Allergy Triggers

The substance that causes the immune system to overreact is called an allergen. It takes more than just one exposure to an allergen to trigger nasal allergies. People with nasal allergies become sensitized, or allergic, to a substance only after repeated exposure. This can take weeks, months, or even years. Once you're sensitized, though, allergy symptoms develop every time you're exposed to that allergen. That's because your body mistakes a harmless substance for a harmful invader and wages battle against it.

If you have nasal allergies, you're sensitive to allergens that are specific to you. So what bothers you and causes your stuffy or runny nose, itchy eyes, and other symptoms may not bother someone else, even someone with nasal allergies. For instance, you may be sensitive to tree pollen. Someone else with nasal allergies may be sensitive to pet dander or dust mites.

Types of Allergies

There are two main types of nasal allergies: seasonal, which occur only at certain times during the year, and perennial, which occur year-round. Both cause the same symptoms. The primary difference is when and how often the symptoms occur.

Seasonal allergies are commonly called hay fever. They occur at specific times during the year and result in more than 10 million doctor visits annually in the US. Grass, tree or weed pollens are the most common triggers of seasonal allergies.

With perennial nasal allergies, symptoms don't change with the seasons. That's because the substances you're allergic to exist all year. They include cockroaches, pet dander, and mold spores. Or, you may be allergic to tiny parasites called dust mites that live in your house. As anyone who has cleaned house knows, dust has no season. The good news is that limiting your exposure to these triggers can usually control perennial nasal allergies.

Learn more about common triggers for:

• Seasonal Allergies
• Molds
• Dust Mites
• Cockroaches
• Pets

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Written by Karen Serrano, MD
Emergency Medicine resident at the University of Wisconsin-Madison.

Reviewed by Lisa V. Suffian, MD
Instructor of Clinical Pediatrics in the Division of Allergy and Pulmonary Medicine at Saint Louis Children's Hospital, Washington University School of Medicine
Assistant Clinical Professor in the Department of Pediatrics at Cardinal Glennon Children's Hospital, Saint Louis University
Board certified in Allergy and Immunology

Last updated June 2008