Could first drink of cows milk cause bad nappy rash?

[mandymac]

Hope 'allergies' is the right place for this.
DD 21 months has had either breastmilk or follow on milk until yesterday, but never just plain old cows milk (I delayed due to family history of allergies). So yesterday, she had a drink of cows milk for the first time and today for just about the first time ever, she has really bad nappy rash, which seems to have come up about 10 mins after a pooey nappy (sorry if tmi! ). She has had yogurt, cheese, butter etc with no ill effects.
Could it be the cows milk?

[moondog]

Doubt it.
Cows milk is a much less buggered about with product than follow on milk.