To know if one is allergic to cats, look for symptoms such as sneezing, runny or stuffy nose, coughing, wheezing, chest tightness, itchy or watery red eyes, skin rash or hives—often appearing within minutes of exposure to cats or their environment. The most reliable way to confirm a cat allergy is through medical testing, such as a skin-prick test where small amounts of cat allergen extract are placed on the skin, or a blood test that checks for specific allergy- causing antibodies. Monitoring if symptoms improve when avoiding cats can also be indicative but professional diagnosis is recommended for certainty and appropriate treatment planning.