Understanding Region-Specific Allergens for Dogs and Cats

Many of our canine and feline patients have pollen-related issues, ranging from mild pruritus to significant dermatologic problems. Environmental components often trigger these reactions, but allergens aren't consistent regionally.1 Geographic location plays a significant role in identifying what irritants a pet is exposed to. Understanding region-specific allergy triggers is necessary for accurate diagnosis and effective treatment in addition to evaluating lifestyle, seasonal or non-seasonal history, and the patient's clinical signs. All these factors must be considered in order to prioritize the relevant allergic triggers and help direct an effective treatment.

Pollen, mold, dust mites, and weeds are the most common environmental causes of allergies in pets.2 However, the specific trigger can vary widely depending on the region, time of the year, and the patient's personal immune response. For example, pets in California may have an allergic reaction to certain trees, such as black walnut or eucalyptus, while those in Florida may be triggered by Australian pine or bald cypress trees. Other regional irritants include molds, grasses, insects, dust mites, weeds, and dander from other animals.

  Learn more about what regional allergen panels are available with IDEXX Reference Laboratories.

Region-Specific Pet Allergens

Some allergens are common in all parts of North America, but many are specific to a certain region. Regional environmental substances include:

  • Molds and fungi: Molds and fungi most commonly affect pets living in regions with high humidity and dampness, which promote their growth. For example, Aspergillus is especially prevalent in damp, humid climates such as the southeastern United States, while Cladosporium is more common in cooler, wetter regions such as the Pacific Northwest.3,4

  • Grasses: A region's climate, soil type, and growing conditions determine which grass species thrive there. Bermuda grass flourishes in warm, sunny climates and is a frequent problem for pets living in states such as Florida, Georgia, Alabama, and parts of Texas.5 Sweet vernal grass is more commonly found in moist, temperate climates with adequate rainfall and is more problematic for pets in the Northeast and Great Lakes regions.6

  • Insects: Differences in climate, habitat, and local ecosystem influence which insects populate a given region. While fleas are found nationwide, these parasites are most problematic for pets in the southern U.S., coastal regions, and areas with mild winters.7 Cockroaches are also prevalent throughout the country but tend to be more pervasive in urban areas and warmer climates, including the southern U.S. and major cities.8

  • Mites: Some mites thrive indoors, while others are more prominently found outdoors, depending on factors such as humidity, temperature, and vegetation. Dust mites are most prevalent in humid climates, such as the Southeast and Gulf Coast, but house dust mites can be found indoors nationwide.9,10 Storage mites can also be found in all regions, but are most problematic in areas with fluctuating humidity levels, such as the Midwest and Pacific Northwest.11

  • Trees: Hickory tree pollen, which is highly allergenic, is most common in cooler climates such as the Northeast and Midwest.12 Olive trees are more problematic for pets in the Midwest and Southern states.13

  • Weeds: Dog fennel thrives in warm, humid climates and is a common trigger for pets living in states such as Florida, Georgia, and Alabama.14 Scale is a significant allergen in California, Nevada, Utah and Wyoming.

Veterinarians should also consider seasonality when identifying a pet's triggering allergens. Many categories, such as tree pollen, grasses, and weeds, are more prevalent during specific times of the year.

Diagnosing Region-Specific Skin Allergies in Dogs and Cats

The diagnosis of atopic dermatitis is really a diagnosis of "rule-out". When a patient presents with allergy symptoms, such as itchy skin, erythema, hot spots, and recurrent skin and ear infections, a detailed history is critical to determine the onset time, environmental exposure, seasonality, and prior treatments. Other causes, such as flea allergies, infections, and other dermatoses are first ruled out using diagnostic testing, including skin scrapings, cytology, elimination diets, and therapeutic trials. Once these are eliminated as a cause of clinical signs and a diagnosis of atopic dermatitis is made, intradermal skin testing and serum allergy testing can help pinpoint specific allergens, particularly region-specific triggers relevant to the pet's environment.

Immunotherapy for Regional Allergies in Dogs and Cats

Once the patient's relevant environmental allergens are identified through allergy testing, allergen-specific immunotherapy (ASIT) can be initiated with an ultimate goal to reduce their symptoms. Currently, immunotherapy is the only available atopic dermatitis treatment that has the potential to change the disease's long-term course and prevent dependency on medications such as corticosteroids and antihistamines, which can cause unwanted side effects. Immunotherapy administration options include:15

  • Injectable formulation: Subcutaneous administration is widely used to deliver small, controlled doses of specific substances, gradually increasing the dose, to modulate the immune response and induce an eventual state of tolerance.

  • Sublingual formulation: Administering drops under the tongue is an option for pets who may not tolerate injections.

Many veterinary dermatologists recommend testing patients late in the allergy season, and if possible, within one month after seasonal allergies in dogs and cats decrease.16 The goal is to test the pet after they are exposed to every allergen for that season.

