Hi Pandora. My DS2 has a cows milk protein and soya intolerance so have learnt about all this the hard way...
How have you fed DS2 up to now? Has he had any dairy or cow's milk based formula up to this point?
An allergy is a reaction to something recognised by the body as foreign and mediated by IgE antibody. It can be checked for on blood or skin prick tests for common allergens. It's a worry because you can get quite severe reactions (think hives, swelling of face and throat, tightness of chest etc) up to anaphylaxis. If your child has a true allergy then you may need to carry an Epipen to give them if they have a bad reaction.
An intolerance is a bit of a vague term. It can be used to mean an immune reaction not mediated by IgE (so negative on allergy tests) and is generally delayed by hours-days rather than immediate, and milder than an allergic reaction. Symptoms can include gastrointestinal ones (tummy pain, constipation or diarrhoea, mucus or blood in poo, weight gain issues) skin rashes, eczema, or respiratory signs (cough, wheeze, congestion). It can also mean lacking enough of an enzyme so unable to digest something (e.g. lactose intolerance) or a reaction to foods where they act like a drug (e.g. foods containing salicylates). Also widely used by the general population for any food that they think may disagree with them!
There's also a wide degree of severity. My son used to react to dairy/soy via breastmilk so I had to be dairy/soy free, but this is no longer the case and at 21m he can now tolerate a bit of "processed" dairy or soy e.g skim milk powder in a biscuit or soya flour in bread, but not yoghurt/cheese/milk. There will be a tolerance level somewhere for each individual, and most children with a milk protein intolerance will outgrow it by the time they start school.
I'd be interested to hear what dairy your LO has been ok with so far (if any) and if you need dairy-free suggestions I can probably help. jen x
Messtins, part-time vet, rest-of-the-time Mum to D 10/06 and M 05/10