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by immune mechanisms caused 

hypersensitivity reaction


Allergyis an immediate or delayed reaction, causing tissue irritation or inflammation, due to the body's counter-reaction to a foreign substance (antigen)   that has entered the body.



Ronald Hoffman MD

Prepared by Sandra Tamm




The food we eat is vital to us because it supplies us with the nutrients we need and gives us energy. Sometimes, however, certain foods can cause us various health problems, so very often, when it comes to a delayed hypersensitivity reaction, for example, the symptoms (for example, headache) are not associated with the food.


Keywords (2,9,11,13,14) :


Hypersensitivity to food- any adverse reaction to food.


Allergy- is a hypersensitivity reaction triggered by immune mechanisms. Allergy can be antibody or cell mediated. IgE antibodies are mostly responsible for allergic reactions and these individuals suffer from IgE-mediated allergy. In non-IgE-mediated allergy, the antibodies may be of the IgG class. Allergic contact dermatitis is a representative of lymphocyte-mediated allergic diseases.


Allergology- is a science that studies the causes, mechanisms of development, manifestation, treatment problems of allergic diseases. The first descriptions of allergic diseases come from Egypt 3600-3300 BC, but allergology itself is a young science and the concept of allergy was introduced only at the beginning of the 20th century.


Antibodies (different types)


IgA- prevent the invasion of viruses and bacteria into the body, they also help prevent the development of food allergies.

IgM- come to the aid of the body at the beginning of the infection and then disappear

IgG- are found in the body for a long time after suffering from infections. A high level of IgG against specific foods can, among other things, confirm the increased use of this food, as well as the fact that a person rather tolerates a specific food. This antibody enters the bloodstream after a meal, and they also enter the blood in healthy people. 

IgE is produced by the allergic organism against allergens, and IgE-type antibodies provide protection against parasites.


Irritation or simple contact dermatitis- is a non-immunological inflammatory reaction of the skin that occurs due to the direct cytotoxic effect of irritating chemicals and physical factors.


Allergic contact dermatitis- is a T-cell-mediated disease and a prototype of a late-type immunological response. Epicutaneous tests are used to distinguish between diseases.


Non-allergic hypersensitivity to food- reactions to food that are not related to the immune system. Food intolerance.


Allergens- are antigens that cause allergies. Most allergens that react with IgE or IgG class antibodies are proteins, but in some cases pure carbohydrates are said to be allergens as well. In allergic contact dermatitis, the classic allergens are low molecular weight chemicals, e.g. chromium, nickel, formaldehyde, which induce T-cell reactions.


Atopy- have a personal or family tendency to produce IgE antibodies in response to low doses of allergens (mostly proteins). The result is typical symptoms such as asthma or allergic eczema/dermatitis syndrome. The terms atopy and atopic are used to describe this clinical feature and predisposition. The term atopy should be used with caution until IgE-type sensitization is confirmed. Allergic symptoms in a typical atopic person can be called atopic, e.g. atopic asthma. IgE-mediated asthma should generally be called atopic asthma. 


Asthma- is a chronic inflammatory disease of the respiratory tract in which many cells, especially mast cells, eosinophils and T cells, are involved. In susceptible individuals, this inflammation causes repeated episodes of wheezing, shortness of breath, chest tightness, and coughing, especially at night or early in the morning. These symptoms are usually accompanied by widespread but intermittent airflow obstruction that is at least partially reversible either spontaneously or with treatment. This inflammation is also accompanied by an increase in airway sensitivity to various stimuli. Allergic asthma is the basic term for asthma caused by immune mechanisms. If IgE-mediated mechanisms are proven, the term IgE-mediated asthma is recommended. IgE antibodies can induce both immediate and delayed asthmatic reactions. However, T-cell responses appear to be important in late and delayed responses. Based on the duration of the symptoms, asthma can be either intermittent or permanent. 


Eczema- the commonly known "atopic eczema/dermatitis" is not a single disease, but a set of different diseases with characteristic common features. A more accurate term is atopic eczema/dermatitis syndrome.



