Understanding the Difference — A Patient Teaching Guide
Many people experience reactions to food, but it's important to understand whether you have a food allergy or a food intolerance. While they may seem similar, they are very different conditions with different causes, symptoms, and treatments.
Food allergy symptoms typically appear within minutes to two hours after eating the offending food.
Some people experience a severe, life-threatening allergic reaction called anaphylaxis. This requires immediate emergency treatment.
Signs of Anaphylaxis:
If you experience these symptoms, CALL 911 immediately and use your epinephrine auto-injector if prescribed.
Food intolerance symptoms are usually less severe than allergy symptoms and typically affect only the digestive system. Symptoms may take several hours to appear after eating.
Inability to digest lactose (milk sugar) caused by lack of the enzyme lactase. Very common in adults.
Difficulty digesting fructose (fruit sugar) found in fruits, honey, and some sweeteners.
Reaction to foods high in histamine — aged cheeses, fermented foods, alcohol, processed meats.
Reactions to sulfites, MSG, or food colorings that can trigger headaches or asthma symptoms.
If you suspect a food allergy, it's important to see a board-certified allergist for proper diagnosis. Never attempt to diagnose yourself, especially if you've had severe reactions.
A tiny amount of allergen is placed on your skin. Skin is lightly pricked to allow allergen to enter.
Results: 15-30 minutes. A raised bump (wheal) indicates a possible allergy.
Notes: Not painful but may be itchy.
Measures specific antibodies (IgE) in your blood.
Results: 1-2 weeks. Helpful when skin testing isn't possible.
Notes: Less sensitive than skin prick tests.
The most accurate test for food allergy. You eat gradually increasing amounts of the suspected food under strict medical supervision.
Notes: Can confirm if you're truly allergic. Only done by allergists in medical settings.
Your allergist will ask detailed questions about your reactions.
Includes: Information about when, how often, and how severe reactions occur.
Notes: Important part of accurate diagnosis.
Important: Neither skin nor blood tests can predict how severe your reaction might be. Some people test "positive" to foods they can actually eat without problems.
Testing for food intolerances is different from allergy testing and focuses on digestive function.
Most common test for lactose intolerance. You drink a liquid with lactose and breath hydrogen levels are measured over time. High hydrogen levels indicate poor digestion. Also used for fructose intolerance.
Remove suspected foods from your diet for 1-2 weeks. Keep a food diary tracking what you eat and symptoms. Gradually reintroduce foods one at a time and watch for return of symptoms. Should be done under medical supervision.
Measures blood sugar after consuming lactose. If blood sugar doesn't rise, lactose isn't being digested properly.
Record all foods eaten and any symptoms. Look for patterns over several weeks. Simple and non-invasive way to help identify problematic foods.
Many alternative and unproven tests are advertised for food allergies and intolerances. These are NOT supported by scientific evidence and are NOT recommended by medical organizations.
Tests for IgG antibodies (not IgE). IgG indicates food exposure, NOT allergy. A positive result may actually mean you can TOLERATE the food. No scientific evidence for diagnosing food allergies.
Claim to measure changes in white blood cells. No reliable scientific evidence. Not recommended for allergy diagnosis.
Tests muscle strength while holding foods. Claims foods "block energy fields." No scientific basis. Can lead to unnecessary food restrictions.
Uses electrical currents to test for "allergies." No scientific evidence. Results are unreliable.
Examines blood cells under a microscope. Claims cells change shape when exposed to allergens. No scientific evidence.
Injects or places allergen under the tongue to provoke symptoms. Claims larger dose "neutralizes" reaction. Dangerous and unproven. Could cause severe allergic reactions.
Tests hair for mineral content. Not useful for diagnosing food allergies or intolerances.
Claims to measure inflammatory response to foods. Not scientifically validated for allergy diagnosis.
Stick with board-certified allergists who use scientifically proven testing methods.
Completely avoid foods you're allergic to
Always check food ingredient lists carefully
If prescribed, always have your auto-injector with you
Consider a bracelet or necklace identifying your allergy
Tell restaurants, schools, and caregivers about your allergy
Know what to do in an emergency
Regular follow-ups to monitor your condition
Keep a food diary to identify problem foods
You may tolerate small amounts
Lactase pills can help with lactose intolerance
Try lactose-free or reduced-lactose products
Consuming problem foods with meals may reduce symptoms
Ensure you're getting adequate nutrients when avoiding foods
Can help plan balanced meals while managing intolerances
Remember: This information is for educational purposes and should not replace professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment of food allergies or intolerances.
Sources: Mayo Clinic | American College of Allergy, Asthma & Immunology (ACAAI) | Asthma and Allergy Foundation of America (AAFA) | National Institutes of Health (NIH) Guidelines for Food Allergy Diagnosis
Last Updated: January 2025