Skip to content

What’s the difference between food allergy and food intolerance?

whats the difference between food allergy and intolerance

Food Allergy

Food allergy is caused by the body’s immune system reacting adversely to the consumption of a specific food. Symptoms occur shortly after a food is placed in a person’s mouth. Initial symptoms include oral itching, tingling, and swelling. Symptoms typically occur within seconds to minutes after the food is placed in the mouth. Symptoms may progress into facial swelling and hives. If the food is swallowed, nausea and vomiting may occur. Symptoms may worsen, resulting in faintness and a drop in blood pressure.

Food Intolerance

Food intolerance encompasses a wide variety of adverse reactions following food consumption. These reactions are often not caused by the body’s immune system. Intolerances may be classified as gastrointestinal, metabolic, chemical, or toxic. Gastrointestinal disorders include gluten intolerance (celiac disease) and colitis. Metabolic disorders include lactose intolerance and carbohydrate malabsorption. Chemical disorders include reactions from MSG and food dyes. Toxic reactions occur from eating spoiled foods.

Identifying Food Allergens

People often have a strong suspicion of their specific food allergy. Patients explain that every time they consume a certain food, the same symptoms occur. Symptoms occur quickly after exposure, and they resolve by the next day. Common food allergens in adults include:

  • peanuts
  • tree nuts
  • shellfish
  • finned fish
  • raw fruits

Children may additionally be allergic to:

  • cow’s milk
  • hen’s eggs

These allergies can be quickly identified by allergy testing.

Diagnosing Food Intolerance

Food intolerance can be difficult to diagnose. Allergy testing does not identify food intolerance. Because of the wide spectrum of food intolerances, a careful history must be taken in order to identify a specific diagnosis. Elimination diets are sometimes needed to identify the specific food trigger. Consultation with a gastrointestinal specialist can help aid in the diagnosis of gluten intolerance and colitis. The patient’s story often guides the clinician’s path in establishing the diagnosis.

Allergies & Eczema

what is eczema

What is eczema?

Eczema is a complex disorder of the skin that causes inflammation and itchy rashes. Eczema symptoms include a dry, itchy, red rash on the face, arms, or legs, especially in the folds of the knees and elbows. Patients with eczema exacerbate the disorder by itching and scratching at their skin. Eczema triggers include food, airborne pathogens and bacterial products.

Food allergy and eczema

Incidence of eczema have increased significantly in the past thirty years. In the U.S. today, about 1 in every 10 infants has eczema. Studies of eczema in infants are varied, but suggest that in approximately 40% of infants with eczema, food allergies are also prevalent. In children with severe eczema, food allergy is even more prevalent. Therefore, all infants with persistent eczema should be seen by an allergist and evaluated for food allergies.

Most common food allergies in people with eczema

Of young children with food allergies and eczema, 90% have an allergy to one of the following foods:

  • cow’s milk
  • hen’s eggs
  • soy
  • wheat

For adults and older children, allergy-related eczema flares are more often caused by inhaled allergens like pollen and dust mites. (NOTE: Air purifiers don’t work as well to eliminate dust mite allergens because the particles are so large.)

Eczema treatment plan

  1. Make an appointment with an allergist for yourself or your child with eczema.
  2. Antihistamines may provide some itch relief.
  3. Topical cortisone creams help to control skin inflammation.
  4. Antibiotics may be prescribed if there is a secondary infection.
  5. Avoid proven food allergens in your diet.
  6. Hydrate skin with moisturizer.

Call 888-227-3762 to make an appointment with a Pentucket Medical Allergist today!

Is there a cure for food allergy?

Well, it depends on the type of food someone is allergic to.

Recently there has been information in the press about advances in peanut allergy treatment. Researchers are currently studying the effects of giving multiple small doses of peanut in attempt to cure the allergy. Although this therapy may work in some patients, the rate of treatment-related side effects is quite high. Even in patients who respond positively to this treatment, it is unclear if their desensitized state will be maintained for long periods of time. Due to the high rate of side effects and unclear duration of improvement, desensitization therapy for peanut allergy is not currently standard of care. Allergists continue to recommend avoidance of peanut consumption if a patient has peanut allergy.

On the other hand, allergies to fruits and vegetables have a more promising prognosis. Oral itching after eating foods such as raw apples, cherries, and carrots is a common complaint in New England. Cooked forms of these foods are often tolerated. These symptoms are termed the “Oral Allergy Syndrome”. Patients who have a severe allergy to pollen often complain of itching or swelling of the mouth after eating raw fruits and vegetables. This is caused by structural similarities between pollen and raw fruits and vegetables. Cooking these foods changes their structure, making them less allergic. Because pollen allergy is the cause of this syndrome, reducing pollen sensitivity often improves food-related symptoms. Many patients who undergo 2 or more years of pollen desensitization, or “allergy shots,” report an improvement in their fruit and vegetable allergy.

Although a definitive cure for all food allergies is not yet available, there is hope for people who suffer from raw fruit and vegetable allergy. Please contact your local allergist for more information.

The Real Deal on Food Allergy Testing

food allergy testing information

The proof is in the eating!

Food allergy is a clinical diagnosis. It is not a laboratory or skin testing diagnosis. The proof is in the eating, not the testing. Skin tests and lab tests are based on probabilities, not absolute certainties.

Lab Tests

IgE (the allergic antibody) grades and classes (Class 1, Class 2, Class 3, etc.) and terms like low, mild, moderate and severe are arbitrary and may vary from one laboratory to another. Pentucket Medical Allergy does not use such subjective grades or classes.

IgE is measured in Ku/Liter, or “units”.

IgE levels that indicate a 95% chance of an allergic reaction are:

  • Egg White 7 units 2 units if under two years old
  • Peanut 14 units
  • Milk 15 units 5 units if under two years old
  • Soy 30 units
  • Tree Nuts 15 units
  • Fish 20 units
  • Wheat 26 units

IgG is not an allergic antibody. Therefore, allergy testing with IgG is meaningless.

Skin Tests

95% chance of allergic reactions:

  • Egg 7mm or larger
  • Peanut 8mm or larger
  • Milk 8mm or larger

BE AWARE of Unacceptable Food Allergy Tests!

Testing predicts the likelihood of a reaction, not the severity. Testing can and often is falsely positive. For this reason, patients should not generally be tested for foods that they tolerate or that they have never previously eaten.

One form of food allergy skin testing, called the intradermal test, is not recommended by the American Academy of Allergy because of extremely high false positive rates and risk of reactions to the testing itself. If your allergist suggests intradermal testing for food allergies, you should seek a second opinion.

Food allergy testing cannot help with food intolerances, such as lactose intolerance. Intolerance is an unpleasant reaction to food that is NOT caused by an allergic reaction.

Remember, a patient isn’t diagnosed with a food allergy just because of a positive skin or laboratory test. If a patient is able to eat a food with no symptoms or reactions before testing, they can eat the food after testing.


Get more information, office hours and locations, and meet the Pentucket Medical Allergy team on our website!