Patients

Allergic diseases are among the most common chronic diseases. Experts estimate that 30%-40% of the population worldwide suffer from one or more allergic diseases.

At present, there are an estimated 10 million people with allergies in Spain.

Main allergens that cause allergies

There is a certain amount of age-related variability. For example, food allergies and dermatitis are more common in the paediatric population, and as children grow they experience the onset of different respiratory problems: Rhinitis and Asthma. This process has come to be called the“Allergic March”.

The peak incidence of allergies is at 14-24 years of age.

In Spain, the most common food allergies are to cow’s milk, eggs, fish and nuts. In many children, food allergies are transitory and disappear when patients grow.

As regards inhaled allergens, there are so-called indoor allergens, which are typically mites; the animal dander ; and, to a lesser extent, fungi and outdoor allergens, which are basically pollen and fungal spores.

In general, individuals develop allergies to the allergens to which they are most exposed. This is particularly notable in pollen. Pollen allergies depend on the pollen present in the geographic area of patients with allergies.

Why the prevalence of allergies is increasing

In general, there are two essential factors in developing an allergic disease: genetic load and environmental exposure.

In recent years, allergic diseases have had a considerable increase that cannot be explained by genetic changes, which occur very slowly. Therefore, environmental factors would be responsible for developing allergic diseases.

Other reasons are:

The increase in environmental pollution is another potential reason for the increase in allergic diseases, since some pollutants such as diesel emissions are believed to increase the potential for sensitisation.
The Lifestylealso plays a role, since the population is being exposed for longer periods of time at home to contaminants such as cigarette smoke and allergens such as mites.
Non-exposure to infectious agents and antibiotic treatment. The immune system fails to mature due to a lack of stimulation, and instead allergic and autoimmune diseases develop.

Any natural substance may cause allergic diseases through inhalation, ingestion or contact. Such a substance is called an allergen.

But what substances cause allergies?

Any natural substance may cause allergies in the body. Such a substance is called an allergen, and the main agents that cause the allergic process are:

MITES: These are microscopic "bugs" that live in homes and are found in household dust and on the surfaces of objects. They feed on our dead cells and any type of environmental proteins, and cause allergic reactions in a high percentage of the population.

POLLEN: These are microscopic grains found in the flowers of plants. They spread through the air and cause allergic reactions when inhaled. The most common are:

-Grass Pollen
-Plant Pollen
-Tree Pollen

FUNGI: These are a group of living beings that develop on any surface and reproduce by means of spores, which mainly spread by the wind and which cause approximately 10% of cases of asthma of allergic origin.

FOODS: Any food or condiment may end up triggering an allergic reaction. The most common foods are: Milk, eggs, fish, seafood, nuts and fruits.

HYMENOPTERA VENOM: The main causes of allergies due to stings are bees and wasps. These may cause reactions such as swelling and itching and may trigger serious reactions and in some cases anaphylaxis.

ANIMAL DANDER:The substances present in the fur of certain animals may end up causing allergies. Cats, dogs and horses are among the most allergenic animals.

DRUGS: Any drug can cause an allergy. Taking drugs suspected of causing allergies must be avoided, and the specialist must be informed of the supposed reaction triggered to start an allergological study.

Pollen, mites, fungi, foods, hymenoptera venoms, dander and drugs are substances that may cause an allergic reaction.

There are different allergic diseases depending on where the inflammatory reaction occurs.

Rhinitis, conjunctivitis, asthma, atopic dermatitis, eczema and urticaria, are the most common allergic diseases.

If the reaction is on the skin, it may be Atopic Dermatitis, also called eczema. This involves reddened, itchy skin and tends to appear in childhood. It may also be Urticaria, characterised by the appearance of welts on the skin, which are also itchy. Sometimes, it may be accompanied by swelling of the lips and eyelids. This is called Angio-oedema.

If the reaction is on the skin, it is Rhinitis, which features itching, nasal obstruction, postnasal drip and sneezing. In most cases, it also affects the eyes and causes Conjunctivitis with itching, reddening and watering of the eyes. Rhinitis that appears exclusively in spring or summer is called seasonal rhinitis as opposed to perennial rhinitis, whose symptoms occur throughout the year.

When an allergic reaction occurs in the bronchi, these constrict, which hinders the passage of air and produces a characteristic sound, called wheezing. At the same time, the patient experiences trouble breathing (dyspnoea), coughing and chest tightness. These are symptoms of Allergic Asthma. Most of the time, patients with asthma also have rhinitis.

When patients ingest a food to which they have a food allergy, an inflammatory reaction occurs in their gastrointestinal system: Gastroenteritis, which may lead to the onset of abdominal pain, vomiting and diarrhoea. At the same timeUrticariamay appear as a result of absorbing the food in question.

There are particularly serious cases in which there is a massive release of inflammatory substances throughout the body and the individual develops an all-over reaction called ANAPHYLAXIS.

Symptoms of anaphylaxis include: a feeling of heat, reddening, tingling in the mouth and urticaria with itching. Other symptoms may be a feeling of dizziness, dyspnoea, throat tightness, pain/cramps and/or vomiting and diarrhoea.

Anaphylactic Shockoccurs if anaphylaxis compromises the heart and circulatory system and leads to very low blood pressure with loss of consciousness and shock.

Anaphylaxis is particularly common in people with allergies to bee and wasp venom when they are stung by these insects. It is also more common in people with drug and latex allergies.

The most characteristic symptoms of allergic reactions are: Nasal itching, watering of the eyes, conjunctivitis, sneezing, postnasal drip and nasal obstruction, coughing, difficulty breathing, reddened skin, and swelling.

Allergic diseases result from the immune system reacting to a substance that it considers foreign. This system plays a role in defence against microorganisms and potentially disease-causing substances.

When there is an allergy, the immune system acts against a normally harmless substance, considers it foreign and mounts an inflammatory reaction against it with certain special characteristics.

The substance that triggers the reaction is normally a protein and is called an allergen. The body manufactures another protein, called an antibody, against it. Antibodies belong to a special group of proteins called immunoglobulins.

The antibodies responsible for neutralising allergens belong to a class of immunoglobulins, specifically Immunoglobulin E, also called IgE.

When the body first comes into contact with the allergen, it manufactures IgE against it. This is called sensitisation. From this point on, any subsequent exposure to the allergen is generally going to cause symptoms characteristic of allergic reactions.

The IgE formed in the process of sensitisation travels throughout the body and eventually binds to certain cells: mast cellsand basophils. When there is further contact with the allergen, these cells burst and release a number of inflammation-mediating substances. The best known of these is histamine, responsible for the inflammatory allergic reaction, whose symptoms may be rhinitis, conjunctivitis, urticaria, asthma and others.

Each type of IgE targets a specific allergen, i.e. is specific, such that a person who only manufactures IgE against cat fur is not going to be allergic to other substances. These patients are said to be monosensitised, since they are only sensitised to a single allergen.

By contrast, some people manufacture IgE against multiple allergens; they are called polysensitised..

The process by which one person becomes allergic and another does not is unknown. However, it is known that people with a family history of allergic diseases are more prone to suffering from them.

In an allergic disease, the immune system mounts an exaggerated inflammatory reaction when it comes into contact with a substance that the body considers foreign.

Patients

Main allergens that cause allergies

Why the prevalence of allergies is increasing

But what substances cause allergies?

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