What Causes Seasonal Allergies?
Understanding seasonal triggers
Hay fever. Seasonal allergies. Allergic rhinitis. Whatever you choose to call it, the symptoms of this common immunological disorder affect about 40 million people in the United States alone.1 But what causes the body's immune system to attack otherwise harmless substances such as pollen and mold, resulting in congestion (stuffy nose), rhinorrhea (runny nose), itchy nose, sneezing, and a host of other bothersome seasonal allergy symptoms? And what are some of the common allergens that can cause your seasonal allergy symptoms? These are the topics we'll be covering below.
Why me?
Genetics and environment both play a role in determining whether a person will develop seasonal allergies, with family history being the number-one predisposing factor.1 This genetic tendency, called atopy, refers to the body's capacity to produce immunoglobulin E (IgE) antibodies2. During a process called sensitization, these antibodies mistakenly identify certain allergens as invaders — and as a result, the immune system launches an allergy attack the next time the patient is exposed to those allergens.3
Common causes of seasonal allergies
Both outdoor and indoor allergens can trigger the symptoms of allergic rhinitis. Common allergy causes include4:
- Trees (ash, birch, elm, hickory, maple, oak, poplar, sycamore, and walnut)
- Grasses (Bermuda, orchard, red top, sweet vernal, and timothy)
- Weeds (pigweed, ragweed, Russian thistle, sagebrush, and tumbleweed)
- Molds (alternaria, aspergillus, and cladosporium)
- Dust mites
When outdoor allergens are responsible, the condition may be referred to as hay fever or seasonal allergies. Only your doctor can diagnose seasonal allergies or pinpoint your triggers. But if you identify with any or all of the common seasonal allergy patterns below, it could be an indication that further evaluation is in order.
- If you suffer more in the springtime, tree pollen may be your trouble.
- If you sniffle more during the summer months, you may be allergic to grass and weed pollens.
- If your symptoms flare up in late summer and fall, weed pollen or mold spores5 could be the culprit.
- If you exhibit symptoms all year long, you may be allergic to indoor irritants such as dust mites and molds.6
Despite their designation as "seasonal" allergies, it's worth noting that pollens and conditions vary widely with locale. In fact, pollination may occur year round in parts of the southern United States, making seasonal allergies a year-round concern.7
1American Academy of Allergy, Asthma and Immunology. The Allergy Report Volume 1: Overview of Allergic Diseases: Diagnosis, Management, and Barriers to Care. Available at http://www.aaaai.org/ar/working_vol1/009.asp. Accessed February 15, 2008.
2Definition of Atopy; Definition of IgE. Available at http://www.medterms.com/script/main/art.asp?articlekey=31081 and http://www.medterms.com/script/main/art.asp?articlekey=21070. Accessed March 21, 2008.
3Hay Fever. MayoClinic.com. Available at http://www.mayoclinic.com/health/hayfever/DS00174/DSECTION=1. Accessed March 17, 2009.
4Airborne Allergens. PATADAY™ Web site. Available at http://www.pataday.com/airborne-allergens/Airborne-Allergies.asp. Accessed March 24, 2008.
5American Academy of Allergy, Asthma and Immunology. The Allergy Report Volume 1: Overview of Allergic Diseases: Diagnosis, Management, and Barriers to Care. Available at http://www.aaaai.org/ar/working_vol1/009.asp. Accessed February 15, 2008.
6American Academy of Allergy, Asthma and Immunology. Allergic Rhinitis Patient Fact Sheet. Available at http://www.aaaai.org/patients/resources/easy_reader/rhinitis.pdf. Accessed March 21, 2008.
7American Academy of Allergy, Asthma and Immunology. The Allergy Report Volume 1: Overview of Allergic Diseases: Diagnosis, Management, and Barriers to Care. Available at http://www.aaaai.org/ar/working_vol1/009.asp. Accessed February 15, 2008.
