Clive Anderson - AT THE DERMATOLOGISTTHERE IS evidence to indicate that atopic dermatitis (AD) is the first manifestation of a group of diseases called the atopic triad - eczema(dermatitis), allergic rhinitis and asthma. The atopic march is a term coined to characterise the progression of these atopic disorders with time. Some conditions become more prominent while others subside.
In general AD pre-dates the development of asthma and allergic rhinitis. It is suggested that AD is an entry point for subsequent allergic diseases. In a longitudinal study of 94 children over eight years, the severity of AD was found to be a risk factor for the subsequent development of asthma. In addition the prognosis of asthma was better in children without a history of AD. Between 70 and 80 per cent of children with AD and a family history of atopic diseases will subsequently develop allergic rhinitis and 50 per cent will develop asthma.
Evidence that allergen sensitisation through the skin evokes a systemic response leading to persistent respiratory disease has been demonstrated in animal models. These findings have led to the theory that the early treatment of AD should reduce the likelihood of development of the allergic disorders - halt the atopic march.
In the Early Treatment of Atopic Child (ETAC) project in Europe, treatment of infants with AD and a family history of atopy with cetrizine (a second generation antihistamine) was associated with a subsequent reduced incidence of asthma in subjects who became sensitive to dust mite. Other studies are currently underway to test the hypothesis that early intervention with pimecrolimus cream 1 per cent (Elidel) may not only provide long-term control of AD but also halt the atopic march.
In the mean time it seems rational that early treatment and good control of AD will not only ease the suffering of child and family but could slow the appearance of other atopic diseases such as allergic rhinitis, asthma and food allergies.
SKIN MOISTURISERS
The basis of good treatment of AD still remains the maintenance of good skin hydration. Atopic skin shows enhanced transepidermal water loss. In addition, the surface lipids on the skin are reduced. Hydration of the skin is best achieved through soaking baths. Medicines and moisturisers should be applied immediately after bathing. Certain moisturisers improve skin-barrier function and reduce its susceptibility to irritants.
In general, the greasier the moisturiser the better for the skin. Avoid moisturisers with perfumes. The frequency of application is important, the more often the better for the skin. Persons with AD have a low threshold for skin irritation. Avoid irritants such as soaps and detergents. Perfumed products are often triggers for AD. Changes in temperature and humidity can trigger the disorder and occlusive clothing should be avoided. Loose fitting cotton or cotton blend garments are better tolerated.
Food allergens play a significant role in some patients with AD. It is estimated that one-third of children with AD have a food allergy, with the common allergens -- milk, eggs, peanut, soy, wheat, and fish accounting for 90 per cent of allergens.
Topical corticosteroids remain the mainstay of treatment for AD. They are effective in reducing inflammation and itching. The choice of topical steroid prescribed will depend on the severity of the episode and the area affected. Because of possible local and systemic side effects with steroid use, they are generally used for short periods only and the lowest strength that will do the job is prescribed.
Concern over the side effect profile of corticosteroids has prevented their use as maintenance therapy. However, several studies have shown that once control has been achieved with a once daily regimen, long-term control can be safely maintained with twice weekly application of a topical steroid.
The topical calcineurin inhibitors are an important new class of medications that have been shown to have good efficacy in the treatment of AD while avoiding the adverse side effects of long-term steroid use. It is hoped that these new non-steroidal topical agents will offer improved long-term management of AD. Atopic dermatitis is a common relapsing skin disorder. The severity of the disease may be a risk factor for the development of other allergic disorders. Good long-term management of AD may reduce the likelihood of the development of these disorders.
Dr. Clive Anderson is a Dermatologist and Venereologist; email: yourhealth@gleanerjm.com.
