What causes allergic rhinitis?

Updated: Jan 02, 2019
  • Author: Quoc A Nguyen, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

For practical purposes, allergens can be divided into seasonal and perennial groups.

Seasonal allergens are primarily pollens. In general, trees bloom in the spring; grasses, in the summer; and weeds, in the fall. Information about regional allergens can be obtained from manufacturers of allergy-treatment supplies, local botanic gardens, universities, and newspapers.

Perennial allergens of importance are molds, house dust, and animal danders. Although these allergens are present throughout the year, they tend to be more problematic during the winter, when people spend most of their time indoors.

  • Molds can be either indoor or outdoor allergens. Perennial symptoms that worsen in cool, humid weather suggest mold sensitivity. The major manufacturers of allergy-treatment supplies have lists of predominant molds in each region. Significant reservoirs of molds include indoor plants, refrigerator drip pans, areas under sinks, and compost piles.

  • House dust is a mixture of approximately 28 allergenic components. The actual major allergen appears to be a collection of degrading lysine residues.

    • For practical reasons, the component of house dust that most closely resembles the overall extract consists of dust mites (although they are much less immunologically potent than the overall extract).

    • The 2 major dust mites in the United States are Dermatophagoides pteronyssinus and Dermatophagoides farina. These mites thrive in warm (65-80°F), humid (>70% relative humidity) environments. They are abundant in mattresses, pillows, upholstered furniture, and carpets.

    • Another significant ingredient of house dust is decomposing cockroach body parts, which can be a problem even in buildings that appear to be free of the live insect.

  • A person does not need to own a pet to be exposed to dander, such as cat dander, which can cling to clothing and be brought into classrooms and homes. Dog dander, however, tends to be primarily a problem for its owner. The dander of other pets such as rabbits and hamsters is also highly allergenic.


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