I have frequent sinus infections with a history of nasal polyps. it seems as if dairy worsens my sinuses. is this common? does this mean i'm allergic to dairy? should i have food allergy tests completed?

Possibly: Yes, you could have a food allergy, but dairy products as increase mucous production as well as making the mucous thicker. With the addition of a polyp, the sinuses have a hard time draining thicker mucous and block the sinuses and trap bacteria. The mucous is thickened for sugar molecules and is a great food sorce for the trapped bacteria, leading to an infection.

Not necessarily: Many people report increased mucus quantity or thickness when drinking milk. This is not due to an allergy. Milk allergy rarely present with isolated nasal/sinus congestion. If fatty milk is triggering reflux, it can indirectly increase congestion. If you are concerned, i recommend testing, but don't be surprised if the testing is negative.