Should I track my allergies by keeping a food diary?

If you think you may have a food allergy, a food diary is an important tool to help you figure out exactly what you're reacting to. There's more to keeping a food diary than just writing down what you eat, so here's a look at how to keep a food diary and what it should look like.

A food diary needs to identify not just what you ate, but the time you ate it, how you felt after eating, whether you had any reactions, and the time of any reactions you might have experienced, as well as any medications you took. If you have a food allergy, a pattern will emerge over time to show correlations between ingestion of a particular food and a reaction you've documented in your diary.

Your food diary should cover at least a month, to make sure there is enough data to draw accurate conclusions.

Interpreting a food diary can be tricky, since we tend to eat multiple ingredients mixed together, so it's hard to be sure which ingredient caused a reaction. For this reason, it's recommended to use a smartphone app rather than keeping a paper diary, if at all possible.

Certain apps will do the tracking for you and analyze your data to tell you what's most likely to be causing your reactions. You can then take this information to your doctor, who can use it to decide which allergies you need patch tests for. If you don't have a smartphone, your doctor can help you analyze your paper diary.

If you experience an immediate and severe reaction such as anaphylaxis, you must seek urgent medical attention, as this is a life threatening condition. Obviously, any further exposure to the food you think caused the anaphylaxis should be avoided.

However, most allergic reactions are not as severe as this. If you experience a mild reaction such as a skin rash, it pays not to cut out the food you suspect is causing the reaction right away. Your food diary will need data from multiple exposures to supply accurate conclusions. Keep your diet the same for the period of your food diary, before removing the foods the diary identifies as your allergens.

After you've kept your food diary for a month, you can either see your doctor to get patch tests for your suspected allergens, or go at it alone by eliminating those allergens identified by the diary one at a time, documenting how you feel without them in your diet. If later reintroduction of a food you've previously eliminated causes symptoms to return, you have pinpointed an allergen or intolerance.