You notice that you develop a mild headache soon after you eat. Sometimes it's accompanied by an upset stomach. These can be signs of a food allergy. A visit to an allergy physician will narrow down the problem foods so you can avoid them and find substitutes. Here is what you need to know about food allergies and how to stop those annoying headaches.

A Small Group of Foods Cause People Big Problems

Most food allergies are due to just a few types of foods, which include:

• Dairy products
• Eggs
• Fish and shellfish
• Wheat
• Soy beans
• Groundnuts, such as peanuts
• Tree nuts, such as almonds

If you're allergic to one of these foods, then you'll also have a reaction to products containing those foods. This can be a challenge because the use of specific foods may not be listed in an ingredients label. For example, peanuts are used as a thickener for sauces but may not appear on a restaurant menu with the entree.

You may also have a reaction to some form of these foods but not another. People who are allergic to a specific protein in cow's milk may not have a reaction to the protein in goat's milk.

Testing for Food Allergies

An allergist uses two tests to determine which foods you have a reaction to. Each test gives a little different information, so both may be done to help your doctor with the diagnosis.

Skin test - This test is done by placing a drop of liquid containing a specific food on your skin. The skin is then pricked under the liquid drop. If you have a reaction, it will occur in just a few minutes. The reaction can be a small reddened area on the skin or a rash that begins to itch. This is an easy test to do and your doctor can test for several food allergies at once.

Blood test - Your blood can be tested for the presence of an antigen released by your immune system in response to a specific food. The presence of the antigen indicates that you've been exposed to a food allergen, but the test won't help your doctor to know which food. If you have a skin condition that prevents the use of the skin test, then the blood test is the only alternative.

Your doctor may have you do a challenge test next. This will narrow down the results to a specific food. To do this test, the doctor will have you eat a very small portion of a food that they suspect causes you to have a reaction. You'll increase the amount of the food you consume over a number of days until you begin to have symptoms. This tells you which foods you have a reaction to and how much you have to eat to have symptoms.

Treating Food Allergies

Food allergies cannot be cured, but knowing which foods you react to helps you limit them in your diet or avoid them altogether. This is where the challenge test is helpful. You may discover that while you have a dairy allergy, you can eat small portions of cheese without a problem.

You can also try substituting foods for something to which you won't have a reaction. For example:

• If you're allergic to eggs, it may be the protein in the yolk that causes the problems so you can try eating just the egg white.
• If you're allergic to wheat, it's likely the gluten is the problem, so you can try a gluten-free flour or other flours such as almond or rice.

Once you know the precise foods you're allergic to, you can adjust your diet to get rid of those headaches and enjoy eating again.