My wife wants me to tell the doctor about this, but I am afraid it sounds crazy even to me. I know I have seasonal allergies, but I don't know what this is. I smell a flat, dirty, almost musty smell in my head. It comes and goes, but when I have it is strong and it almost chokes me. If I place something over my nostrils to "filter" the smell I don't smell it as bad, but it is almost like when you have a bad cold and when you smell certain smells it about gags you. What can this be?