How do i know when is a good time to give my 16 month old peanut butter?

Look out for choking: In healthy kids delaying foods beyond 6m doesn't reduce allergies (& may even increase them). However, i recommend avoiding very allergic foods when kids are on antibiotics or have diarrhea or a tummy illness. With peanut butter, keep in mind that it's thick, sticky texture makes it a real choking risk: so small amounts (perhaps with something ekse) with adult present.

Any time : If she has never had an allergy to it before, it should be ok to try already. Try a very small portion first just to be on the safe side, increasing the amount in following day(s) if no reaction to the small amount. If you are asking because she did have a reaction in the past, then do not give it until your doctor says it is ok... And when u do, it is usually done at the allergist office.