A food allergy can make you vomit

Food intolerances and food allergies

Food intolerance and Food allergies (Food allergies): Reactions such as itching, rashes, shortness of breath or abdominal pain and diarrhea after consuming certain foods. The causes are either a real allergy, a pseudo-allergic reaction, or digestive disorders such as a lack of certain digestive enzymes.

Food allergies occur in up to 5% of the population, most often in infancy; Women and girls are affected twice as often as men and boys. The allergies trigger complaints in the gastrointestinal tract as well as in the skin, the respiratory tract and the circulatory system. If the allergen can be identified and avoided, the food allergy can completely disappear in children in up to 50% and in adults in up to 30% of the cases.

Food intolerances due to lack of enzymes will also occur Food intolerance called. One example of this is lactose intolerance, where those affected cannot tolerate milk sugar. If the respective foods are avoided, there will be no complaints.

Leading complaints

Allergies and pseudo-allergies:

  • Rash, most common with 50%
  • Itching and furry feeling on the lips and roof of the mouth, less often abdominal pain, vomiting or diarrhea (20%)
  • Allergic runny nose, shortness of breath with swelling of the throat or narrowing of the bronchi (20%)
  • In severe acute reactions: pulse increase and drop in blood pressure with weakness, dizziness, cold sweaty skin up to allergic circulatory shock.

Enzyme deficiency:

  • diarrhea
  • Stomach cramps
  • Flatulence (especially after consuming milk).

When to the doctor

In the next few weeks if

  • you repeatedly react to certain foods with one or more of the symptoms mentioned above, e.g. B. rash, vomiting, or diarrhea.

Call the (emergency) doctor immediately if

  • breathlessness, sweating, weakness, dizziness and / or impaired consciousness occur after eating!

The illness

There are many different reasons why a person may not be able to tolerate a particular food or ingredient. That is why when it comes to food allergies or intolerance, the terms are often misunderstood and mixed up.

Food allergies

At a real food allergy the organism forms antibodies against components of the food (= antigen). If the antigen and antibodies combine to form an immune complex, histamine is released. Histamine in turn causes the typical allergy symptoms such as swelling, redness and itching. The situation becomes dangerous when allergic reactions are so strong that there is difficulty in breathing and allergic circulatory shock.

Trigger. The most common allergens, i.e. foods or ingredients that cause a real food allergy, are milk, eggs, fish and shellfish, but also soy, nuts, various types of fruit and vegetables and flours. Food allergies include B. also the wheat allergy. Often those affected also suffer from pollen allergies, which then trigger food allergies through cross-reactions.

Pseudo allergy

At Pseudo allergies different substances cause a direct release of histamine without the immune system being involved. However, the symptoms are the same.

Trigger. The main triggers of a pseudoallergic reaction are substances contained in food such as

  • Histamine (sauerkraut, cheese, red wine)
  • Serotonin (bananas, walnuts)
  • Tyramine (cheese, fish, tomatoes, avocados, wine, yeast, bananas)
  • Phenylethylamine (chocolate)
  • Food additives tartrazine, benzoic acid and sulfite
  • naturally occurring sulfites (beer, wine)
  • Salycilate (fruit and potatoes)
  • Glutamate (flavor enhancer, especially in Chinese cuisine).

Food intolerance due to lack of enzymes

In addition to allergies and pseudo-allergies, a lack of certain digestive enzymes also leads to food intolerance. The enzyme deficiency is either congenital or arises from damage to the intestinal mucosa.

Milk sugar intolerance (lactose intolerance). Lactose intolerance is a widespread phenomenon that becomes more common with age. Up to 15% of adults in Europe suffer from a congenital deficiency of the enzyme lactase. In the intestine, lactase breaks down milk sugar (lactose) into its two sugar components, glucose and galactose. These are then absorbed by the mucous membrane of the small intestine and transported by the blood to the liver for further processing. If there is a lack of lactase, the lactose that has not been broken down reaches the large intestine undigested. There it is broken down by the intestinal bacteria into lactic acid, carbon dioxide and hydrogen, which causes diarrhea, flatulence and cramp-like pain.

Diseases of the small intestine that damage the mucous membrane (such as in celiac disease) also mean that lactose is not properly digested and absorbed and instead leads to flatulence and diarrhea in the large intestine.

In addition to the frequent lactose intolerance, there are other, rarer enzyme deficiency diseases in which the reduced digestion of galactose, fructose, sorbitol and others. leads to similar complaints.

In the congenital Fructose intolerance (fructose intolerance) If the liver is unable to break down the fructose taken in by fruits and fruit juices due to an enzyme deficiency. Even in infancy, after weaning and the first meals with fruit or fruit juices, severe hypoglycaemia, nausea, vomiting, diarrhea and severe kidney and liver damage occur. Those affected instinctively avoid all foods containing fructose when they are young.

