6 months. There is no good evidence that delaying nuts -- or any food -- beyond 4 to 6 months old reduces allergies. In fact, the delay may increase the risk food allergies. However, unless crushed, etc., nuts and nutbutters are shapes or textures that are easy to choke on. Avoid any choking hazards. Also, I do suggest avoiding commonly allergic foods when a child is on antibiotics or has a GI illness.
12-36 months. You should wait until 12 months to introduce nuts to your child. You may even wait until 24-36 months of age if there is a family history of food allergies or if your child has a food sensitivity.
4 months. Older rules recommended holding off on nuts and other highly allergenic foods until older, but new research supports giving nut products when infants are developmentally ready to eat foods, if no one in the family is allergic. Don't give foods babies will choke on, but using nut products is ok in making foods. Pregnant and breastfeeding moms can also eat nuts in most instances under the new rules.