Allergies are the result of a misguided immune system. Even though some substances are perfectly safe, if your body is overly sensitive, it may misidentify certain allergens as dangerous and react by fighting them off. The most common allergens produced by cats are the proteins found in the cat's saliva and sebaceous glands, along with the dander, or skin flakes, that they shed.

The battle against allergens can be manifested in a number of ways. Most often, people with cat allergies suffer from cold-like symptoms. If the allergen ends up on eye or nose membranes, the reaction is likely to be puffy or red eyes, congestion, or itchy eyes and nose. Inhaling the allergens can cause coughing, wheezing or sneezing. A scratch, bite or lick from a cat might cause the skin to turn red on the site of contact. People who are highly sensitive to cats can develop hives or a rash on their face, neck or upper chest when they're exposed to allergens. Those with asthma have a higher chance of asthma attack when they come in contact with cat allergens. Allergic symptoms can take a few minutes to develop when you come into contact with a cat, but it can also take a few hours, depending on your level of sensitivity.

To determine whether you suffer from cat allergies, observing symptoms isn't usually enough. Other allergens can result in the same symptoms. An allergist can perform a skin or blood test to determine whether you have cat allergies, but such tests aren't completely reliable. One way to test your diagnosis is to stay away from cats for at least a few months to see if your symptoms subside. If the cat was in your house prior to your trial separation, make sure to do a thorough cleaning after the pet is gone. It can take months before the house is allergen-free.