The prevalence of allergic diseases (atopic dermatitis, asthma, rhinitis, conjunctivitis and food allergy) has increased dramatically in industrialized countries over the last 20-30 years.

Allergic diseases are present especially in children and young adults, but all age groups are affected, with variations across countries and age. To propose new therapies, the investigators must first understand the physiopathology.

Since their discovery the regulatory T cells have continued to be the subject of work to understand their role in maintaining immune homeostasis in the human body but also their involvement in autoimmune diseases, inflammatory diseases, transplants of solid organs or fluids and allergic diseases.

It was identified two broad classes of regulatory T cells:

• T cells = natural regulators acquisition of a phenotype and a regulatory function right out of the thymus ( CD25 + / CD127 + low / FoxP3 +).
• T cells induced regulators = acquisition of a phenotype and a regulatory function on the periphery depending on the cytokine micro-environment.

Phenotypic characterization of these is less obvious and even more so than during the last ten years several induced regulatory T cell populations have been described ( eg, Tr1 ).

A new subpopulation of T cells induced in patients with inflammatory bowel disease recently identified have a particular phenotype as bearing the CD4 and CD8 double marking with a regulatory phenotype.

These regulatory T cells are also induced a specific of a commensal intestinal bacterium (Faecalibacterium prausnitzii).

Regarding allergies, it has been widely demonstrated a relationship between changes of the intestinal microbiota and the occurrence of allergic diseases.

The investigators would therefore propose a cross-sectional study, single-center, controlled, single blinded to study the role of T cells called double positive induced regulators DP8 to compare the frequency and the regulatory function of specific DP8 of Faecalibacterium prausnitzii in atopic dermatitis, asthma and allergic rhinitis compared to control samples.

The primary endpoint will be the highlight of a quantitative reduction of double positive T cells (CD4 + / CD8 +) the specific F prausnitzii peripheral blood in patients with allergic asthma, allergic rhinitis and atopic dermatitis compared to samples from a control sample collection made available by the laboratory BIOFORTIS® located near Nantes University of Nantes.

Inclusion Criteria:

• non smoker
• BMI <30kg/m²
• No contraindication to prick-test
• Inform consent signed for genetics
• belong to a social security scheme
• patients with allergic rhinitis or atopic dermatitis or with allergic asthma

Exclusion Criteria:

• major or major incapable protected
• antimicrobial treatment (antibiotic, antifungal or antiviral)
• in contact with an MDR bacteria
• has received or is receiving specific immunotherapy
• History of cancer of the hematopoietic system
• antecedent acquired immune deficiency with HIV
• congenital immunodeficiency
• inflammatory bowel disease
• autoimmune disease and / or inflammatory
• solid organ transplant or hematopoietic cells
• addict
• pregnant or of childbearing age without effective contraception
• failure of acute or chronic severe organ
• hardly speak French and / or difficult to understand French

Patients undergoing a consultation with an allergist at the University Hospital of Nantes or city firm under a monitoring or an initial consultation for atopic dermatitis, allergic asthma or allergic rhinitis.