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