Venoms from stinging or biting animals would need to be injected in
order to cause a problem.  As most of them would surely be proteins,
they probably would not survive in the baby's stomach even if they were
small enough to get into the mother's milk.

Antivenoms are antibodies made by injecting small amounts of venom into
animals which then make antibodies and the antibodies are concentrated
from their blood.  Since they are usually IgG or IgM (unlikely), they
would not get into the milk in any significant amounts.  But even if
they did, so?

By the way, there is no reason the mother cannot use hydrocortisone
cream and/or antihistamines for her itching.

Jack Newman, MD, FRCPC