Taking antihistamines is the normal response to having hives. However, if you're breastfeeding, anything you ingest appears in your breastmilk. The "American Family Physician" in July 2001 suggests taking any antihistamine immediately after breastfeeding to minimize the concentration that is excreted when your baby next nurses. The Merck Manual further suggests that nursing mothers use an inhaled form of antihistamine whenever possible to further reduce concentrations. However, a May 2010 study published in "Canadian Family Physician" states that "all antihistamines are considered safe to use during breastfeeding, as minimal amounts are excreted in the breast milk and would not cause any adverse effects on a breastfeeding infant."
Speak with your pediatrician about the recommended approach given your baby's medical history.
Determine if the hives are caused by the presence of an allergen to which you have been exposed. If possible, minimize or remove contact with the allergen.
Treat the hives with a cold compress to minimize their itchiness.
Take an antihistamine with your pediatrician's approval. Use an inhaled antihistamine and take it immediately after nursing to best serve the dual purpose of healing your hives and minimizing your baby's exposure to the drug.