Flatulence, diarrhea and abdominal pain after consuming fruit juices and fruits also occur with the Fructose malabsorption (i.e. the decreased uptake of fructose through the intestinal lining). Here the transport mechanism through the intestinal mucosa is disturbed.

The Galactose intolerance (better Galactosemia) is a congenital metabolic disease in which 3 different enzymes for the breakdown of galactose can be missing. Galactose is split off from lactose in the intestine and is therefore found in both breast milk and cow milk. Affected infants react with diarrhea, vomiting and weight loss from the first feeding. The accumulation of undegraded galactose can cause liver damage and clouding of the lens just a few weeks after birth. That is why newborns are tested for galactosemia immediately after birth (newborn screening). If the test is positive, only an immediate, lifelong galactose-free diet will help, under which the children then develop normally.

In addition to this congenital disorder, galactose intolerance also occurs when the intestinal mucous membrane is damaged by a disease and the absorption of galactose is disturbed as a result. This intolerance only leads to intestinal symptoms such as flatulence and diarrhea.

Wheat Allergy, Celiac Disease, and Wheat Sensitivity

With these three food intolerances, the body reacts to wheat components.

  • In the Wheat allergy The protein components of wheat, such as wheat albumin, wheat globulin and the gluten, are the triggering allergens. In addition to indigestion, symptoms outside the gastrointestinal tract can occur, for example headaches, chronic fatigue, muscle and joint pain. Wheat allergy affects people with chronic inflammatory bowel disease or autoimmune diseases such as multiple sclerosis particularly hard. Studies have shown that wheat proteins make their symptoms worse. The therapy consists of avoiding wheat and related grains such as spelled and green spelled for one to two years. If the allergic reaction occurs again, the patient may have to go without these foods for life. In acute cases, cortisone alleviates the symptoms.
  • The [native] sprue or Celiac disease, also known as gluten-sensitive enteropathy, is based on an autoimmune reaction to the gluten found in many types of grain (adhesive protein). Those affected develop severe intestinal inflammation, so that the intestines can no longer absorb nutrients. The consequences are signs of malabsorption (insufficient supply of nutrients) such as diarrhea and weight loss. Older infants sometimes experience severe failure to thrive shortly after weaning. Skin diseases are also common in celiac disease. In many cases, celiac disease occurs together with lactose intolerance and increases the risk of developing lymph gland cancer. A lifelong gluten-free diet usually makes the symptoms disappear completely; the risk of cancer also decreases.
  • The symptoms of Wheat sensitivity often resemble those of celiac disease. Those affected react to the consumption of wheat products with gas, diarrhea and stomach pain. It is an intolerance reaction, the exact cause of which has not yet been clarified. Diagnosis is made by ruling out wheat allergy, celiac disease, and other food intolerances. As with celiac disease, the therapy consists of avoiding gluten. After 2 years of a gluten-free diet, those affected can test again whether they can tolerate foods containing wheat.

Diagnostic assurance

To find out which foods are causing the symptoms, a food diary is kept for about 3 weeks. If this is not enough to identify the suspicious food, one tries to detect it with a Elimination diet to find. The person affected eats a low-allergen diet based on rice and potatoes for 7 days. If the symptoms subside, a food allergy or intolerance is likely. Then more foods are gradually added to the menu (Search diet)until complaints reappear. If these decrease after omitting the suspect food and occur again after consuming it again, the trigger has been identified.

Skin tests for various allergens and blood tests complete the diagnosis; however, they are often wrong. Therefore, the triggering of the symptoms by the identified food is the most important diagnostic method.

Diagnosis of lactose intolerance

Lactose tolerance test. The diagnosis is obvious if flatulence, abdominal pain and diarrhea occur again and again after consuming milk and dairy products, and these symptoms disappear as soon as the person concerned abstains from these foods. With the lactose tolerance test (milk sugar tolerance test), the doctor proves the deficiency of the enzyme lactase (milk sugar intolerance), which is necessary for milk digestion. The test is cheap and easy to carry out: for the examination, the patient drinks 50 g of lactose dissolved in water in the morning. After 30, 60, 90 and 120 minutes, blood is drawn and the blood sugar level is determined. If there is a sufficient amount of lactase in the mucous membrane of the small intestine, the body absorbs the glucose split from the milk sugar into the blood and the doctor can determine an increase in the blood sugar level. Today, however, the direct enzyme detection in the context of fine tissue examinations of small intestine tissue samples that are obtained by a colonoscopy is increasingly preferred.

Hydrogen breath test. The hydrogen breath test (H2 breath test) also shows how well lactose is broken down in the small intestine by the enzyme lactase. The doctor usually combines this test with the lactose tolerance test. After the patient has drunk a lactose solution, he blows into a device. If there is a lack of lactase, the milk sugar absorbed in the intestine is not sufficiently broken down into glucose and galactose, but reaches the large intestine. There the lactose is broken down, producing hydrogen (H2), which can then be detected in the breath when you exhale.

