Features of allergy and intolerance

The table below shows features associated with either a food allergy or an intolerance.

Intolerance Allergy
Onset Symptoms appear later. Symptoms appear soon after eating the food, usually within 2hours, but sometimes after 4–6 hours.
Amount The person can eat a very small quantity of the food with no adverse reaction. The person cannot tolerate even small amounts of the allergen or food they are allergic to. Exposure to even a tiny amount of the food will produce a severe reaction.
Exposure A reaction will occur only if the person eats the specific food. A reaction may occur if the person eats a food that someone prepares for them in an environment that contains the allergen.
Effect Reactions can be severe and extremely unpleasant but are rarely life-threatening. Severe and potentially life-threatening reactions that may include anaphylaxis (anaphylactic shock).
Common trigger foods
  • Beans
  • Cabbage
  • Citrus fruit
  • Grains that contain gluten
  • Milk, or lactose
  • Processed meats
  • Eggs
  • Fish
  • Groundnuts, or peanuts
  • Milk
  • Tree nuts (Brazil nuts, walnuts, almonds, and hazelnuts)
  • Soybeans
  • Shellfish
  • Wheat

An immune response or an enzyme deficiency?

Food allergies and intolerances are unwanted reactions to food that some people experience, but they are not the same and happen for different reasons.

Nuts are a common trigger food for people with allergies.

Immune response: When a person has a food allergy, their body’s immune system responds incorrectly to a substance known as an allergen.

An allergen is not necessarily a harmful substance. Doctors call them allergens because they trigger an immune system response in certain people. However, allergens do not cause an adverse effect in most people.

According to the United States ;FDA the following foods are most likely to cause a reaction:

  • milk
  • eggs
  • peanuts (groundnuts)
  • Brazil nuts, walnuts, and hazelnuts (tree nuts)
  • fish
  • shellfish
  • wheat
  • soybeans

Enzyme deficiency: A food intolerance usually means that a person has an enzyme deficiency.

Enzymes are substances in the body that enable people to digest food. If a person has an enzyme deficiency, their body cannot digest certain foods properly. The problematic food depends on the enzyme that is lacking.

Food intolerance may also result from:

  • certain chemicals in foods
  • food poisoning  due to the presence of toxins
  • the natural occurrence of histamine  in some foods
  • the presence of salicylates that occurs in many foods
  • specific food additives

In summary, prevention means:

  • A person with a known allergy must avoid the trigger food. Not doing so could be dangerous. The person also should carry an epinephrine autoinjector for use in case of an emergency.
  • A person with an intolerance can avoid discomfort by avoiding the trigger food, but they will not face a life-threatening situation.

Since 2004, the Food Allergy Labeling and Consumer Protection Act (FALCPA) states that all packaged foods that manufacturers produce in the U.S. must carry information in simple, clear language about the eight most common allergens.

These widespread allergens are milk, eggs, wheat, soy, peanuts, tree nuts, fish, and crustacean shellfish.


Celiac disease

Celiac disease affects about 1% of the Western population. In this autoimmune condition, the ingestion of gluten initiates a complex inflammatory reaction that can make people with celiac disease very sick. Celiac disease is not a true allergy; eating gluten once does not cause an immediate life-threatening problem. However, prolonged and continuous ingestion can cause diarrhea, weight loss, and malnutrition.

Avoiding gluten is the only solution to this problem. Gluten is found in a variety of grains, including wheat, rye, barley, semolina, bulgur, and farina. Many processed foods also contain gluten. People with celiac disease must also be careful about cross-contamination, when a gluten-free food comes into contact with a gluten-containing food.

Food sensitivities

After eating certain foods, a large part of the population experiences symptoms that are not related to food intolerances, food allergies, or celiac disease. These are referred to as food sensitivities. Though there is controversy around what exactly happens in the body of someone with a food sensitivity, it appears that exposure to specific foods may create an immune reaction that generates a multitude of symptoms. The symptoms are not life-threatening, but they can be quite disruptive and include joint pain, stomach pain, fatigue, rashes, and brain fog. Gluten is probably the best-known trigger of food sensitivities.

The best tool we have to identify food sensitivities is a process of careful observation and experimentation. Removing certain foods believed to cause reactions from the diet for two to four weeks, reintroducing them one by one, and watching for symptoms is the current gold standard to pin down what may be causing symptoms. This so-called “elimination diet” is not high-tech, and it is far from perfect. A physician or nutritionist can provide guidance for undertaking an elimination diet, and can help you understand limitations and avoid possible pitfalls. Removing certain foods can help stave off undesirable symptoms and improve your quality of life.

Food reactions, especially sensitivities, can also fade away with time. Our bodies, immune systems, and the gut microbiome are continually changing, and what may not sit well today may be fine to have later on in life. At some point, you may consider reintroducing small amounts of a food that you have been sensitive to, to see what you may be able to tolerate.

For Appointment with

Dr. Hesham Farouk

Call 044400500