Substance capable of causing an allergic reaction by activating the immune system and triggering allergic inflammatory conditions.


Protein produced by the immune system capable of neutralising or destroying foreign bodies such as bacteria, viruses, parasites, etc. Also known as immunoglobulin.


Medication used to treat allergy symptoms.


Chronic disease of the respiratory system characterised by inflammation, cough, difficulty breathing, inspiratory whistles, increase of mucosity.


Inflammatory disease of the membrane that covers the eye (whitish part of the eye).


Medication with anti-inflammatory function. Used to treat allergy symptoms. May lead to serious adverse effects in long-term treatment such as alterations in bone growth in children or osteoporosis, among others.


Exaggerated, abnormal response of the immune system to substances that normally do not cause harm in non-allergic individuals.

Ig E

Antibody or class E immunoglobulin directly involved in the allergic reaction. Produced in excess in allergic patients. It can be measured in blood and specifically for the allergen responsible for the allergy.

Ig G

Antibody or class G immunoglobulin that is produced as a protection against infections or immunotherapy.


Body's protective response against aggression or presence of microorganisms that cause damage to tissues.

Specific immunotherapy

The only treatment for allergy that treats the cause. Based on administration in increasing and cumulative doses of the allergen which causes the allergy to produce an immunological and clinical tolerance.

Subcutaneous immunotherapy

Immunotherapy administered via injection under the superficial layers of the skin.

Sublingual immunotherapy

Immunotherapy administered via drops or tablets under the tongue.


Cells needed for the proper functioning of the immune system or body's defences. They are in charge of fighting infections and diseases.

Mast cells

Cells that synthesize and store histamine (chemical substance released during an allergic reaction) and which are mostly found in the tissues of the body. In an allergic response, the allergen stimulates the release of antibodies, which bind to the mast cells, releasing histamine.

Prick test

Skin test to determine if a person is allergic to a given substance. To perform it, the doctor places a drop of the substance to be analysed on the person's forearm or back, prinking the skin with a needle, thus allowing a small amount of it to penetrate the skin. If the person is allergic to the substance a red wheal will appear in approximately 15 minutes.

Allergic rhinitis

Disease of allergic origin characterised by the inflammation of the nasal mucosa.


Initial exposure to the allergen, which induces a specific response that the immune system memorises and may give rise to an allergic reaction with subsequent exposures to the same allergen.


Decrease in the effect of the dose of a drug or given substance after repeat administration, which requires an increase in dose to obtain the same effect.

Aetiological treatment

Treatment that modifies the natural course of the allergic disease. According to the WHO (World Health Organization), the only allergy treatments available with these characteristics are immuotherapies or anti-allergy vaccines.

Symptomatic treatment

Allergy treatment with medications such as antihistamines, corticosteroids, leukotriene antagonists, etc.