How can i treat a fungal sinus infection?

Need a doctor: Your question is too complex for answer here, and the answer depends on many details that we don't have. You should see your doctor, or an ENT surgeon, or an infectious disease specialist.

Depends: Most fungal sinus disease is treated surgically with functinal endoscopic sinus surgery to open the sinus ostia and completely clear out all of the sinus disease. Rarely anti fungal mediations are necessary or required in most cases. Also in most cases irrigation daily and treatment of allergies are necessary to prevent it from returning. You need to see a rhinologist, specialized ent.