Is it alright to take antihistamines for allergy problem?

I am a 48 years old male. I get sneezing, uncontrolled for no good reason. I tried to get immunised and consulted immunologist for the allergy test. After 4 sittings also, allergy was not detected. However, I feel relief after taking any anti-histamine tablet. How long should I take this? Is there any side effect? I had stroke last year. Ramistar, Preva and Triptomer tablets have been continued for me. Does the anti-histamine tablet have any effect on these medicine or does this allergy disease has any relation with my recent ailment?