What is an allergic reaction?

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 frequent, 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 of the world. Allergies are usually accompanied by mild symptoms, including sneezing, red and itchy eyes, runny nose, skin irritation and itching. Sometimes 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.

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Description of the allergic reaction

As we mentioned in the introduction, allergy is an overreaction of the immune system. Many cells and organs collaborate with each other to protect our body, it is what we know as the immune system. The immune system is capable of reacting specifically against a wide variety of

substances and foreign invaders, which are known as antigens, this specificity of the immune response is due to specialized proteins capable of fighting foreigners, the antibodies. The immune system can produce a number of different antibodies for each antigen. In addition, the immune system has a 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 organism.

Normally, the immune system identifies and reacts to non-hazardous foreign substances (pollen, animal dander, dust, food, etc.) without causing any damage to the body. In allergy, the immune system reacts aggressively against foreign substances, damaging cells and tissues; these reactions are grouped under the name of hypersensitivity reactions. These reactions can be caused by both antibodies and 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 frequent 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 from person to person, they usually 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.

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Why do allergic reactions occur?

As we have already seen, the immune system is able to detect foreign substances (called “antigens”) and eliminate them. But in addition, the immune system has a memory, in such a way that it can easily and quickly recognize to an antigen against which it had already generated a response, when it re-enters the organism.

Immune memory occurs through lymphocytes and antibodies. The immune system has special cells, lymphocytes. We have trillions 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 fight and eliminate it.

The lymphocytes fight against the offending agent by making antibodies. Antibodies are specialized proteins that localize 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 develops, but 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 (the defense cells) called a mast cell., found in tissues. When the previously sensitized person is re-exposed to the allergen, the mast cells, with the IgE (antibodies) on their surface, release chemicals, such as histamine, prostaglandins and leukotrienes.

These substances produce a chain reaction that affects various organs and tissues, which are irritated or damaged with varying degrees of intensity. This is what we know as an allergic reaction.

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Causes

Both genetic and environmental factors are involved in the development of allergies. The genetic 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) increase the risk of suffering from some type of allergy in the long run.

The allergic reaction can originate from different causes:

• Exposure to tree or weed pollen is known as a seasonal allergy, since it is common in the spring.
• Exposure to other airborne allergens, such as pet dander and protein, dust mites, and mold.
• The intake of some foods, especially peanuts and other nuts, are also common allergic responses to wheat, soy, fish and shellfish.
• Insect stings, such as bee or wasp stings (as occurs in anaphylactic reactions).
• Taking medications, especially penicillin or antibiotics based on this substance.
• When touching certain materials or substances such as latex, allergic skin reactions can occur.

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Symptoms

Symptoms produced by an allergic reaction vary depending on the exposure to the allergen: type, time, amount and mode of contact. But also, from the reaction of the immune system.

As we have already seen 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 are more mast cells with these on their surface, releasing an increasing amount of chemicals. Even very limited exposure can trigger a serious reaction.even lead to anaphylactic shock.

The symptoms of allergies vary according to 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 shortness of breath
• Anaphylaxis

An allergy to a medicine presents:

• Wheezing (whistling, high-pitched sound during breathing)
• Urticaria
• Skin itch
• Acne
• swelling in the face
• Anaphylaxis

Allergic rhinitis (hay fever) presents:

• sneezing
• Itchy eyes, nose and/or mouth
• Snot, stuffy nose
• Watery, irritated, or swollen eyes (conjunctivitis)
• Eczema (atopic dermatitis) allergic skin disorder presents:
• Itch
• redness
• Flakes or flakes

What is an anaphylactic shock?

An anaphylactic shock is a medical emergency, since it puts the person's life at risk.. It is a reaction where the body tissues are narrowed including those of the throat, making it difficult to breathe. There is also a drop in blood pressure, which can cause blood not to reach all organs. These two symptoms are life-threatening.

At the slightest suspicion of anaphylactic shock, you must act immediately calling 112 to report the condition and seek medical attention as soon as possible.

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Diagnosis

The main goal of diagnosis is identify the allergen responsible for the reaction. For this, a medical evaluation is made, where it is tried 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 often give quite a few false positives and negatives.

The skin test consists of exposing the patient to a small amount of the protein of an allergen candidate. If the patient is allergic, characteristic welts 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 specific enough 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, 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 normally given over a two-year period. The goal is to desensitize the patient to the allergen. This type of treatment is used above all in allergies in which it is very difficult or impossible 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 are produced and their consequences.