Hives after skin contact with vomit

[Sengi]

Dd 10 months is allergic to cows milk and egg. I first noticed a reaction on skin contact after introducing milk in cereal at 6 months. I have never noticed any sickness, diarrhoea etc which I would put down to allergy. We have started the milk ladder under advice from a dietician, and she has had 1 malted milk biscuit most days for the past few weeks with no noticeable effects. I am not excluding dairy from my diet, again as advised by paediatrician & dietician.
After her bf first thing this morning, she brought a bit of milk back up which went on her skin, and came up in hives. She still regularly possets/vomits a small amount, and I've never seen this skin reaction to it before. Has anybody else come across this? She has also had some diarrhoea the past few days, which I had put down to teething since she's had 3 come through in the past week.