Causes of Food Intolerance & Allergies

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Food Allergy and Intolerance

Causes of Food Intolerance and Allergies

Food intolerance is a condition where some people experience digestive issues. Issues like cramps, bloating or diarrhea, for example. These issues occur when eating certain foods. But, there is no allergic reaction in such cases. Although many people use the terms interchangeably, intolerance and allergy are different. Further, there are different causes of food intolerance.

A food allergy is when the immune system of a person reacts to specific foods. As a result, it triggers a set of responses. Differences between food allergy and food intolerance include, for example:

  • Allergic reactions are quick to present themselves. But, food intolerance may have a delayed onset of symptoms.
  • Consuming small portions of ‘intolerant’ food does not cause major problems. However, small portions of food ‘allergic’ food can cause severe reactions. For example, a person allergic to peanuts will have instant allergic reactions. This when they come in close contact with a person who has consumed peanuts. This is also when one eats food prepared in an area that handles peanuts as an ingredient as well.

What is an allergy?

Allergic reactions are the body’s way of responding to external substances. These substances are allergens. While they may not be harmful by themselves, they may trigger a reaction in some people. Also, they can vary in severity from person to person. People may also show different symptoms as well. Further, the life-threatening reaction is anaphylaxis.

What is a food allergy?

A food allergy is the abnormal reaction of the body’s immune system to a particular food. Generally, it presents a host of side effects. While there is no conclusive data, more people assume they are allergic to a certain food. However, it may not be true upon testing. Children with food allergies usually outgrow the condition. An example includes those allergic to cow’s milk. More people report food allergies every year. But their severity varies.

Depending on which part of the immune system responds to it, food allergies can be of different types. Types such as:

  • Antibodies immunoglobulin E (IgE) causes acute and sudden-onset reactions. Histamines are produced. Antihistamines treat this type of reaction.
  • Non-IgE-mediated reactions usually show a delayed onset of symptoms. These reactions are less severe. The white blood cell- called T cells induce this reaction.
  • Some common reactions are abdominal pain and bowel problems. Rashes or eczema are also common reactions as well. You may even have a combination of them.

Symptoms of food intolerance

Food intolerance is where some people experience digestive issues upon consuming certain foods. Issues such as cramps, bloating or diarrhea for instance. There are different causes of food intolerance. But, there is no allergic reaction in such cases.

Irritable Bowel Syndrome or IBS may also cause similar symptoms as food intolerance. Symptoms such as bloating and diarrhea for instance. Certain food additives like MSG or monosodium glutamate directly affect the body. They may result in headaches, bloating, abdominal pains or flushing. It is sometimes unclear what triggers the symptoms.

Lactose intolerance

One common cause of food intolerance is lactose. Lactose intolerance is a disorder of the digestive system. It is where a person is unable to digest lactose. Lactose is the main carbohydrate in dairy products and milk. People with this condition are unable to secrete the enzyme lactase. This enzyme is necessary to digest lactose. Symptoms of lactose intolerance include bloating and abdominal pain. It also includes diarrhea as well. The trigger is the consumption of milk or dairy products.

Food avoidance as a remedy

Vomiting and diarrhea may happen when people eat food they dislike. While this may not be intolerance to the food per se, it makes it difficult to classify what brings on the symptoms. One may end up excluding foods that are important. Even though they do not trigger any allergic reactions. This happens especially in young children. Such practices may affect their growth, or they may even develop malnutrition.

Mouth and throat (oral) allergy syndrome

Fresh fruit, certain vegetables, and nuts can cause an allergic reaction. It is confined to the mouth and throat area in some people. Common reactions are, for example, swelling of the tongue and lips. In addition, sudden obstruction of the airway is also common. Some people confuse this with anaphylaxis.

Eating certain foods in their raw form may trigger swelling of the tongue and throat. But it is usually safe for the person to consume the same foods after cooking. This is because it destroys the allergy-inducing proteins in the process. The symptoms appear quickly but settle down greatly within an hour. People who get hay fever are likely to suffer from oral allergy syndrome as well. Seek medical help immediately if you feel like you are unable to breathe. Additionally, seek medical help if you feel faint or feel like your throat is constricting.

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Symptoms of food allergy

Some of the symptoms when a food allergy is due to an IgE allergic reaction include:

  • Itchy, watery eyes
  • Nausea or vomiting
  • Feeling out of breath, wheezing
  • Tingling in the mouth
  • Swelling of the lips, tongue or throat
  • Itchy skin or rashes. Also, feeling flushed
  • Abdominal pain
  • Diarrhea
  • Runny nose, Sneezing
  • Feeling dizzy and light-headed
  • Swelling around the eyes

Further, the onset of these symptoms are quick. For instance, they can happen right after eating the trigger food. 

