Non itchy rash flare up 3 times in 24 hours despite antihistamines. Is there a chance that I m allergic to my cat? (9 months old). No prior symptoms.

Rash not cat allergy. If it doesn't itch it's not an allergic rash. The other possibility is that the antihistamines are strong enough to suppress itching but not the rash. Try stopping the antihistamine. If the rash continues to appear and becomes itchy, then yes, it could be the cat. You will want to see a health care professional at that point.