Does a vegan diet give young children a higher risk of allergy?

No, not as far as we know. We have no studies that compare vegan and non-vegan children directly, but the trials of early introduction of allergens give a fairly clear picture. The only thing a vegan child misses out on is egg.

Well-cooked egg a couple of times a week from 4-6 months probably lowers the risk of egg allergy12. A child who doesn't eat egg doesn't get that effect. It makes no difference as long as the child doesn't eat egg, but it is worth knowing if the child starts eating it later.

Peanuts, on the other hand, are plant food and fit right in. In a British trial of infants with severe eczema or egg allergy, 13.7% of those who avoided peanuts had developed peanut allergy at 5 years, against 1.9% of those who ate peanuts from infancy34. In another British trial the children had about two teaspoons of peanut butter a week, and there too, peanut allergy was less common5. Give them in a form that suits the child's age6.

Cow's milk doesn't seem to play the same role. In the British trial, early cow's milk had no effect on milk allergy5, and the European allergy experts make no recommendation for or against regular infant formula after the first week of life7. Soy-based infant formula can be used from birth, and wanting to feed the child a vegan diet is one of the recognised reasons to choose it2.

What actually needs attention is not allergy but nutrition. Vegan toddlers are at high risk of getting too little B12 and at risk of getting too little calcium8. Calcium matters for bones: Finnish teenagers who had milk allergy as infants had lower bone density9. Young children can grow and develop normally on a vegan diet with the right supplements, but it takes help from a dietitian and a doctor following their growth10.