Yes DS1 was allergic to soya as well. The milk and egg allergies got worse but the soya one got slowly better. When he was around 4 we would buy him a 4-pack of soya yoghurts but he never had them all because his skin would get rougher and rougher. Now he eats 2 at a sitting.
slowburner have you tried Osteocare Liquid? It's not always easy to find but my DCs adored it, and I am about to start giving it to DS2 as like DD although he isn't allergic, because he wasn't allowed any milk for the first year of his life he now won't touch it.