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MAY 2006
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Learn More
In Learn More the National Geographic magazine team shares some of its best sources and other information to expand your knowledge of our featured subjects. Special thanks to the Research Division.

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Did You Know?Did You Know?

Humans are not alone when it comes to enduring the misery of allergies. All sorts of pets, including rabbits, birds, hamsters, and (most commonly) cats and dogs, suffer from allergies as well. Allergic reactions in pets and humans are caused by the same antibody in the immune system, which overreacts to a substance that is normally harmless. Although pets have been known to cough, wheeze, and sneeze when they encounter certain allergens, they suffer mostly from allergic dermatitis, which causes them to itch. To satisfy the itch, they end up scratching all over and chewing and biting their limbs, resulting in scabs, hair loss, and skin infections.

Cats and dogs can have allergic reactions to a variety of substances including fleas, food, plastic, pollen, mold, and dust mites. Flea allergies are the most common and are triggered by the proteins in flea saliva, which cause the animal to experience extreme itching and irritation, which can last for days from one single bite. Food allergies are also common for pets. In cats and dogs, allergic reactions most often come from eating beef and dairy. Besides itching, animals can also have diarrhea and vomiting from eating a substance they are allergic to. Pets can develop seasonal and environmental allergies that cause them to itch severely from inhaling pollen, mold, or other substances. Though it's less common, pets can also become allergic to plastic and can develop irritated skin on or around the nose from using a plastic food or water dish.

If your pet is suffering from an allergy, the hardest part is figuring out just what is causing the reaction. One way of finding the cause is with a skin test, in which different substances are injected into the skin to see if one in particular produces a reaction. With food allergies, veterinarians recommend a hypoallergenic or restricted diet for up to ten weeks, during which different foods are introduced weekly to determine the culprit.

Unfortunately, as with humans, there is no known cure for allergies besides avoidance. Solutions for fleas can be found in various products such as shampoos and repellents. Sometimes steroids can help make the animal more comfortable, and there are lotions and pills that can aid in reducing the severity of itching. There is also a desensitization process through allergy shots that works much in the same way as for humans—by injecting a little of the allergen weekly until the animal becomes used to it. This process sometimes helps, but it can take months before any improvement is seen.

—Emily MacDowell

Related Links

American Academy of Allergy, Asthma & Immunology
View a mega allergy and asthma site with information tailored for patients and professionals alike. Access fact sheets on all types of allergies, search for an allergist in your area, and read the latest research in the Journal of Allergy and Clinical Immunology.

Food Allergy and Anaphylaxis Network
Learn the difference between food allergies and intolerances and how to diagnose and manage common food allergies.

Indoor Air Quality
Discover how to better control the triggers of allergies and asthma such as mold and dust mites with guides from the U.S. Environmental Protection Agency.

American Partnership for Eosinophilic Disorders
People with eosinophilic disorders, such as Evan Green (see page 134 in the print article), have too many eosinophils—a type of white blood cell—in their digestive system. The result is a disabling condition that requires life-long restricted diets. Learn more about these disorders and their connection with food allergies.

Allergy and Asthma Network/Mothers of Asthmatics
Get answers on how to manage allergies and asthma at home, school, and work with discussions ranging from children carrying their inhalers to school to travel tips to facts and myths about pet allergies.


The Allergy Report. American Academy of Allergy, Asthma & Immunology, 2000. Available online at www.theallergyreport.org.

Blumenthal, Malcolm. "The Role of Genetics in the Development of Asthma and Atopy." Current Opinion in Allergy and Clinical Immunology (April 2005), 141-5.

Creticos, Peter, Yi-Hsing Chen, and John Schroeder. "New Approaches in Immunotherapy: Allergen Vaccination with Immunostimulatory DNA." Immunology and Allergy Clinics of North America (Vol. 24, 2004), 569-81.

Global Burden of Asthma. Global Initiative for Asthma, 2004. Available online at www.ginasthma.org.

Leung, Donald, and others. "New Insights into Atopic Dermatitis." Journal of Clinical Investigation (Vol. 113, 2004), 651-7. Available online at www.jci.org/cgi/reprint/113/5/651.

Liu, Andrew, and James Murphy. "Hygiene Hypothesis: Fact or Fiction?" Journal of Allergy and Clinical Immunology (Vol. 111, 2003), 471-8. Available online at www.jacionline.org.

Understanding the Immune System: How It Works. U.S. Department of Health and Human Services, September 2003. Available online at www.niaid.nih.gov/Publications/immune/the_immune_system.pdf.

Waltraud, Eder, and Erika von Mutius. "Hygiene Hypothesis and Endotoxin: What Is the Evidence?" Current Opinion in Allergy and Clinical Immunology (Vol. 4, 2004), 113-7.

Yazdanbakhsh, Maria, Peter Kremsner, and Ronald van Ree. "Allergy, Parasites, and the Hygiene Hypothesis." Science (April 19, 2002), 490-94. Available online at www.sciencemag.org.

NGS Resources

"Allergy Alert!" National Geographic World (June 1986), 14-17.

Newman, Cathy. "Pollen: Breath of Life and Sneezes." National Geographic (October 1984), 490-521.
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