The skin is innervated by a network of nociceptive sensory neurons (nociceptors) whose primary function is the transmission of pain and pruritus signals to the central nervous system. Their role in atopic dermatitis (AD), characterized by an exacerbated type 2 immune response, is only partially understood. Nevertheless, large amounts of neuropeptides, including substance P (SP), are found in the serum of patients, their level being correlated with the clinical severity of AD. Mast cells (MC) are part of the cells of the immune system residing in the skin. MCs have neuro-receptors of the Mas-related G protein-coupled receptors family (MRGPR) and in particular MRGPRX2 (the receptor for cationic molecules [including SP] for MCs) through which they could communicate in a privileged way. with the nociceptors. Preliminary data obtained in mice show that its mouse orthologue "MrgprB2" is absolutely necessary for the development of type 2 immunity and the pathological characteristics of a preclinical "DA-like" model (manuscript in preparation). The investigators therefore hypothesize that the activation of MCs expressing MRGPRX2 by nociceptors producing SP plays a key role in the development of type 2 inflammation in AD in humans.

Inclusion Criteria:

Criteria for the study population:

• Subject affiliated with a social security scheme or beneficiary of such a scheme;
• subject who has given written consent to participate in the study;
• Subject accepting a blood test to check for the absence of infectious diseases (HIV serologies, Hepatitis B, Hepatitis C) in the event of a blood exposure accident;
• Subject who did not apply emollient care products to the areas to be biopsied within 24 hours prior to the inclusion visit.
• Subject accepting biopsies

Criteria related to the pathology studied:

• Subject with atopic dermatitis according to UK Working Party criteria or Williams criteria with an IGA score ≥ 3 (group 1)
• Subject with atopic dermatitis according to UK Working party criteria or Williams criteria in the form of an atopic prurigo diagnosed by the dermatologist (group 2)

Criteria relating to control subjects: Subjects who had abdominoplasty and agreed to use their skin sample as part of Genoskin (Ministerial Approval # AC-2017-2897) (Group 3).

Criteria for treatment:

• Systemic treatments for AD (including phototherapy) or biotherapies interrupted at least 4 weeks before the inclusion visit;
• Topical treatments: topical corticosteroids and tacrolimus stopped on the biopsied area at least 7 days before the inclusion visit.

Exclusion Criteria:

• Criteria for the study population:

  • Solar exposure of biopsied areas planned during the study;
  • Subject having had exposure to solar radiation or artificial UV within 2 weeks before inclusion in biopsied areas.

Criteria related to the pathology studied:

• Chronic inflammatory dermatosis other than classical AD or atopic prurigo at sites to be harvested;
• Subject with a known history of allergy or intolerance to local anesthetics, local antiseptics to latex or plaster;
• Subject already having abnormalities of healing
• Subject with a recognized addiction to alcoholism or drug addiction;
• Subject having an inherited or acquired disease of hemostasis;
• Subject having a severe or acute chronic condition deemed by the investigator to be inconsistent with the trial;
• Subject with immunodeficiency clinically incompatible with the study.

Criteria for treatment:

• Any topical or systemic treatment of AD (including phototherapy) in progress
• Treatment likely to act on the haemostasis (example: anticoagulants, antiaggregating platelet ...) in the 4 weeks preceding the inclusion and during the study;
• General corticosteroids in the 4 weeks prior to the inclusion visit
• ongoing systemic treatment that may interfere with the healing process;
• Subject having undergone a physical treatment (radiotherapy, ...) on the area to be biopsied, during the last 6 months.
• History of treatment or concomitant treatment that may interfere with the completion of the study according to the opinion of the investigator.

Criteria for regulation:

• Subject unable to comply with protocol requirements;
• Subject in linguistic or psychic incapacity to sign informed consent;
• Subject being in a period of exclusion during which he can not participate in any other biomedical research;
• Subject participating in another biomedical research;
• Subject deprived of liberty by judicial or administrative decision, under guardianship, curatorship or safeguard of justice;
• Person with severely impaired physical and / or psychological health who, according to the investigator, may affect participation in the study.