Other than food, different factors in the environment can trigger many types of allergic reactions. From dust mite to dry cleaning fluids, pollution to pollen, the environment can be hazardous to those sensitive to certain factors.
If your hay fever or sinusitis occurs at the same time of year, every year, it is likely that you are allergic to pollen or other plant matter that is present in the air during that season. Post-nasal drip and headache may also indicate that you are inhaling a substance to which you are allergic.
Contact allergies normally take the form of skin conditions, such as dermatitis, which occur on the area of the skin that has been exposed to the allergen. If you are exposed to chemicals during the course of your work, you may develop a contact allergen. This is very common amongst hairdressers, dishwashers and those working with industrial chemicals. Protective clothing such as gloves should be used whenever possible.
Once you have an idea of which foods you are allergic to, avoid them strictly for a period of two weeks and continue to record your symptoms. After this time, challenge your body by eating a small portion of the food, and observe whether the symptoms return or worsen.
Many people find that after the re-introduction of the food, their symptoms are stronger than they were before.