Personally I wouldn’t say that’s a CMPA rash, both my kids have a milk allergy. My little boy got diagnosed at 6 weeks and his symptoms were projectile vomiting, screaming in pain, constipated for over a week, eczema and blisters on his bum. My little girl who’s 10 weeks now has been on neocate since she was 3 weeks old her symptoms were never keeping her bottle down and I mean she would projectile vomit the whole lot out it was horrific first night home we got sent to the hospital because she turned blue from choking on her vomit, not gaining weight properly she was in first size for 6 weeks, congestion, constipation then diarrhoea and a lot of mucus in her nappies it was pretty much full of it, rashes covering her face neck back and chest, and a horrific nappy rash that had the doctors even stumped because nothing worked. Your little boy could have reflux?? But it also could be reflux triggered by a cows milk allergy
I’d say more heat rash or skin to skin irritation but can’t say for sure obviously xx
Is he sick a lot? As my first used to get rashes around his ears and neck a lot from the irritation of the sick as that’s where it falls. If it isn’t fungal the drs will treat it as dry skin (eczema) x
Following as my little boy has very similar symptoms!