If you have tried this to no avail you may want to try an elimination diet where you remove one food from your diet for 1 week then reintroduce it to check for reactions. The most common allergens include wheat, oranges, tea, coffee, soybeans, corn, sugar and food additives. It is also important to remove as many refined foods from your diet as possible, particularly those containing hydrogenised and partially hydrogenated fats. These fats cause prostaglandin release in the body and an exacerbation of inflammation, histamine release and allergy or sinus symptoms. Fresh fruit, vegetables, beans, nuts, seeds and grains are your best medicine.
Herbs are an important line of defence.
I use several herbs that are specific for upper respiratory catarrh. You can make up a blend of dried or fresh herbs and make a tea or purchase or make up a concentrated liquid mixture called a tincture. The herbs can also be taken in tablet or capsule form. You can use a traditional nose drop preparation consisting of cold pressed sesame oil . This is very effective for sinus problems.