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Atopic Dermatitis and Indoor Allergens
AAIA Quarterly Volume 32 Fall 1996
AVOIDANCE MEASURES AGAINST INDOOR ALLERGENS: A SIGNIFICANT TREATMENT FOCUS IN ATOPIC DERMATITIS
Atopic dermatitis is a chronic inflammation of the surface layer of the skin, frequently associated with a personal or family history of related allergic disorders such as hayfever or asthma. Constant itching, scratching or rubbing lead to an itch-scratch cycle. In older children and adults, atopic dermatitis typically appears as redness, swelling and scaling/thickening in elbow creases, the back of the knee, and on eyelids, neck and wrists. The dermatitis may also be generalized.
Complications include secondary bacterial infection and swelling of lymph nodes near the site of infection. Frequent use of drugs applied to the affected skin exposes the atopic (allergically predisposed) patient to many potential allergens contained in the drug itself or in its other ingredients. These drugs can then lead to contact allergic dermatitis, aggravating the atopic dermatitis. Dry skin, which is common in people with atopic dermatitis, can also aggravate this condition.
Although the actual cause of atopic dermatitis is unknown, triggers include irritants (such as soap, laundry detergent), emotional stress, environmental temperature changes or humidity changes, bacterial skin infections, and wool garments.
There is significant evidence, however, that airborne allergens such as dust mites, cat dander, and cockroaches play an important role in atopic dermatitis. For example, researcher Deuell examined the level of mite allergen exposure from mattresses and bedroom carpets in a series of 51 pediatric patients with atopic dermatitis. He found that the majority of these patients were exposed to high levels of mite allergens in their homes. Eighty percent had positive skin tests to dust mite. He also found that levels of allergen-specific IgE antibody, as measured by a blood test called RAST, were very high in these patients, with most over 10,000 RAST units. RAST levels in a comparison group of allergic asthmatics presenting to the emergency room were between 800 and 5,000 units. He concluded that dermatitis patients may demonstrate extreme allergic sensitivity.
Researcher Platts-Mills found that the amount of antibody IgG in a sample of shed skin scales from atopic dermatitis patients correlated with the severity of their dermatitis.
Allergen avoidance has been associated with dramatic improvements in atopic dermatitis. One of the most important treatments is dust mite avoidance by covering mattresses and pillows with specially designed encasings which provide a barrier between the person and the allergen embedded in the mattress/pillow. Vacuum cleaning weekly while wearing a mask or equipped with a HEPA (High Efficiency Particulate Arrester) filtered vacuum, removing carpets and upholstered furniture, and reducing humidity below 45% (to prevent dust mite reproduction) are also key. Washing the bedding regularly at 55 deg C (140 deg F) is important even if the mattress is covered, particularly in children with atopic dermatitis, where there is a lot of skin shedding.
Cat allergen avoidance has also been associated with dramatic improvements. Even in undisturbed conditions, very small particles bearing cat allergen have been detected in the air. Researcher De Blay found a 100-fold higher airborne allergen concentration in a room with a carpeted floor compared to the same room with the floor covered with a plastic sheet. Removal of carpets is therefore highly recommended. Vacuuming with a HEPA-filtered vacuum and washing the cat remain important avoidance measures if the patient cannot be persuaded to give the cat up for adoption.
Cockroach is also being recognized as a significant indoor allergen which is airborne. Avoidance measures include reducing access to food by keeping counters clean and food in sealed containers. Reducing dampness is important and can be achieved by improving ventilation. Search for, and caulk, cockroach access points, like under sinks and between tiles. Chemical treatments are available, some of which may not be suitable for asthmatics. One which appears to be most successful and safe for use by those with asthma is the bait trap which contains hydromethylnon.
In summary, indoor allergens (especially dust mite, cat dander and cockroaches) are airborne and therefore come into contact with the skin. These allergens are becoming a focus of research attention as significant triggers of atopic dermatitis. Avoidance measures for these indoor allergens, although they require significant effort, are the best hope to be free of this sometimes debilitating skin condition.
References: M. Chapman, The Role of Indoor Allergens in Atopic Dermatitis, Clinical Perspectives in Immunotherapy. Proceedings of a Symposium, Vaudreuil, Quebec (Oct) 1993. The Merck Manual, 1992.
© Allergy/Asthma Information Association 1996
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