Studies have shown the risk of peanut allergy can be cut by more than 80% by early exposure.
The National Institute of Allergy and Infectious Diseases said the new guidance was "an important step forward".
However, young children should not eat whole peanuts, because of the risk of choking.
Allergy levels are soaring in the US and have more than quadrupled since 2008.
It is a pattern replicated across much of the Western world as well as parts of Asia and Africa.