Diagnosis

Faced with signs suggestive of allergy, it is essential to consult an allergy specialist so they can identify the allergen(s) in question and make sure there is a causal link with the onset of symptoms.

This detection may lead to the introduction of treatment by allergen immunotherapy (or desensitization), the only treatment currently capable of altering the natural course of the allergic disease.  

The different stages of allergic rhinitis diagnosis

The interview is the first stage in diagnosis. The aim is to confirm the existence of an allergic state and establish a preliminary list of allergens which may be causing the observed symptoms.

The main areas covered are:
- History of the symptoms (how long ago they first appeared, what they are like and when they occur, any triggering factors already identified)
- Family history of allergy (any close relative who is allergic) or in the patient's own history (allergy during childhood)
- The patient's general environment (living and working conditions as well as climate)
- Details about lifestyle and habitats (home, workplace, pets, eating habits)
- Activities (occupation, pastimes)

It may take more than one consultation to gather all of the information required.

As well as a general examination (weight, blood pressure, etc.), the specialist examines in detail those organs in which allergic symptoms commonly manifest themselves (the skin, lungs, nose and bronchi). This allows the allergist to assess the impact of the allergy and indicates possible further tests that might fall outside the allergic field (pulmonary function tests in asthma).

After the interview and physical examination, a list of allergens that might be responsible is compiled in order to narrow down the field for skin testing.

The point of a skin test is to try to reproduce on a very small scale on the patient's skin the allergic reaction in its "immediate hypersensitivity" form (the allergic reaction appears immediately after contact with the allergen involved).

What does skin testing entail?

A drop of the suspected allergen is placed on the forearm or back, and then a tiny puncture is made in the skin at the centre of the drop to allow the allergen to penetrate the dermis and provoke the allergic reaction

The results can be read after 20 minutes: a hypersensitivity reaction results in redness of the skin resembling a mosquito bite with oedema (swelling) and itching.

The severity of the reaction is evaluated compared with the reaction caused by a "control" substance (a "control" substance causes a reaction in all individuals without exception and makes it possible to learn the degree of severity with which the body of the patient reacts).

This technique is fast, painless, reproducible over time and well-tolerated, even by very young children. It is the most commonly used method.

When the prick tests cannot be interpreted or are negative although the symptoms persist, the allergist may call on a blood test. Identification of the specific IgE antibodies will enable the allergen in question to be identified.

After reading of the results, the specialist passes on invaluable advice:

- avoidance of allergens if possible
- prescription of medication (antihistamines, bronchodilators, corticosteroids) depending on the severity of the disease and which will act immediately to relieve the symptoms
- treatment by allergen immunotherapy when the indication so lends itself as of 5 years of age.

When introduced to treatment early on, allergenic immunotherapy can alter the natural course of the allergic disease¹.