The goal of this observational study is to evaluate the role of IgE proteoforms in healthy volunteers and in patients with type I allergy, patients with chronic spontaneous urticaria, patients with a recent history of anaphylaxis, patients with mastocytosis, patients with hereditary alpha tryptasemia, patients with X-linked agammaglobulinemia (XLA), and patients undergoing desensitization for venom or medication allergy.

Inclusion Criteria:

• CSU and type I allergic diseases (including anaphylaxis and desensitization), atopic dermatitis, mastocytosis, XLA and HaT (informed consent, age: any available adult subject, gender: any available subject, clinical phenotype and specific information about the allergy (e.g. severity, medication, medical history, laboratory testing)
• Healthy controls (informed consent, age matched to the allergic patients, gender matched to the allergic patients, patient-reported symptoms related to allergy to aeroallergens, food, drugs, hymenoptera venom, CSU)

Exclusion Criteria:

• Absence of informed consent
• Age < 18 years old

Patients with type I allergy (including medication allergy, venom allergy, food allergy, allergic rhinitis), patients with chronic spontaneous urticaria (with or without omalizumab), patients with a recent history of anaphylaxis in whom serial sampling can be performed, patients undergoing desensitization for venom allergy, patients undergoing desensitization for medication allergy, patients with mastocytosis, patients with hereditary alpha tryptasemia, patients with X-linked agammaglobulinemia (XLA), healthy controls