I agree with Trillian.. it'll be the P220. I'm a chef for a child care centre and allergins and sensitivities are always a concern.

We've recently started a 3yo boy who has an issue with P220, so no vegemite for him..and no processed cheese. Like Kraft Singles or Bega Slices. Stick to the proper cheese, if you want sliced, try Mainland.

Marmite doesn't have P220 in it, so that is what I offer as an alternative to this particular boy.

IMO rather than subjecting your boy to the painful allergin tests, try an elimination diet of exluding the P220 and P282 (found in bread). Most bakery fresh bread is P282 free.

Also, most children grow out of their allergies by the time they are 5. I would hold off for a while before trying him again on the P220.

Hope this helps.