Many people are extremely allergic to cats so far as going into Anaphylactic Shock -
After exposure to shed cat dander, a severe allergic response causes sudden release of chemicals and histamines from its blood cells. These chemicals cause rapid blood vessel swelling. Fluid leaks from the blood vessels into surrounding tissues, starving organs of vital oxygen and blood flow; the body's vital functions shut down. The sufferer can become cold and clammy, faint, nauseous, drowsy, confused, and may develop a raised, blotchy rash ("hives"), and swelling of the tongue and lips. Some people who suffer allergy collapse and the heart can stop beating; anaphylactic shock can kill if cat dander response is severe enough.
http://www.ehow.com/about_6589623_cat-dander-causes-anaphylactic-shock.html
Which is why many public places do not allow cats. I love cats but my wife is allergic and cannot be near a cat without having her eyes swell shut. Once a cat has been in a room it is almost impossible to remove the danger.
