An allergic reaction is an overreaction of the immune system to a substance that does not cause a reaction in most people. The most common allergic reactions are to animal dander, dust, pollen, medications and food allergies.
Allergic reactions are common, it is estimated that in industrialized countries around a third of the population suffers from some type of allergy, they are one of the most common chronic conditions in the world. Generally, allergies are accompanied by mild symptoms, causing sneezing, red and itchy eyes, runny nose, irritation and itchy skin. In some cases they can be serious and even fatal.
In today’s article we are going to detail What is an allergic reaction and what mechanisms cause it? its causes and the most frequent symptoms of this very common pathology.
As we mentioned in the introduction, allergies are an exaggerated reaction of the immune system. Many cells and organs collaborate with each other to protect our body, this is what we know as the immune system. The immune system is capable of reacting specifically against a wide variety of foreign substances and invaders, known as antigens, this specificity of the immune response occurs thanks to specialized proteins capable of fighting foreigners, the antibodies. The immune system can produce a varied number of different antibodies for each antigen. Furthermore, the immune system has memory, this means that it can easily and quickly recognize an antigen, against which it had already generated a response, when it re-enters the body.
Normally, the immune system identifies and reacts to non-dangerous foreign substances (pollen, animal dander, dust, food, etc.) without causing any type of damage to the body. In allergy, the immune system reacts aggressively against foreign substances, damaging cells and tissues; these reactions They are grouped under the name of hypersensitivity reactions These reactions can be caused by both antibodies and the cells of our immune system. Allergy is an immediate hypersensitivity reaction, this means that the reaction occurs quickly, within seconds or minutes after exposure to the substance.
Allergy symptoms can occur in any organ of the body, but they are more common in areas that have greater contact with external agents Therefore, inflammation of the skin, nasal passages, respiratory tract or digestive system is more common.
The severity of allergies varies depending on the person, normally they present as a mild form, showing: skin irritation, sneezing, runny nose and itchy and red eyes. But in some allergic reactions, called anaphylactic reactions, the symptoms are life-threatening.
Why do allergic reactions occur?
As we have already seen, the immune system is capable of detecting foreign substances (called “antigens”) and eliminating them. But in addition, the immune system has memory, so that it can easily and quickly recognize an antigen against which it had already generated a response, when it re-enters the body.
Immune memory occurs through lymphocytes and antibodies The immune system has special cells, lymphocytes. We have billions of lymphocytes in our body, and each lymphocyte is capable of fighting a specific “invader.” If we have not been exposed to the foreign substance before, our body does not have many specific lymphocytes to fight it. But in the process of battle, the lymphocytes that are capable of fighting the “invader” multiply to combat and eliminate it.
Lymphocytes fight against the offending agent by manufacturing antibodies. Antibodies are specialized proteins that locate and immobilize antigens. Making an analogy, the lymphocyte would be the policeman and the antibody would be the baton.
Thus, in the second exposure to the same infectious agent, our immune system will have antibodies to fight the invader so that we will be able to eliminate it before it can cause more serious damage.
This memory also explains why vaccines serve to protect us against many diseases. A vaccine introduces the antigen into the body in such a small amount that the disease does not develop, but it allows the body to make antibodies to protect itself from future attacks.
Common allergic reactions, such as certain types of asthma and hives, are related to the IgE antibody (immunoglobulin E).
The antibody, IgE, binds to a type of white blood cell (defense cells) called a mast cell, which is found in tissues. When the previously sensitized person is re-exposed to the allergen, the mast cells, with IgE (antibodies) on their surface, release chemicals, such as histamine, prostaglandins and leukotrienes.
These substances produce a chain reaction of reactions that affects various organs and tissues, which become irritated or damaged with varying degrees of intensity. This is what we know as an allergic reaction.
Causes
Both genetic and environmental factors are involved in the development of allergies. The genetic origin factor of allergies is believed because mutations are common in people with allergies, and Allergies tend to be shared between members of the same family
Environmental factors can also increase the risk of developing allergies. The repeated exposure to foreign substances diet, and pollutants (such as tobacco smoke and gases) ultimately increase the risk of suffering from some type of allergy.
The allergic reaction can have different causes:
Symptoms
Symptoms caused by an allergic reaction vary depending on exposure to the allergen: type, time, amount and mode of contact But also, the reaction of the immune system.
As we already saw in the mechanisms section, a first exposure causes a mild inflammatory reaction and the production of IgE antibodies. Each reaction will cause our body to manufacture more antibodies and there will be more mast cells with these on their surface, releasing an increasing amount of chemicals. . Even very limited exposure can trigger a serious reaction even leading to anaphylactic shock.
Allergy symptoms vary depending on the type of allergy, the most common being the following.
Food allergy presents:
Tingling in the mouth
Swelling of the lips, tongue, face, or throat
Urticaria
Anaphylaxis
Insect bite allergy presents:
An area of large swelling (edema) at the site of the bite
Itching or hives all over the body
Cough and breathing difficulties
Anaphylaxis
A drug allergy presents:
Wheezing (whistling, squeaky sound during breathing)
Urticaria
Skin itch
Acne
swelling in the face
Anaphylaxis
Allergic rhinitis (hay fever) presents:
sneezing
Itchy eyes, nose and/or mouth
Runny nose, stuffy nose
Watery, irritated, or swollen eyes (conjunctivitis)
Anaphylactic shock is a medical emergency, as it puts a person’s life at risk It is a reaction where the body tissues narrow, including those in the throat, making it difficult to breathe. There is also a drop in blood pressure, which can cause blood to not reach all organs. These two symptoms are life-threatening.
At the slightest suspicion of anaphylactic shock, action must be taken immediately calling 112 to report the condition and seek medical attention as soon as possible.
Related article: “Anaphylaxis (anaphylaxis): symptoms, causes and treatment”
Diagnosis
The main objective of the diagnosis is identify the allergen responsible for the reaction For this, a medical evaluation is carried out, where an attempt is made to determine through questions when the allergy began and its frequency.
For example, the time of year in the case of seasonal allergies, or determining what types of foods trigger the allergy in the case of food allergies.
Screening is the main diagnostic tool, as blood tests and skin testing tend to give quite a few false positives and negatives.
The skin test involves exposing the patient to a small amount of an allergen protein candidate. If the patient is allergic, characteristic hives usually appear on the skin.
The blood test will look for amount of the patient’s IgE antibodies in the bloodstream It is not a sufficiently specific test.
Treatment
Today, the best way to treat and prevent allergies is to abstain, that is, to avoid exposure to the substance that causes them
To combat the symptoms caused by the allergic reaction, medications such as antihistamines or corticosteroids are usually used, but they are a temporary solution, since they act only on the symptoms and not on the origin of the allergy.
In some cases immunotherapy can be used, generally consists of vaccines, based on injections of purified allergen extracts. These vaccines are typically administered over a period of two years. The goal is to desensitize the patient to the allergen. This type of treatment is used especially in allergies in which it is very difficult or impossible to avoid contact with the allergen, such as aeroallergens, mainly pollens and mites.
Prevention
Prevention varies depending on the allergy, but some general recommended measures include:
Remove and avoid the allergen as much as possible. Avoid the forest or green areas in spring for pollen, change sheets frequently and vacuum for dust allergies.
To write a diary. If the allergen has not yet been determined, a diary can help identify it.
Minimize exposure to certain irritating products (tobacco, humidity, strong odors)
Wear a medical alert bracelet. The use of this bracelet is recommended if you have suffered a serious reaction.
If you have a severe allergy, you should carry an emergency epinephrine injection with you
We hope that with today’s article you have understood the mechanism by which allergies occur and their consequences.
