Allergens are common substances, normally innocuous to most people, but which are recognised as "foreign" by the immune systems of allergy sufferers. The most common allergens are pollen, house dust mites, animal epithelia, foods, medicines, fungi and bee and wasp stings.
Allergens cause sneezing, coughing, watery eyes and other symptoms according to the route of entrance and the type of allergen in those who have allergies.

People with allergies are born that way, as some people are born with brown hair or green eyes.  However, each person has a different way of reacting to the same allergens. Pollen, dust or other allergens may cause congestion and nasal obstruction, coughing, sneezing and even breathlessness or difficulty breathing.

The substances responsible for allergic reactions are called allergens.

These are substances that are recognised as "foreign" by theimmune systems of allergy sufferers and which, in contrast, causeno problems among non-allergic persons.

More than 25% of the population in industrialized countries suffers some type of IgE mediated allergy.

For reasons that are unclear, allergy is extremely common, and it has been predicted that the number of allergies will have doubled in ten years. Recent studies indicate that atmospheric pollution is one of the main causes behind the increase in individuals allergic to pollen, especially in big cities. Specialists also suggest other factors such as the increase in tobacco consumption or the lack of exposure to germs during infancy (hygienist theory supporting vaccination), which have also been decisive in the increase in allergic patients.

Studies also suggest that the causative factors are associated with the Western lifestyle, as a majority of time is spent in enclosed spaces, the moisture from air-conditioning favours the growth of mould and mites, and more people have pets.

The immune system of that person responds by producing large quantity of antibodies known as IgE. The exposure to the allergen will cause the release of chemical mediators (histamine) which produce the symptoms typical of an allergic reaction, such as watery eyes, eye irritation, reddening of the eyes (conjunctivitis), sneezing, nasal congestion, nasal irritation, nasal secretion (rhinitis), coughing, breathlessness, wheezing in the chest (asthma).

People can be allergic to many things, but the most common causes are pollen, house dust mites, fungi, epithelia (from pets), medicines, some types of food and some products for professional use such as latex.

To keep an allergy under control you need to:

• Know that you are allergic. Your allergy specialist will help you diagnose this.
• Limit the quantity of allergens in your environment by taking simple measures and follow appropriate recommendations for prevention.
• Follow the treatment recommended by your specialist. Follow medication instructions where necessary. Your doctor will work with you to decide on the most suitable medication and in what situations it is required.

The two main methods used in allergy diagnosis are "in vivo" and "in vitro" tests.

The "in vitro" method involves a blood test that detects immunoglobulin E (antibodies that intervene in the allergic reaction) specific to the allergen or allergens suspected of causing the allergy.

A drop of the suspect allergen is placed on the patient’s skin, and a lancet is used to prick the skin onto which the drop has been deposited. If an allergic reaction develops in the form of a wheal, the patient is considered to react to the allergen, and the latter may be responsible for certain symptoms. The intensity of the reaction is assessed by comparing the size of the wheal produced by the allergen with the size of the wheal produced by histamine, a "control" substance that causes a reaction in all individuals without exception.

The most common symptoms presented by a person with allergy are: nasal irritation with watery mucous, sneezing and eye irritation.

With a cold, the most frequent symptoms are irritation, sneezing and watery eyes. Mucous is watery and transparent. In addition, fever is usually present with colds.

To confirm that an allergic process is involved and to determine the allergen responsible for your discomfort you need to see a specialist.

Allergy can be hereditary. A genetic predisposition to allergies exists in infancy. If both parents suffer from allergies, the risk of suffering said allergy is more than 70% as opposed to 50% when only one of the parents suffers from allergy. However, the individual must have exposure to the causative factors in order to become sensitized. Symptoms may appear in the first years of life, although they most frequently appear after the age of 5 and rarely after the age of 60.

According to the World Health Organisation, immunotherapy or vaccination is the only treatment that can change the natural course of allergies and prevent the development of asthma in patients with allergic rhinitis. Most allergies have a high cure rate if measures are taken to avoid or reduce exposure to the allergen(s) and the appropriate specific treatment is followed.

Yes. It is predicted that allergies will have doubled in ten years. Recent studies indicate that atmospheric pollution is one of the main causes behind the increase in individuals allergic to pollen, especially in big cities.

Diesel particles in the polluted atmosphere have shown a clear relationship with allergies and with aggravation of cases of asthmatic patients. Specialists also indicate other factors such as the increase in tobacco consumption or the lack of exposure to germs during infancy, which have also been decisive in the increase in allergic patients.

Studies also suggest that the causative factors are associated with the Western lifestyle, as a majority of time is spent in enclosed spaces, the moisture from air-conditioning favours the growth of mould and mites, and more people have pets.

Yes. Allergic reactions are being seen that were previously rare. This is due to the introduction of new materials, previously not used, into daily life, such as nickel or latex.

Yes, although they typically appear in infancy or at around 20 years of age when the allergy presents greater virulence. It also depends on the type of allergy, as food allergies mostly affect children and occupational allergies are mostly seen in adults.

See an allergist to have a precise diagnosis of your allergy carried out, take preventative environmental control measures and follow the treatment appropriate for the type of allergy you have.

Once the cause of the allergy is known, there are various measures that can be taken to improve, relieve and/or prevent the allergy according to the allergen responsible.

If you are allergic and have symptoms every year, for example when spring arrives, see an allergist before the first symptoms appear. The doctor will thus be able to start you on an appropriate treatment, which will help you to prevent possible acute episodes or your allergy from becoming chronic.

See measures in Prevention and recommendations.