An allergy is your immune system's overreaction to certain substances, even though those substances are harmless. These substances, or allergens, trigger your body to release immunoglobulin E, which is an antibody. This in turn tells your mast cells and basophils to attack the invading allergen with chemicals, including histamine. If you're allergic to cats, the allergen is most likely the animal's dander, or shed skin flakes, or the proteins in its saliva and urine. Since cats lick themselves more often than dogs and the protein in their saliva is miniscule, cat allergies are twice as common as dog allergies. The symptoms can involve coughing, wheezing, hives, itchy eyes, sneezing and a runny, itchy or stuffy nose.
There is no cure yet for cat allergies. They normally develop by the time you're 10 years old, they peak in your 20s, and by the time you're 60, they should pretty much be gone. But it's understandable if you don't want to wait for them to go away in order to feel "normal." That's why there are treatments to help alleviate the symptoms of cat allergies. Common recommendations include antihistamines, decongestants and sometimes prescription steroids. Some people try allergy shots, or immunotherapy. Allergy shots require patience, as the cycle can take a year to complete. Even then, they're not guaranteed to be effective. Also, allergy shots aren't safe for children younger than five years of age. However, some studies have shown that by exposing kids to pets when they're young you reduce their risk of developing allergies.
While some of these treatments may work to effectively relieve cat allergy symptoms, most doctors recommend avoidance as the best measure. If you have allergies, you're better off not having a cat in the house. If you plan to stay in a house where there are cats, ask the owners to keep the room you'll stay in cat-free for a few weeks before you get there.