So I have a sinus infection got proscribed augmenton and tessalon but idk if I'm allergic to either how long after I take will I know?

Can't tell. If you had never taken augmentin (its ingredients) or penicillin before, it will take 10 or more days for you to become allergic (if you do become allergic). If you have had the drug before, reactions may develop(if at all) in minutes or days depending on the type of allergic reaction. Have not encountered allergy to tessalon but people with red meat allergy may have problem with gelatin cap.