Diagnosis of fructose intolerance

If a congenital fructose intolerance is suspected, the diagnosis is made through a liver biopsy. The disease cannot be cured; If the person concerned avoids large amounts of fructose, they have a normal life expectancy. Fructose malabsorption (i.e. the disturbance in the uptake of fructose by the intestinal mucous membrane) can be demonstrated, like lactose intolerance, by a hydrogen breath test.

Differential diagnoses: In the case of gas, diarrhea and abdominal cramps in connection with food intake, the doctor must rule out other diseases of the digestive tract, such as: B. Celiac disease, chronic pancreatitis, and Crohn's disease.


Treatment is to avoid the triggering food (s). In many cases, those affected also have to protect themselves against various pollen, to which there is often a cross-allergy. Birch pollen allergy sufferers are often allergic to apples, stone fruits and hazelnuts; while latex allergy sufferers are also allergic to avocados, bananas, figs and peaches.

In the case of lactose intolerance, it is also important to avoid milk and dairy products or - in lighter cases - to consume only a reduced amount. In addition, the person concerned can fall back on lactose-free milk and dairy products.

In everyday life, however, it is not always possible to completely avoid foods in which z. B. milk and eggs are processed. Then drugs that protect the mast cells from histamine release (e.g. Colimune®) or antihistamines can be used. If there are no more than three allergies at the same time, a desensitization helps.

Emergency therapy

Allergy sufferers who have already suffered an allergic shock or suffer from severe asthma should always have an emergency kit with them. With the medication it contains, the patient can deal with a severe allergic reaction until a doctor is on site. Usually are in such an emergency kit

  • Adrenaline in an auto-injector, with which the active ingredient is injected directly into the thigh muscles by the patient or a helper. Adrenaline works within 5–10 minutes, relieves dyspnoea and stabilizes the circulation.
  • Antihistamine, preferably as drops. It relieves itching and has an antispasmodic effect.
  • Cortisone as a spray or tablets. The effect only occurs after about 1 hour, but lasts longer than with adrenaline or an antihistamine.


If the triggering substance is avoided for years, a real food allergy sometimes disappears on its own. Affected children often develop a tolerance to the original allergen with increasing age. Therefore, experts recommend that children be checked annually to see whether the diet is still necessary.

If there is a congenital enzyme deficiency (fructose intolerance, galactosemia, lactose intelorence), a lifelong diet is necessary. Especially with galactosemia - if the diet is not followed, there is a risk of severe damage such as cirrhosis of the liver, motor and mental disorders and blindness.

Your pharmacy recommends

What you can do yourself

Food intolerances have many faces: their severity ranges from negligible in everyday life to the most severe impairments. Accordingly, the following tips can only describe some general measures:

  • Avoid finished products whose tolerability you do not know or whose ingredients you cannot clearly determine.
  • Familiarize yourself with the various names with which the allergy-causing or incompatible substance is identified on the food, e.g. B. the E number for incompatible preservatives.
  • Apps for mobile phones that provide information about food additives are helpful. An example of this is the "E Numbers Food Additives" app for Android or iOS (for a fee).
  • Some foods only cause an allergic reaction when raw. Therefore, whenever possible, give preference to heated food.
  • Many sufferers benefit from the fact that they generally avoid spice mixtures, foods rich in histamine, alcohol and fruit juices.
  • If you are allergic to staple foods or a variety of foods, nutritional advice is recommended. This is where you can find out what alternative foods you can use to meet your daily nutritional needs.

Discuss with your general practitioner or internist whether he can write you a prescription for cortisone (e.g. two tablets of dexamethasone with 8 mg each) for self-treatment in an emergency. You should always carry this medication with you and take it as a precautionary measure in the event of acute intolerance reactions in order to prevent allergic shock.You may also be one of those patients who should carry an emergency kit with an adrenaline auto-injector as a precaution. Your doctor will also provide you with a prescription for this.

Further information

  • www.DZG-online.de - Website of the German Celiac Society, Stuttgart: With information on diet and gluten-free foods.
  • https://www.mein-allergie-portal.com/allgemein/115-allergie-selbshilfegruppen.html - website for those affected, where you can find self-help groups for a variety of food intolerances.


Dr. med. Arne Schäffler, Dr. Bernadette Andre-Wallis in: Health Today, edited by Dr. med. Arne Schäffler. Trias, Stuttgart, 3rd edition (2014). Revision and update: Dr. med. Sonja Kempinski | last changed on at 11:41

Important note: This article has been written according to scientific standards and has been checked by medical professionals. The information communicated in this article can in no way replace professional advice in your pharmacy. The content cannot and must not be used to make independent diagnoses or to start therapy.