Immunotherapy's efficacy relies heavily on including substances relevant to the pet's location. For example, a dog in the Midwest may require treatment for corn pollen, hickory, and sage mix, while a cat in the Pacific Northwest may need treatment for nettle and Russian thistle. Early intervention is also important when treating atopy in pets, and immunotherapy should be started as soon as possible after diagnosis to alleviate the pet's clinical signs and reduce the risk of secondary infections and chronic inflammation.15

Geographic factors play a significant role in a pet's allergy profile, and understanding these regional differences is important when diagnosing environmental allergies. Addressing regional triggers is a necessary step in improving allergy management and can help veterinarians provide long-term relief and significantly improve their patient's quality of life.

References

  1. Newson, R.B., et al. (2014). "Geographical variation in the prevalence of sensitization to common aeroallergens in adults: the GA(2) LEN survey." Allergy, 69(5), 643-651. https://onlinelibrary.wiley.com/doi/10.1111/all.12397

  2. Burke, J. (2022). "The nuts and bolts of canine atopic dermatitis." dvm360. https://www.dvm360.com/view/the-nuts-and-bolts-of-canine-atopic-dermatitis

  3. Bonner, J.T. (2018). "A study of the temperature and humidity requirements of Aspergillus niger. Mycologia, 40(6), 728-738. https://www.tandfonline.com/doi/abs/10.1080/00275514.1948.12017741#:~:text=The%20combined%20temperature%20and%20relative,is%20near%2030%C2%B0%20C.

  4. Pacific Northwest Pest Management Handbooks. "Seed crop, crucifers (Brassica, Erusa and Raphanus spp.)—Cladosporium leaf spot." Oregon State University. Retrieved February 1, 2025 https://pnwhandbooks.org/plantdisease/host-disease/seed-crop-crucifers-brassica-eruca-raphanus-spp-cladosporium-leaf-spot

  5. Ghobrial, G.M., et. al. (2002). "Identification and characterization of the allergenic proteins of Bahia grass (Paspalum notatum) pollen. International Archives of Allergy and Immunology, 128(4), 304-309. https://karger.com/iaa/article-abstract/128/4/304/164604/Identification-and-Characterization-of-the?redirectedFrom=fulltext&utm

  6. NatureServe. Anthoxanthum odoratum. NatureServe Explorer. Retrieved February 1, 2025 https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.160120/Anthoxanthum_odoratum

  7. Koch, S. (2015). "Flea prevalence in dogs and cats." Today's Veterinary Practice. https://todaysveterinarypractice.com/infectious-disease/flea-prevalence-in-dogs-cats

  8. Chew, G. L. (2012). "Assessment of environmental cockroach allergen exposure. Current Allergy and Asthma Reports, 12(5), 456-464. https://link.springer.com/article/10.1007/s11882-012-0287-y

  9. Fernandez-Caldas, E., et. al. (1990). "House dust mite allergy in Florida: Mite survey in households of mite-sensitive individuals in Tampa, Florida. Allergy Proceedings, 11(5), 263-267. https://health.usf.edu/-/media/v3/usf-health/medicine/Internal-Medicine/allergy-and-immunology/newsletters/2021/2021-Newsletter-052.ashx

  10. Arbes, S. J., et. al. (2003). "House dust mite allergen in U.S. beds: Results from the first National Survey of Lead and Allergens in Housing." Journal of Allergy and Clinical Immunology, 111(2), 408-414. https://www.jacionline.org/article/S0091-6749%2802%2991278-9/fulltext

  11. Jena, M. K., et. al. (2024). "The impact of humidity on the functional response of Blattisocius Mali (Acari: Blattisociidae) preying on the acarid mite Tyrophagus putrescentiae." Scientific Reports 14. Article number: 28051. https://www.nature.com/articles/s41598-024-78997-w

  12. IQVIA. "Birch (Betula) genus level details and allergy info." Pollen.com. Retrieved February 1, 2025 https://www.pollen.com/research/genus/betula

  13. Shah, M. (2025)."Facts, prevention, and relief for elm tree allergies for 2025." Wyndly. https://www.wyndly.com/blogs/allergens/elm-tree?srsltid=AfmBOoqFgsy1269F5nABNjM89QrIxCjkkMnRJIdu-kPy5efYwU23ZoLl

  14. Van Deelen, T. R. (1991). Eupatorium capillilifolium. In Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. https://www.fs.usda.gov/database/feis/plants/forb/eupcap/all.html

  15. Brooks, W. (Revised 2023). "Immunotherapy for allergies in dogs and cats." Veterinary Information Network. https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952556

  16. Texas A&M Veterinary Medical Teaching Hospital. "Allergies," Retrieved February 1, 2025 https://vethospital.tamu.edu/small-animal/dermatology/allergies/

Angela Beal
DVM

Angela Beal is a veterinarian in Columbus, Ohio who loves using her writing to help veterinarians live more fulfilling lives by helping make practice life more efficient and less stressful. Angela has a background in private practice and academia, and since 2020, she has worked full-time with Rumpus Writing and Editing, a veterinary-specific writing and editing company. Rumpus’ clients include veterinary practices and industry partners, including marketing companies, national corporations, consultants, and several international businesses. Learn more at rumpuswriting.com. The views and opinions in this piece are the author's own and do not necessarily reflect the views of either The Vetiverse or IDEXX.


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