My clydesdale has developed some disgusting creamy snot out of one nostril which stinks to high heaven! The vet is unsure whether its his teeth or horse sinusitus. She can't see anything wrong with his teeth but if it was a hairline crack that got infected or something she would not be able to see. Has anyone experienced this and if so what happened? She has given him antibiotics... how soon are these supposed to work?...she said not to worry unless it was still bad in a week but of course I am worrying!!! Its been 2 days and the smell is not as bad but he is still gushing snot!!!