Eczema and dermatitis (2)

 

Treatment of atopic dermatitis should first and foremost include repairing the skin barrier function to reduce allergen penetration. This can be accomplished by the regular use of barrier ointments. Food allergy is often an important factor in patients under the age of three, but diagnosing allergy in atopic dermatitis is full of pitfalls. These patients generally have very high total IgE antibody levels, rendering the use of allergy blood tests unreliable; in the presence of a large amount of IgE, non-specific IgE binding occurs and a large number of false positive reactions are seen. Many patients erroneously go on diets avoiding many foods based on these findings, whereas most patients are only allergic to less than three kinds of food. Skin prick tests are more reliable, but only if done during disease remission. Skin tests performed on inflamed skin will also result in a large number of false positive reactions. We therefore always treat the dermatitis first and do allergy tests once the disease is under control. Topical steroid is still the mainstay of treatment, but must be monitored carefully as overuse can further damage the skin barrier and might also lead to rebound inflammation. In patients whose skin is colonized with bacteria such as Staphylococcus, regular use of bleach baths can greatly reduce the frequency of exacerbations. Patients who require excessive amounts of topical steroid might benefit from a course of oral immunosuppressive drug therapy.

Contact dermatitis can affect people without the above mentioned skin barrier defects, but patients with atopic dermatitis often suffer from contact dermatitis as well. Contact dermatitis often occurs after prolonged or repeated skin contact with certain allergens. Plant resins known as urushiols, for example, can cause dermatitis in up to 70% of the population, given enough exposure. These resins are found on the leaves of plants such as poison oak, poison ivy or poison sumac. They are also used as varnish on furniture and lacquer ware. Some people are so sensitive that even contact with molecular amounts of the urushiol allergens can lead to severe outbreak. The most common contact allergen seen in clinical practice is nickel, which is found in a wide variety of household objects such as coins, fasteners, utensils and jewellery, and also in food. Dyes, preservatives, anti-microbials and fragrances found in skin care products are also common culprits. Rubber glove and detergent are common causes of hand dermatitis.

Avoidance is the most important treatment for contact dermatitis. The cause of the dermatitis must therefore be accurately diagnosed so that the patient knows what to avoid. This is usually accomplished by careful history taking, identifying the possible allergens the patient comes in contact with. The diagnosis should be confirmed with patch testing, as contact dermatitis is caused by a cell-mediated rather than IgE-mediated immune mechanism. Avoiding the relevant allergens is usually all that is needed to successfully manage contact dermatitis.

 

 

 

 

 

 

 

 

 

eference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.