A very common belief is that food allergies only affect those people who immediately experience visible/perceptible ailments when consuming certain foods. Theron Randolph, MD, who is dedicated to allergy research, has pointed out that food allergy is one of the most underdiagnosed diseases today. Why is it like that? In some cases, the symptoms may appear several days later from the moment you have consumed the allergen - this is a delayed hypersensitivity reaction. Therefore, if it is not an immediate reaction, it is very difficult to track down the cause of the problem (3).

For example, if you eat something that you are allergic to and your body reacts to it within a few minutes, you can easily reach a "sickness".  However, since allergy tests only look for IgE antibodies in the blood, many people have a delayed allergic reaction, which is mediated by other antibodies, undiagnosed. In addition, since the symptoms are sometimes very similar both in the case of an allergic reaction and a food intolerance, it is often very difficult to reach the causes.



An allergy is a reaction to a foreign substance or antigen that has entered the body (1).  The main cause of classical allergy is an immune reaction, in which the body is mostly active with IgE antibodies - in this case it is called IgE-mediated food allergy (1,4). Not only IgE antibodies may be involved in the development of food allergy, but also other antibodies, these reactions are called non-IgE-mediated food allergy (1). Allergy can manifest itself a few minutes or hours after eating food, but also only after the end of the day. According to this, fast and slow types of allergic reactions are distinguished (7). 


Food allergy that is not IgE mediated (slow-type allergic reaction) is much less talked about. IgE-mediated food allergy is mostly focused on, while other antibodies (IgM, IgG, IgA, IgD), immune complexes or immune cells are involved in the delayed reaction

(T cells) (3). For example, IgG antibodies are active in celiac disease and IgA in dermatitis herpetiformis (1).


An immediate reaction to food can cause or aggravate allergic diseases such as atopic eczema (atopic dermatitis), asthma, year-round allergic rhinitis, chronic sinusitis. 


Delayed reactions are often called food intolerance, as the word "allergy" causes confusion. True food allergy is different from delayed allergy or latent food allergy, and since the use of the word "allergy" in this context causes problems and confusion, the term "food intolerance" has been accepted(1). On the other hand, however, this is again misleading, since food intolerance is not an immunological reaction (7).


Dr. Kaja Julge also notes in her article that it is somewhat misleading that the word "allergy" has lost its original biological meaning in everyday speech and has acquired more the meaning of intolerance and even intolerance (11).



Hypersensitivity reactions are divided into four types depending on immune mechanisms (1, 3, 4, 8, 11) and are also associated with autoimmune diseases (8):



  • Type I - IgE mediated, symptoms occur within a few hours.  Examples of related diseases: atopic eczema, allergic urticaria, allergic rhinitis (or allergic rhinitis), allergic asthma, anaphylaxis, food allergy, eosinophilic esophagitis 

  • Type II-  cytotoxic, i.e. damaging cells, it is not an allergy. IgM and IgG involved in reactions; Example of associated disease: autoimmune hemolytic anemia, Graves' disease, myasthenia gravis, etc.

  • Type III- Mediated by antigen-antibody complexes - such reactions can damage various tissues. N: Immune complexes deposit on blood vessel walls and damage them. May also be IgG mediated;

  • Examples of related diseases: reactive arthritis, serum sickness, systemic lupus, rheumatoid arthritis, etc.

  • Type IV - cell-mediated slow-type response, mainly involving T cells. Symptoms may appear within 48 - 72 hours.

  • Examples of related diseases: allergic contact dermatitis, Hashimoto's thyroiditis, Crohn's disease, Guillain-Barré syndrome, multiple sclerosis, type I diabetes, etc.



