut, wheat, soy, fish/shellfish, and other nuts. Avoidance of these foods will clear the rash. Treatment of AD revolves around keeping the skin moist and healthy by soaking in a bathtub daily and decreasing the use of soaps that wash off the natural oils that coat the skin. After bathing, lightly patting the skin dry and then immediately applying medication (usually topical corticosteroids or calcineurin inhibitors) to the affected areas. Then, a moisturizing emollient (lotion, cream, or ointment) is applied to the rest of the skin to help keep the moisture in the skin. Products that contain ceramides are available over the counter and help restore some of the lost oils that are lost during bathing. Antihistamines serve only to decrease the sensation of itching and do not affect the overall immune response.

Other conditions can masquerade as allergic skin disorders. A visit with a board certified (or board eligible) allergist can help define not only what the condition is and how to treat it but also how to avoid what may cause the condition. A listing of allergists can be found on the website of the Texas Allergy, Asthma and Immunology Society (www.taais.org).

The Texas Allergy, Asthma and Immunology Society (TAAIS) is a group of more than 220 board-certified Allergists/Immunologists in Texas.

An Allergist/Immunologist is a physician, usually an Internist or Pediatrician, who has had special training and experience in the field of Allergy and Immunology and who is considered to be an expert in the diagnosis and management of immune system disorders such as asthma, allergic rhinitis (hay fever), eczema, urticaria (hives), drug reactions, food allergies, immune deficiencies, and all general aspects of anaphylaxis.

A Board Certified Allergist/Immunologist is a physician who has passed the certifying examination of the American Board of Allergy and Immunology. A list of Board Certified Allergists can be found here. Those with “ABAI” under Board Certification are Board Certified Allergists/Immunologist.