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Atopic Dermatitis
What is "atopic dermatitis?"Atopic dermatitis is a skin condition. It is a subtype of eczema that has allergy as a major contributor. It is almost exclusively seen in young infants and children. Anywhere from 1-3% of children will be affected. Almost 85% will have signs and symptoms of the disease in the first year of life. The good news is that more than half will resolve the condition by the time the child becomes two years of age. The remainder may see the end of the condition during the teenage years; a few will persist into adulthood. The Greek term "atopic" means out of place. This is a disorder that does not seem to follow all the rules of allergy. The disorder is the first manifestation of allergy and usually takes about 3 months to develop. It is best described as an itch that rashes rather than a rash that itches. If we can stop the child from scratching at the skin, the classic features would not appear. These children are miserable, they are uncomfortable, and they tend to substitute the pain of torn skin for itchy skin. The constant scratching causes breakdown, secondary skin infections, and when the body tries to repair the area, it becomes lichenified or leather like. They seem to be triggered by a number of things. Dryness, irritants like wool, and possibly allergens. A major contribution by allergists has been the association of foods with this condition. These foods include egg, wheat, soy, cow's milk, peanut, and fish. Some of these children may follow an allergy pathway and develop allergic rhinitis (hay fever) and asthma in time. The Symptoms of Atopic DermatitisThe classic feature is itchy skin. The skin is dry, flaky, rough, and can be secondarily infected and show oozing and crusts. Different areas are affected at different ages. In the infants, the classic areas of involvement are the face, cheeks, the backside of the arms (called the extensor surface) and the front side of the legs. As this progresses to the childhood presentation, the areas involve the inner folds of the arms at the elbows and behind the knees. Teenagers and adults may have more involvement of the hands feet, and back of the neck. In the infants, oddly enough, there are two areas that tend to be spared, the area about the mouth and nose and the diaper area. Testing for Atopic DermatitisCriteria have been established for the diagnosis of atopic dermatitis. Features that must be present:
Need to have two or more of the following:
Or present with 4 or more of these:
What is needed is a combination of clinical and laboratory data to make the call or diagnosis of atopic dermatitis. There is no one marker, however 85% will have an elevated IgE and 85% will have a positive skin test to egg. Despite all these suggestion, we diagnose atopic dermatitis because it looks like atopic dermatitis. The Visit to the Allergy ClinicOur approach is to perform a detailed history and physical examination on the child. Questions are asked about exposures and a detailed dietary history is gone over. Frequently, in atopic dermatitis, there is no apparent cause-effect relationship that the parent observes, however we are interested in what they think are triggers for the scratching of the skin. The allergy skin tests focuses on those six foods that have been established as contributory for almost 95% of cases. In some cases, there may be an aeroallergen that needs to be identified. Remember, that in infants and children, it takes time to develop symptoms from aeroallergens. Depending on where you live, pollen sensitization would take two to three years. We may consider testing for animal dander if the history dictates and for house dust mites. That flaky skin the child is shedding helps feed the house dust mite. There have been cases where the inhalation of an allergen has been associated with flaring of the skin condition. There have also been reports of molds that favor growing on our skin that may lead to lack of control. As reviewed in our posting on allergy testing, the child should be off all antihistamines prior to testing. Three days is usually sufficient, however if they can be avoided for 7 days that would be best. The selections for testing are (a total of 10):
Atopic dermatitis has taught us some important lessons about food testing. I was fortunate enough to be involved with some of these studies during my training at Duke University. Dr. Hugh Sampson is a pioneer in the world of food allergy especially as it applies to atopic dermatitis. His work has shown that a positive skin test may not be as helpful as a negative skin test for this condition. Children who had positive skin tests were challenged with the suspected food in what is called a double- blind test format. Only half the time did a food that was positive by skin or blood test cause a flare of the skin! His work supported the "negative" predictive value of a food skin test. What was shown was that with a negative skin test to a food, there was less than a 6% chance that the food would cause a reaction. So the negative tests help the best and the positive ones help only half the time. What is also well know about skin testing these children is that they may have large numbers of positive skin tests but no clinical relevance. They will show a positive test but no story to support a cause-effect relationship. It was also discovered that in the vast majority of cases it was one food that contributed to the problem. It was rare for there to be two or more foods that were proven to flare the condition. These children had large numbers of positive allergy tests to foods, but most of them were falsely positive. Facts about Atopic Dermatitis
TreatmentThere was at one time significant differences in how the allergists and how the dermatologists approach this disorder. Currently there seems to be consensus on many of the issues A typical program may look like this:Avoidance - if there are positive food tests, strict avoidance may help. The family is given lists of each food and information on how to read labels to identify the various other names for the offending food. We also try to contact the Food Allergy Network. If an aeroallergen is identified, specific avoidance is gone over. Avoidance will always be the most important therapy for the allergic child. Antihistamines - there is debate here; histamine released by the cells of the patient will lead to itch. If they itch, they will scratch and have the consequences of a flare. Most of the itch occurs at night. We try to use an antihistamine on a regular basis to block the histamine response. There are currently available a number of new wave antihistamines that are non-sedating, however in children with this condition, sometimes sedation is needed. Atarax is given at night. Bathing - yes the wet treatment here, twice a day with tepid water, hand lather using Dove, Tone, or Neutragena soap. Let soak for twenty minutes, and then pat dry. Ointments/creams - an ointment may be the way to go to start. They are heavier and greasier, but may penetrate better. Topical steroid ointments are used. Care must be taken about applying some of these to the face, axilla, and groin areas. Moisturizer - oil in water, water in oil what ever is tolerated to keep the skin moist. Other treatments - avoid wool, avoid dryness Newer therapies - the FDA has just approved a skin cream that seems to have great potential in this disorder. [Keywords: Atopic Dermatitis] |
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