Worldwide, respiratory diseases have a significant impact on morbidity and mortality of individuals.Tobacco, lifestyle and certain allergens such as dust mites play an important role in the prevalence and morbidity of these diseases. Scientific literature indicates that sensitization to allergens and respiratory diseases (asthma, rhinitis, chronic obstructive pulmonary disease) are closely linked. Moreover, smoking has an effect on allergen sensitivity.

To make a diagnosis of allergic sensitization, skin tests are performed in the patient. One of the methods used is the technique of "prick test". In practice, a drop of purified allergen extract is placed on the patient's skin (arms or back). A little dosis of the product is then injected in the epidermis. If fifteen minutes later, there is an edematous reaction, its diameter is measured in millimeters. From 4 mm, it is considered that the patient is sensitized to the tested foods or allergens.This technique is painless and convenient to patients of all ages, including newborns or conversely very aged patients.

This is a retrospective study based on the encoding and statistical analysis of data collected in patients followed within the Immuno-Allergology Service of the CHU Brugmann Hospital, who received an allergy assessment between 01/01/2015 and 31/12/2015. The allergens tested include: dermatophagoides pteronyssinus (DEPT), dermatophagoides farinae (DPF), blomia, cat, dog, cockroach, orchardgrass, timothy grass, alder, hazel,birch, olive tree, cypress, ash, latex, aspergillus, alternaria, cladosporium, peanut, hazel.

At least 1400 files will be analyzed.

Patients will be distributed in six age groups.The results of the allergen skin tests will be encoded as the edema diameter. The allergenicity score (mean of the skin reactivities for each allergen) will be compared between each age groups. The impact of tabagism, gender, BMI and residential area on the allergic reactivity will also be assessed in the overall population and within each age group.

The main objective is to evaluate the effect of age on the skin test positivity. The secondary objective is to highlight the environmental factors that have an impact on allergic diseases.

Inclusion Criteria:

• All patients followed within the Immuno-Allergology Service of the CHU Brugmann Hospital
• Who received an allergy assessment between 01/01/2015 and 31/12/2015. The allergens tested include: dermatophagoides pteronyssinus (DEPT), dermatophagoides farinae (DPF), blomia, cat, dog, cockroach, orchardgrass, timothy grass, alder, hazel,birch, olive tree, cypress, ash, latex, aspergillus, alternaria, cladosporium, peanut, hazel.

Exclusion Criteria:

• Negative histamine patients

Patients followed within the Immuno-Allergology Service of the CHU Brugmann Hospital, who received an allergy assessment between 01/01/2015 and 31/12/2015.