Pepti Jnr to Karicare HA for challenge?

Hi there all!

My DS, who is 2.5 years old, has been on a prescription formula since he was 12 months old. Prior to this I breastfed him on an elimination diet etc.etc. He has dairy and soy allergies. The prescription formula he was on was Pepti Jnr which is an extensively hydrolysed formula (the casein protein is broken down). Anyway, as a challenge, the paediatrician suggested that I give one of the supermarket HA formulas a go, and he has just tried some today. He has tried Karicare HA (not the reflux one). It is partially hydrolysed. Same idea, but not as broken down. The other suggestion was Pediasure. But it contains soy oil and is again partially hydrolysed, and my DS has already reacted to this one. The formula has been suggested as the first port of call in challenging him, as he is a small boy, whose allergies have contributed to his small size, and formulas have high calories in them, more so than cow's milk, and this is what he needs. He needs full fat and high calories. He has Rice Milk as a fun drink as a snack, but it is not a milk replacement as such. It is too low in fat for his age.

So has anyone been in a similar boat and how did your toddler handle changing from a prescription formula to a supermarket HA one? Did it take about 3 days for any problems to become evident? What were your experiences? I was not sure whether to put this in Bottlefeeding section or allergies & Intolerances section. Hope someone has a response anyway :)

Thank you in advance :)

Well, he's just had diarrhoea, so it looks like it may be a no go.