Is it a food allergy or an intolerance?

A food allergy is different from food intolerance, although some people may not always know how these vary. A food allergy involves an immune system response by the body, while a food intolerance does not.
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A person with a food intolerance cannot digest a substance in certain foods properly, often because they have an enzyme deficiency. A food allergy does not relate to an enzyme deficiency.
food allergy
Features of allergy and intolerance
The table below shows features associated with either a food allergy or an intolerance.
within 2 hours
anaphylaxis
Beans
Cabbage
Citrus fruit
Grains that contain gluten
Milk, or lactose
Processed meats
Eggs
Eggs
Fish
Groundnuts, or peanuts
Milk
Tree nuts (Brazil nuts, walnuts, almonds, and hazelnuts)
Soybeans
Shellfish
Wheat
Food allergies and intolerances are unwanted reactions to food that some people experience, but they are not the same and happen for different reasons.
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 Food and Drug Administration (FDA), the following foods are most likely to cause a reaction:
Food and Drug Administration (FDA)
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
food poisoning
the natural occurrence of histamine in some foods
histamine
the presence of salicylates that occurs in many foods
specific food additives
Symptoms
Food allergies and food intolerance have different symptoms.
According to the FDA, an allergic reaction to food can cause:
the FDA
hives
hives
itchiness
swelling of the face, lips, and tongue
swelling of the throat and airways, leading to breathing difficulties
dizziness, lightheadedness, and fainting
gastrointestinal symptoms, including vomiting and diarrhea
diarrhea
a sudden drop in blood pressure
blood pressure
a fast, irregular pulse
pulse
a loss of consciousness
If swelling occurs in the airways, this can make it difficult for a person to breathe. If the airway closes, this can become fatal.
An allergic reaction can happen suddenly. If a person shows symptoms of an allergic reaction, they need medical help immediately.
allergic reaction
The main symptoms of a food intolerance are:
main symptoms
intestinal gas
abdominal pain
diarrhea
Other symptoms may occur, but the core symptoms relate to a person’s gut.
Some symptoms of food allergy and food intolerance can be similar. This makes an accurate diagnosis more difficult.
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dedicated hub
Treatment
If a person reacts to a food, the treatment will depend on whether they have an allergy or an intolerance.
A person with an allergy may have a mild reaction on one occasion and a severe reaction on another occasion. About 20 percent of people with an allergy have a severe reaction.
20 percent
Anaphylaxis can range in severity from mild to life-threatening. It can happen quickly and is a medical emergency.
The symptoms of anaphylaxis include:
skin reactions
swelling
difficulty breathing
a sudden drop in blood pressure
Anyone who knows they have an allergy and may have a severe reaction should carry an injector, such as an EpiPen, that delivers epinephrine, or adrenaline. The should carry two doses in case one is not sufficient.

A food intolerance will not usually need urgent treatment. The best treatment is a long-term plan to manage the problem.
Managing an intolerance usually starts with an exclusion diet. This is when a person avoids a food that may be causing the problem for some time, usually 2 to 6 weeks.
The individual may benefit from keeping a food diary to record whether their symptoms improve. After this, they reintroduce the food and note any new reactions.
People may need to repeat this monitoring with different food items to pinpoint which food is causing the problem.
Sometimes, people can reintroduce a food without any reaction occurring. It may be that they develop a tolerance, or that a small amount of the food does not cause a problem any longer.
Food intolerance varies widely between individuals, and so each case is likely to have its own characteristics. Sometimes, an underlying problem makes the intolerance worse and needs appropriate treatment.
Prevention
If a person has a food allergy or an intolerance, they may have to avoid the food that appears to cause it. They may also have to check the ingredients of food products carefully, whether buying for home consumption or eating out.
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.
How common are the conditions?
There has been concern recently that the cases of allergy and intolerance are rising.
The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH) report that around 5 percent of children and 4 percent of adults have a food allergy.
5 percent
In 2016, the Centers for Disease Control and Prevention (CDC) estimated that 6.2 percent of the population had experienced a food allergy in the previous 12 months.
6.2 percent
However, in 2017, a study of electronic health records of more than 2.7 million people in the U.S. suggests that the percentage of the population with either an allergy or intolerance is lower than this, at 3.6 percent overall.
2.7 million
People may not always be aware of the difference between an allergy and an intolerance, and they may not always report an allergy or intolerance to their doctor. For these reasons, it can be difficult to establish exact figures.