I had two sinus surgeries as a child, and used to get at least two serious sinus infections a year. These sometimes required a couple rounds of antibiotics, sometimes combined with steroids. I was supposed to have sinus surgery back in August and skipped it...since starting a Paleo diet in October, I have not had a single sinus infection or even a cold! I noticed the biggest improvement after I spent a weekend baking for a bridal shower and eating a LOT of non-Paleo, gluten-containing treats. After about two days of reverting to that SAD diet, my congestion started to return hardcore. I hopped back on the Paleo bandwagon, and it was gone shortly. As Kecia Lynn said, I think gluten may have had the largest effect for me.