What is allergy?
Allergies are an abnormal reaction by the body, which responds in an exaggerated way upon entering into contact with substances from the exterior, to which most other individuals do not normally react. These substances are called allergens.
An allergic reaction is therefore an exaggerated defensive response or hypersensitivity of the immune system, occurring in genetically predisposed individuals, who we call atopic or allergic.It is unclear why affected individuals are allergic to one substance versus another (allergens), such as pollen, mites, foods, dander, medicines or industrial products.
The symptoms associated with allergy (rhinitis, conjunctivitis, asthma, skin reactions, etc.), depend on the type of allergen and route of entrance
Causes of allergy
The substances responsible for allergic reactions are called allergens.
These are substances that are recognized as “foreign” by the immune systems of allergy sufferers and which, in contrast, cause no problems among non-allergic persons.
How is it diagnosed?
The patient’s medical history is an important factor in diagnosing the allergy. The patient should tell the specialist about the environmental conditions in which they live (home, work, contact with animals, etc.), symptom trigger factors, family history of allergy, etc.
Allergies specialists use various methods to diagnose allergies.
The methods most used in diagnosing the cause of the allergy are:
- Skin test
These tests aim to reproduce the allergic inflammatory response in the skin. The test allergens are selected according to the patient’s medical history and the prevalence of sensitization of the environment in which they live.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 droplet has been deposited. If an allergic reaction develops as a result in the form of a wheal, the patient is considered to react to the allergen, and the latter may be responsible for certain symptoms.
- Determination of specific IgE
A special blood test that detects immunoglobulin E (antibodies that intervene in the allergic reaction) specific to the allergen or allergens suspected of causing the symptoms.
- Contact Dermatitis
It is an inflammation of the skin that is caused by direct contact with an irritant. Contact dermatitis is characterised by itching in the areas of irritation and skin rash. Subsequently, reddening occurs with small vesicles that tend to dry up, forming a scab, which finally flakes off. When the eczema persists, small cracks occur in the skin and it swells. The most frequent cause are irritants. These may be chemical compounds such as soaps, detergents or solvents; metals such as nickel, chrome, cobalt or mercury, among others; medications applied topically, such as local anaesthesias; dyes and hair products, cosmetics, clothing materials, adhesives or surgical tape, perfumes, fragrances, rubber materials, industrial plastics, etc.
How is diagnosed? Diagnosis is based on direct clinical assessment of the area affected, and determination of the history of exposure to an irritant. In cases of doubt, epicutaneous patch tests may be conducted to specify the cause of the allergen responsible for the allergic reaction.
- Patch test
Patch testing attempts to reproduce the allergic reaction on the normal skin on the upper back of the patient. The patches are applied and subsequently removed after 48 hours. Reactions are read after 72 – 96 hours and often, again at 7 days after removal. The diagnostic value of patch testing depends upon the choice of test substance, the vehicle, the concentration, results interpretation and patient counseling. Patch tests are comprised of materials that occur in the home, work and/or recreational environment.