Twenty children/adolescents, 12 to 22 years, with severe peanut allergy will be treated with omalizumab and the effect evaluated with CD-sens. If the CD-sens is negative a peanut challenge will be performed. If the challenge is negative the OIT will start: 1, 2, 4, 8 g peanuts/day in two-week intervals followed by a maintenance dose of 10 g peanuts/day while continuing treatment with omalizumab. If the CD-sens is still negative the withdrawal of omalizumab will start by halving the dose in several steps.