Some of the symptoms when a food allergy is due to non-IgE allergic reaction include:

  • Persons with hay fever/asthma may get atopic eczema
  • Gastroesophageal reflux or effortless vomiting
  • Diarrhea or constipation
  • Mucus or blood-stained stool
  • Redness around the anus
  • Being pale or feeling tired
  • Poor growth (especially in children)

Which foods cause most allergies?

Foods that commonly cause allergies:

  • Milk
  • Nuts (mainly peanuts)
  • Eggs
  • Shellfish
  • Seafood
  • Sesame
  • Citrus fruits
  • Kiwi
  • Soy
  • Wheat


If you suspect you or your child may have a food allergy, bring it up with your doctor. A referral to a specialist or for testing to confirm a diagnosis may be necessary. This is if:

  • A severe allergic reaction occurred
  • If a child is not growing well
  • It there are gastrointestinal symptoms

Also, if you suspect you may have food intolerance, try to find the trigger food on your own. This is based on observance. Do this if the symptoms are mild. In severe cases, seek medical help immediately.

Food diary

Write everything you eat during the day. Note any triggered reactions. This method may not be conclusive. But, it can shed light on problematic foods and how they affect you. It can also shed light on causes of food intolerance.

Specific tests

There are skin prick and blood tests are done. This is if one suspects to have an IgE-mediated allergy.

How skin prick tests work

Specialists perform the skin prick test in a hospital setting. There is access to resuscitation equipment. Also epinephrine injections are readily available.

  1. A solution is prepared by mixing the allergens with a liquid.
  2. One drop of this liquid is placed on the hand of the person. A needle gently pricks under the drop. An insignificant amount of the allergen then enters the bloodstream.
  3. Clinicians check the skin for any allergic reaction.
  4. If the skin becomes red and itchy, the reaction is positive. If the test causes the skin to erupt in wheals then it also means the reaction is positive as well. This should go away in a few hours.

Blood tests

Blood tests can be expensive. And they can also be nonconclusive. The test may detect if specific IgE antibodies are present in your blood. IgE antibodies like those for peanuts as an example.

Blood tests are safe in people who have anaphylaxis. Additionally, they are also recommended for those with severe skin diseases as well. The major drawback of this method is that they work well for testing only a few allergens.

Elimination and challenge

In this method, food that is suspected of triggering the reaction is eliminated from the diet for 2-6 weeks. Check if the symptoms have reduced drastically. Reintroduce the suspected food to the diet. Then check if the symptoms return to determine the cause of food intolerance.

Talk to your physician before attempting the elimination method. Continue eating a balanced diet.

Placebo-controlled food challenge tests are expensive. They are also difficult to execute. Therefore, it is not widely recommended. This requires several days of monitoring. One is also required to drink a solution as well. Every dosage contains more of the allergic food than the previous dose. It is randomly replaced with nonallergic food over the course of a few days. The test must be done in a facility where emergencies can be treated. This is in case the reaction quickly escalates.

Treatment for food allergies

  • Antihistamines are a class of drugs. They suppress any untoward allergic reaction.
  • Avoid allergy-inducing foods.
  • If you have a severe allergy, always carry an epinephrine injection with you.
  • A medical bracelet citing all the allergies can be worn on the wrist for emergency situations.

Referral to a dietician

Dieticians can diagnose and treat dietary problems. They are qualified health professionals. Nutritionists and therapists, however, register voluntarily. They also largely base their treatments on personal beliefs and opinions.

Once the specialist provides a recommendation to avoid a particular food due to an allergy, a dietician helps you in continuing to eat a balanced diet. This is especially true for children. As it can seriously affect their growth and development.


Most allergies become more manageable after a few years. This is based on avoidance. It is also based on the immunity system getting more mature as well. Young people with an allergy to milk, eggs, soy, wheat, etc typically outgrow the condition as they get older. Only people with allergic reactions to certain foods rarely see improvement in their condition. Foods like fish, seafood, and peanuts for instance.

Celiac disease

Autoimmune diseases are not outcomes of a food allergy or intolerance. They are conditions where the immune system attacks itself. It mistakenly does this rather than foreign substances. For instance, one commonly occurring disease in the US is Celiac disease. It is often caused by a sensitivity to gluten in products. Products such as pasta and bread can cause bloating or cramps. This is until the food particle is removed from the body.

Peanut allergy, pregnancy, breastfeeding and weaning

Due to the lack of conclusive research findings, pregnant women do not need to avoid eating peanuts. This applies to breastfeeding women as well. This is as long as they are not allergic to the peanuts themselves.

The World Health Organization (WHO) advises that:

  • Mothers only breastfed their babies for the first six months of life.
  • If weaning on to solid food happens before six months of age, avoid peanuts and nut-containing foods.
  • Also avoid foods with seeds, cow’s milk, eggs, wheat, fish and shellfish as well.
  • When a child is no longer breastfeeding, it is best to introduce one new food at a time. This helps in zeroing in on an allergy-inducing food easily.

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