What's the most effective drug for the treatment of alergia?

The treatment would depend upon the kind of allergy that one has, treatments for allergies include allergen avoidance, use of anti-histamines, steroids or other oral medications, immunotherapy to desensitize the response to allergen, and targeted therapy.

For better results please do talk to your doc/pharmacist.

My Mom developed sneezing and some other symptoms I had an antihistamine type drug here at home just a few tablets, I checked with the doctor's office and found out it was safe to give her, it helped but not enough, a short time later I was in the pharmacy where she gets her medication the pharmacist came from behind the counter and explained what would help what then went back behind the counter and looked at her medications he mad a suggestion and it worked better than the one she had taken in the first place. so either talk with the doctor, or ask you regular pharmacist who is familiar with you and your medications. and the pharmacist suggested I purchase a small amount (they had like 5 on display) enough to let me know how it worked and was also cost effective. take good care