I'm Dr. Clark and I'm happy that you have asked me to assist you with your child and hope that you can benefit from my many years of helping parents like you.
There is no problem with your wife taking NyQuil as very little, if any, of the antihistamine even crosses in breast milk and won't have any effects on your baby.
Did that answer your question and do you have any other concerns.
I'm standing by but chat will time us out and kick us off after 4 minutes. I'll watch for your return to chat.