J.B.
Hi S.!
I've used antihistamines even while breastfeeding. I'm not sure which I was using at the time, but it was either Zyrtec or Clarinex. Did you use the medicine when you were pregnant? If so, then breastfeeding while taking the medicine won't be any different than taking it when you were pregnant. My doctor said that the benefits from the medicine outweighed the slight risk to the baby. Good luck!
J.