A smelly, mucous or a discharge or a foul smell from the nose can be of 2 types, one is he is feeling the smelly discharge, his sense of smell is proper and he can feel the bad odour that is emanating from his nose or it is a bad smell that is perceived by others but the person himself does not know it. That is seen in a condition called as atrophic rhinitis. Although it is still not common, it is seen nowadays and there is increased amount of antibiotics, extensive surgery that has been done in the nose. That can lead to atrophic rhinitis.so many other causes can cause discharge which is very smelly from the nose. In adults and kids the causes are different. In kids it is because of a crust which has been developed in one side or both the sides of the nose which has not been cleaned properly or it can rarely be a foreign body which we see in our practice, where we have a unilateral, that mans from one side of the nose which may or may not be bloody but it is very offensive but in adults the smelly discharge can be due to a condition called as atrophic rhinitis, also infected sinuses. You have acute bacterial or viral sinusitis or fungal sinusitis, which can cause this discharge from the nose which can be very offensive. In any case, you have any offensive discharge it is imperative that you see your ENT doctor as soon as possible.