There is a pregnancy condition called PUPPP -- itchy hives. I don't have a reference to the study on hand, but it is known that most women who suffer from PUPP

There is a pregnancy condition called PUPPP -- itchy hives. I don't have a reference to the study on hand, but it is known that most women who suffer from PUPPP give birth to boys, and that male DNA is present in the hives. One theory about it goes that male DNA is a skin irritant.