Pets in the home: Impact on allergic disease
- Elizabeth A Erwin, MD
Elizabeth A Erwin, MD
- Associate Professor of Pediatrics
- Nationwide Children's Hospital
- Thomas A E Platts-Mills, MD, PhD
Thomas A E Platts-Mills, MD, PhD
- Professor and Division Chief
- University of Virginia Medical School
Patients ask a variety of questions regarding the impact of pets on allergic rhinitis and asthma. These relatively simple sounding questions expose a challenging area of research, and the answers to these questions are still being investigated. This topic will review several concepts that have taken shape in recent decades and discuss how these apply to common patient concerns.
The measures that patients with pet allergies can take to reduce exposure to dog and cat allergens in the home are discussed separately. (See "Allergen avoidance in the treatment of asthma and allergic rhinitis", section on 'Pets'.)
In most epidemiologic studies, a strong positive correlation is found between sensitization to cat or dog allergens and asthma [1-4] and to a lesser degree, allergic rhinitis . In different cohorts, the odds ratio for asthma associated with sensitization to cat or dog ranges from 3 to 9.2, and the association is consistently highly significant. Therefore, it is important to understand whether living with a pet increases or decreases the likelihood of sensitization to pet allergens and ultimately, the risk of developing allergic disease.
When considering studies of allergic disease, it is important to understand the distinction between the terms "sensitization" and "allergy." Sensitization refers to the production of allergen-specific immunoglobulin E (IgE). Sensitization is usually demonstrated by skin testing or in vitro immunoassays for IgE to specific allergens (sometimes referred to as radioallergosorbent testing [RAST], although this term describes an antiquated form of the test).
Being sensitized to an allergen is not synonymous with being allergic to that allergen, because individuals may produce IgE to allergens in a given substance, but not develop symptoms upon exposure to that substance. Individuals are considered to have clinically significant allergy or allergic disease when they have allergen-specific IgE and develop symptoms upon exposure to substances containing that allergen. Thus, greater numbers of people are sensitized to an allergen than are clinically allergic to it. The variables that determine why some sensitized individuals have clinically meaningful allergic disease while others do not have not been fully identified. This is discussed in greater detail separately. (See "The relationship between IgE and allergic disease", section on 'Terminology'.)
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- IMPACT OF CAT EXPOSURE ON SENSITIZATION AND ASTHMA
- Immunologic changes
- Possible mechanisms
- IMPACT OF DOG EXPOSURE ON SENSITIZATION AND ASTHMA
- TIMING OF INITIAL EXPOSURE
- IMPACT OF ONGOING EXPOSURE
- CONFOUNDING FACTORS
- COMMON PATIENT QUESTIONS
- Primary prevention
- Established allergic disease in a patient with pets
- Other scenarios