Clinical Review

ABC of allergies: Avoiding exposure to indoor allergens

BMJ 1998; 316 doi: (Published 04 April 1998) Cite this as: BMJ 1998;316:1075
  1. Ashley Woodcock,
  2. Adnan Custovic

    The practice of avoiding exposure to allergens (allergen avoidance) for allergic diseases such as asthma is not a new idea. In the 16th century the Archbishop of St Andrews had a miraculous remission of his intractable asthma by getting rid of his feather bedding, and in 1927 Storm van Leeuwen created a “climate chamber” in Holland in an attempt to recreate the beneficial environment of high altitude sanatoriums. This article focuses on how to avoid indoor allergens in homes in temperate climates and the potential benefits for sensitised patients with atopic disorders.

    Amount of time that most Americans spend indoors, outdoors, and in transit

    Nowadays most people spend more than 90% of their lives indoors. Over the past 30 years, the home environment has changed enormously with the introduction of soft furnishings, fitted carpets, and central heating. Indoor ventilation has decreased—the rate at which indoor air is exchanged for fresh air is now 10 times lower than it was 30 years ago, with a considerable increase both in humidity and in concentrations of indoor pollutants and airborne allergens. As exposure to allergens is an important cause of symptoms in sensitised patients, reducing exposure should improve disease control. In spite of this, few patients in Britain with asthma, eczema, or perennial rhinitis, or any combination of these, are skin tested.

    Few patients in Britain with asthma, eczema, or perennial rhinitis receive advice on appropriate avoidance measures

    Characteristics of indoor allergens

    The predominant indoor allergens in Britain are from mites, cats, and dogs, and they have dramatically different aerodynamic characteristics. Mite allergens are present on large particles in beds, soft furnishings, and carpets, which become airborne only after vigorous disturbance and settle quickly. In contrast, about 25% of cat and dog allergens are associated with small particles <5 µm in diameter, which after disturbance remain airborne …

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