ROLL'YN-OMA: an Observational Study in Patients Treated by Omlyclo®, an Omalizumab Biosimilar

Who May Qualify: - Be an adult (aged 18 years or older at the time of inclusion) receiving specialist care and diagnosed with one of the following conditions: Severe asthma, Chronic Spontaneous Urticaria - Have been treated for at least 6 months prior to inclusion with the reference omalizumab for the relevant condition (Severe asthma or Chronic Spontaneous Urticaria). - Have been stable for at least 3 months according to the prescribing physician, with the disease controlled or in clinical remission based on the disease-specific activity score: Severe asthma: ≤ 1 course of oral corticosteroids per year related to disease worsening, without hospitalization, and ACQ \< 1.5 and FEV1 ≥ 80% of the patient's most recent values/ Chronic Spontaneous Urticaria : UCT ≥ 12 - For whom the specialist physician has decided to switch to OMLYCLO® (biosimilar developed and marketed by Celltrion) on the day of patient inclusion (shared medical decision independent of the study). - Be able to start treatment within a maximum of 60 days following inclusion. - Have an email address. - Have a mobile phone number. - Be able to understand and complete questionnaires in French. - Not object to participating in the study. - Be affiliated with a French Social Security scheme or be a beneficiary of such a scheme Who Should NOT Join This Trial: - Patients under guardianship or trusteeship, or otherwise deprived of liberty. - Pregnant women or women of childbearing potential with a desire to become pregnant during treatment with OMLYCLO®. - Patients who, at the time of inclusion, are participating in a clinical trial or another clinical study that prohibits simultaneous participation in other studies. - Contraindication to the study products. Always talk to your doctor about whether this trial is right for you.