question: hi my dentist gave me cephalexin 500mg for tooth infection ,though I think its a sinus infection, : stuff nose face swelling , teeth pain and swelling , sensitive to hot more than cold . it started out 5 days ago , it started with teeth pain and clear liquid driping from nose . I called dentist ,though no one was open due to the holidays so I found one that gave me a prescription from the details I gave him. I did not take it until I got back in my home town when I saw the dentist and he said I should take the antibiotic  until I can see a specialist. I don't want to pay lots of money if its a sinus problem and not tooth infection. it is the #2 right upper tooth and the one next to it is sensitive as well. what is you opinion and advise? can this antibiotic help?