I used to suffer from excrutiating sinusitis. I cut down on dairy foods .Use soya milk in cereals, mild cheese, and butter as a treat now and then. I use mayo in sandwiches. Semi-skimmed milk in coffee - limited. Delighted to say my sinuses cleared within a month and have now gone for over 2 years without a head cold. As I am in what my doctor calls the critical stage of COPD this has made a big difference to helping me cope. I am new to this site but hope this is helpful.