I have a horrible allergy to cats so I take a lot of medication to be able to be around my cats.
Cat allergy in humans is an allergic reaction
Why do some humans have allergic reactions to cats but other humans dont
The most common of these allergens are the glycoprotein Fel d 1, secreted by the cat's sebaceous glands and Fel d 4, 
I'll have to take your word for it, I have no idea what any of that means.
An allergic reaction is a histamine reaction that is usually characterized by coughing, wheezing, chest tightening, itching, nasal congestion
Does it affect the immune system?
Those with severe, life-threatening cat allergies face tremendous challenges due to lack of public awareness about anaphylactic cat allergies