Formula to cows milk transition

[HLM1989]

My son is 1 next week, when we saw the HV last week she said could transition him to cows milk. He is breastfed but has always had a bottle of formula at bedtime. He eats very well, cows milk in his porridge every morning, yoghurts, cheese etc.
We started 8 days ago with swapping 1oz of formula for 1oz cows milk (he’s fussy how he has his formula & only one specific brand) so wanted to transition him gradually rather than completely changing him over. We gave each oz a few days for him to get used to the taste and now he’s on 3oz cows milk & the rest formula. However for the last 4 days or so he’s had big loose smelly stools. Not in any pain or discomfort, eating fine, happy as usual. We usually give prune in his porridge but I’ll stop that for now but wondering if people have any advice? Should I continue slowly weaning him onto the cows milk or go right back to full formula? I can’t see how he would have a cows milk intolerance but I guess it can’t be ruled out

I could be mild CMPA as the formula will be more hydrolysed or it just ciukd be a coincidence. The CMPA could explain his fussiness over the formula though. Could you cite back to 2 floz tonight and see if he improves?

@TinyMouseTheatre thank you for your reply. He did have hand foot and mouth last week so he’s been a bit all over the place so at first I thought maybe that could be contributing.
I’ll dial back to 2oz and keep at it for a little while longer - see how he is. No milk/dairy intolerances in any of mine or my husbands family nor our 4 year old so never imagined our baby having any intolerance 🥴

My LO was the same. He was tongue tied and never managed to successfully breastfeed and then had a bit of a nightmare with formulas. He was on goats milk formula for 9 months but was fine with dairy during weaning. When we switched to cows milk he had looser huge poos too, and his nappies did…and still do cause my eyes to water. They stink. He transitioned quite quickly and was absolutely fine though, I think it was just a bit of an adjustment onto the full fat milk.

If they have an allergy I would imagine it would have been noticeable by now if you eat dairy and having cows milk formula and dairy. As long as little one is happy I’d continue transitioning onto cows milk if it was me.

@Keepsmiling2948 - thank you, this is reassuring that your little one was similar! Yes the eye watering smell is something else, I checked on him at 1am this morning and his room stank so had to change him. Haven’t had to do a nighttime nappy in a long time 😂 also went to a baby class this morning and he did one there too, no baby changing facilities so had to change him in the corner of the hall and I felt so bad for everyone else as it stank.
I will probably keep on slowly transitioning him, maybe a bit slower than I’d of liked & hopefully he’ll adjust 🤞🏼