Food allergies are diagnosed in about 8% of toddlers tested. The incidence in adults is much less than this (at most, 4%). This means that by the time a toddler reaches adult life they have a good chance of growing out of their allergy.
Even children with significant food allergy to the likes of egg and cow’s milk can grow out of it in due course. Peanut allergy tends to be more persistent but it is still possible to lose this one too.