Clinical Research Directory

Inclusion Criteria: * Positive case history of immediate allergic reaction(s) to walnut * Presence of specific IgE to walnut assessed by either SPT (≥ 3 mm mean wheal diameter) or serum IgE determination (≥ 0.35 kU/L) by ImmunoCAP (ThermoFisher Scientific, Uppsala, Sweden) in the previous 12 months. * Informed Consent as documented by signature Exclusion Criteria: * Known hypersensitivity or allergy to Omeprazole or other PPI * Known hypersensitivity or allergy to mannitol * Drugs not allowed during the study due to proved interaction with Omeprazole: Digoxin, Clopidogrel, Methotrexate, Antiretroviral drugs, Diazepam, Cilostazol, Phenytoin, Warfarin (R-Warfarin) and other Vitamin K antagonists, Phenytoin, Tacrolimus, Drugs suppressing or inducing CYP2C19 or CYP3A4 such as Clarithromycin, Voriconazol, Rifampicin and Hypericum * Drugs not allowed due to interference with the food challenge (or shortest interval between last treatment and food challenge) * corticosteroids systemically (2 weeks) * antihistamines (3 days) except hydroxizine (10 days) * ketotifen (2 weeks) * betablocking agents (1 day) * angiotensin converting enzyme (ACE) inhibitors (2 days) * tricyclic antidepressants (5 days) * omalizumab (2 months) * immunosuppressive treatments * Women who are pregnant or breast feeding * Intention to become pregnant during the course of the study * Lack of safe contraception, defined as: female participants of childbearing potential, not using and not willing to continue using a medically reliable method of contraception for the entire study duration, such as oral, injectable, or implantable contraceptives, or intrauterine contraceptive devices * Female participants who are surgically sterilised / hysterectomised or post-menopausal for longer than 2 years are not considered as being of child bearing potential. * Uncontrolled asthma, FEV1 \<70% predicted value * Acute allergic disease (transient exclusion criterium) * Chronic urticaria * Mastocytosis, elevated tryptase/mast clonal disorders * A contraindication to adrenaline (i.e. ischaemic heart disease, poor controlled hypertension or cardiac arrhythmia) * Other clinically significant concomitant disease states (major organic or infectious diseases, e.g., renal failure, hepatic dysfunction, cardiovascular disease, acute febrile infection, psychiatric disorders) that can affect patient's safety or can make the implementation of the protocol or the interpretation of results difficult. * Known or suspected non-compliance, drug or alcohol abuse, * Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant. * Participation in another study with investigational drug within the 30 days preceding and during the present study.