This study will assess the clinical potency of several exposure levels of QGE031 in decreasing the sensitivity against peanut allergen.

Main Inclusion Criteria:

• Diagnosis of acute peanut allergy as manifested by urticaria, angioedema, gastro-intestinal or respiratory tract symptoms, with acute onset of symptoms after ingestion (up to 2 hours).
• Positive peanut food challenge at baseline, i.e., have objective allergic events at a level of 300mg (not cumulative) or below of peanut protein but not to the placebo test.

Main Exclusion Criteria:

• Prior exposure to any monoclonal antibody treatment
• Asthma patients on maintenance long acting beta-agonists
• Use of systemic corticosteroids
• Concomitant use of beta blockers, ACE inhibitors, tiotropium or ipratropium, antidepressants, oral beta-agonists
• Use of immunosuppressants within 6 months of visit 1 Other protocol-defined inclusion/exclusion criteria may appy