I have an allergy, i am living with 7 yrs old cat! the dr advised me to move the cat away from home but i can't ! does it have any negative effect ?

Unfortunately yes: Cat lovers have a real problem when they develop allergies, even if u aren't now allergic to cat dander u can develop such allergy later on continued exposure, some environmental measures as frequent vacuuming and washing the cat with anti dandruff shampoo might help, ultimately immunotherapy would be helpful, but such decision is judgmental, ur allergist would be the right person to ask.