Understanding Food Allergies and Intolerances: Symptoms, Diagnosis, and Treatment

Alan Lucks | MD

Medically reviewed by Alan Lucks | MD, Alan Lucks MDPC Private Practice - New York on August 28th, 2023.

Key Takeaways

  • True allergies involve IgE antibody responses that can trigger anaphylaxis within minutes, while intolerances stem from enzyme deficiencies (like lactase deficiency affecting 65% of adults) causing digestive symptoms hours later.
  • The "Big 8" allergens—milk, eggs, peanuts, tree nuts, wheat, soy, fish, and shellfish—account for 90% of serious allergic reactions, with peanuts and shellfish being the most likely to cause fatal anaphylaxis.
  • Oral food challenges conducted in medical settings remain the gold standard for diagnosis, as skin prick tests can show false positives in up to 50-60% of cases.
  • Epinephrine auto-injectors must be administered within 3-5 minutes of anaphylaxis onset and injected into the outer thigh muscle—antihistamines like Benadryl cannot stop severe allergic reactions.
  • Cross-contamination occurs in as little as 1/1000th of a peanut for highly sensitive individuals, making "may contain" labels and dedicated manufacturing facilities critical safety considerations.

Many people experience unpleasant reactions after eating certain foods and may think they have a food allergy. However, they may actually have a food intolerance. It's important to understand the difference between food allergies and intolerances to properly manage your condition.

What Is a Food Allergy?

A food allergy is caused by your immune system reacting to a specific food protein. When you eat the food, your body produces antibodies called immunoglobulin E (IgE), which trigger the release of chemicals like histamine. This can cause various symptoms throughout your body.

Common Food Allergies

The most common food allergies in adults include:

  • Peanuts

  • Tree nuts (e.g., walnuts)

  • Shellfish (e.g., shrimp, crayfish, lobster, crab)

In children, the most common food allergies are:

  • Eggs

  • Milk

  • Peanuts

Symptoms of Food Allergies

Symptoms of food allergies can range from mild to severe and may include:

  • Itching in the mouth

  • Vomiting, diarrhea, or abdominal pain

  • Drop in blood pressure

  • Hives or eczema

  • Wheezing or difficulty breathing

Severe allergic reactions (anaphylaxis) can be life-threatening and require immediate medical attention.

Understanding Food Allergies and Intolerances: Symptoms, Diagnosis, and Treatment

What Is a Food Intolerance?

A food intolerance is not caused by the immune system but is usually a problem with digesting the food. For example, lactose intolerance is caused by a lack of the enzyme lactase, which is needed to digest the sugar in milk and dairy products.

Diagnosing Food Allergies and Intolerances

To diagnose a food allergy or intolerance, your doctor may:

  • Ask detailed questions about your reactions and eating habits

  • Recommend keeping a food diary to identify patterns

  • Suggest an elimination diet to pinpoint the problematic food

  • Perform skin prick tests or blood tests to measure your allergic response

  • Conduct a food challenge under medical supervision

Treating Food Allergies and Intolerances

The main treatment for food allergies and intolerances is to avoid the offending food. This requires careful reading of ingredient labels and communication with restaurant staff about food preparation.

For severe allergies, you should carry an epinephrine auto-injector (e.g., EpiPen) and wear a medical alert bracelet. Mild symptoms can be treated with antihistamines or bronchodilators.

Researchers are studying allergy pills and shots as a way to desensitize people to food allergens, but these treatments are not yet proven effective.

Managing Food Allergies in Children

Milk and soy allergies are common in infants and young children. These allergies may cause colic, blood in stool, or poor growth. Breastfeeding for the first 4-6 months may help prevent allergies, but there is no conclusive evidence.

Parents and caregivers should protect children from trigger foods and have emergency plans in place. Schools should also have protocols for managing food allergies.

For more information on food allergies and intolerances, visit:

The Bottom Line

Accurate diagnosis through proper medical testing is essential since the management strategies for allergies versus intolerances differ significantly—one requires emergency medications while the other may only need enzyme supplements. Reading ingredient labels meticulously and understanding your specific triggers can prevent both uncomfortable symptoms and life-threatening reactions. If you're experiencing unexplained symptoms after eating, Doctronic can help you determine whether you need allergy testing or other evaluations.

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