For many people, a food allergy is an obvious and dangerous thing. Within minutes to hours of eating a food, their throat will swell, they’ll have itching, trouble breathing, or even go into shock. While these people are the most endangered by food allergies, they’re also the most likely to be treated efficiently. For others, a reaction may be less severe and difficult to diagnose.

If your reaction to foods is more minor, keeping a food journal is the best way to pinpoint your symptoms and what specific foods are causing them. You don’t need a special journal – any notebook will do, but a calendar or day planner might work better. Every day, write down everything you eat and when you eat it. Also write down any symptoms you might be having and when they occur. You can look at this yourself, or with your doctor, and determine what foods might be triggering your reactions.

Not all issues with food are actually allergies. Food allergies occur when your body mistakes a harmless substance as being dangerous and alerts the immune system to react. Because there is nothing your body can counteract (no dangerous substance), this extra response can actually cause severe problems. Symptoms like hives, other rash, itching, facial swelling, headache, stomachache, runny nose, and difficulty breathing are all signs of a true allergic reaction. This is why it’s important to keep track of all your symptoms so your doctor will know if you are experiencing a reaction or simply having digestive issues.

If you have stomach or other abdominal pain when you eat a certain food, but don’t have other allergic symptoms, you may just have digestive problems rather than an allergy. This is generally treated simply by waiting and then avoidance rather than administering medication as you would with a real allergic reaction. Even if you don’t think it is an allergic reaction, it is still worth seeing a doctor because your symptoms could be caused by a severe digestive disorder.

If you think you have a food allergy, don’t avoid going to the doctor. While it seems simple enough to avoid the foods that make you sick, sometimes that can be fairly difficult. Some foods can trigger reactions in miniscule amounts, or they may be labeled under a different name on ingredients lists. Or, you could be totally wrong about what is causing your symptoms. Only your doctor can sort it out.

If your doctor reviews your food journal and feels you may have a food allergy, they will run skin prick tests and various blood tests to determine which allergen specifically is triggering your reaction. From there, they will likely recommend avoiding the food and a possible course of treatment. They may also prescribe an allergy kit with emergency medicine in case of accidental exposure.