I smell a mildew smell the first breathe i take after i sneeze. why is that?

Fungal sinusitis: That's an unusual symptom. You might have fungal sinusitis... Not a bid deal... Very common in south east us.. But very common. It may also be nothing... Best to be seen by an ENT and have a ct scan of sinuses based on exam.

Allergy vs infection: If you are allergic to mold (a common allergy), when you encounter this in the air, it may make you sneeze. You may then notice the smell. Sometimes a sinus infection can give you a foul smell. If you have symptoms of facial pain/pressure, discolored drainage, see your doctor for treatment.