A word"allergy"has lost its original biological meaning in everyday speech and has acquired more of a sense of intolerance and even intolerance.




dr. Echo Courageous



In addition to food, a person can be allergic to pollen, pet dander, house dust mites, household chemicals, solar radiation, that is, as stated above, an allergy is a hypersensitivity reaction to an agent. Allergy manifests itself as many different symptoms, but it can also manifest itself as different diseases. It is also important to note the presence of cross-reactions in the case of allergies, which is the most common flower pollen allergy_cc781905-5cbb-3b-3194 -136bad5cf58d_when, in addition to pollinosis, symptoms of the disease may also appear when eating some food. The key role here is played by IgE antibodies, i.e. protective bodies that recognize the allergen that has entered the body. In the case of cross-allergy, the antibodies also recognize proteins similar to the allergen that entered the body.  The stronger the signs of respiratory allergy disease, the more likely the development of cross-allergy symptoms is (6). In the case of pollen allergy, one of the symptoms of cross-reaction is a tingling and itching sensation in the mouth when eating certain fruits and vegetables, or oral allergy syndrome (1).

































Examples of different diseases in case of allergy (1,7):


  • asthma

  • oral allergic syndrome

  • allergic rhinitis

  • allergic conjunctivitis

  • atopic dermatitis

  • urticaria or urticaria

  • anaphylaxis


Immediate immune reaction   (IgE mediated), can be potentially life-threatening! Some examples of symptoms (10):


  • Redness

  • Itching

  • Laryngeal swelling

  • Eczema

  • Chest pains

  • Nausea

  • Abdominal pain

  • Vomiting

  • Diarrhea


Symptoms caused by a delayed immune reaction   (non-IgE mediated) may include (including autoimmune diseaseceliac disease)(10):


  • Stomach gas

  • Flatulence

  • Chronic diarrhea

  • Acne

  • Dry skin

  • Heartburn

  • Mood changes (irritation, etc.)

  • Headache (including migraines)

  • Anemia

  • Nutrient deficiency

  • Weight loss, etc.






































Diagnosis (2, 7, 12, 13)




Food allergy research begins with an inquiry into which food may have caused the allergic reaction. Allergy can be determined by determination of specific IgE from blood, skin prick tests and application test. It should be noted that the results do not have an absolute meaning in diagnosis and do not guarantee that a positive result means an allergy to a specific cause and a negative test means its absence.


The most reliable is the elimination and provocation test. The suspected foodstuff identified on the basis of the survey and tests is excluded from the menu for 2-4 weeks (until the symptoms disappear). During the provocation, the same food is eaten again in small quantities. If the symptoms reappear, the food that caused the disturbance has been found. During the elimination and provocation test, a food diary must be kept, in which the food eaten at the time of day, skin symptoms and their strength, the reaction of other organ systems, illnesses, vaccinations and the use of medications are noted. If there is a risk of a very strong reaction, provocations are performed in the hospital or abandoned altogether (5).


Diagnosing allergies:


  • Food diary;

  • Allergological skin tests or prick tests. Tests are performed with natural food extracts that are introduced into the skin with a gentle prick;

  • Patch tests. The test provides additional information in the case of chronic skin inflammation and is performed when  the development of food allergy is not related to IgE - antibodies;

  • Blood tests - the tests determine the content of IgE antibodies in the blood;

  • Elimination and provocation tests. Suspect foods are excluded from the menu for a while, and then the allergen is reintroduced and the body's reaction is monitored. At the same time, a food diary is kept;

  • Blind tests. The subject is given food, but he does not know what it is - so psychological reactions are excluded



There are actually no simple and accurate tests to test for delayed hypersensitivity reactions, often called food intolerances. The most effective way is for some time to suspecteliminating foods from the menu and then reintroducing them, while keeping a food diary (1,12).





Used sources:



1. Gamlin, Linda, “Handbook of Allergy”, 2009

2. Grün-Ots, Ille "When food makes a child sick", 2009

3.Hoffman, Roland article  "Is your diet making you sick?", 2013

4. Julge, Kaja, "Our Everyday Allergy", brochure of the Estonian Allergy Association "Food and Allergy".

5. Lehtmets, Ama, "Food allergy and atopic dermatitis", Estonian Allergy Association brochure "Food and Allergy".

6. Plado, Silvi, "Cross-allergy", Estonian Allergy Association brochure "Food and Allergy".

7. Vasar, Maire dr. and Julge, Kaja dr., "Food and allergy", 2004






13. British Dietetic Association fact sheet:



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