Could teeth clenching and grinding be causing sinus pain and inflammation? doctors have ruled out allergies and infection.

Not inflammation: Teeth grinding can lead to jaw pain and headache, but not chronic inflammation. Chronic irritation from dust or airborne irritants (chemical or otherwise) can lead to swelling. See an otolaryngolist, allergist, or good general internist and keep plugging away. Some of these things need another look to rethink the problem to get to a solution.

Some: Clenching or grinding called bruxing can lead to pain that appears to be coming from the sinuses. Other symptoms for nighttime bruxing include the pain being worse in the morning. I would suggest seeing a dentist who can diagnose and treat your symptoms. If your dentist can't look for a dentist at www.Aaop.Org or www.Aacfp.Org.