Peanuts make the top of the big 8 list of food allergies but there really is no definitive answer to this question. Much depends on your family history. If you or anyone in your child's family has a food allergy or allergic type disorder (like asthma or eczema) or if your child has had a food allergy in the past, then you should wait to introduce peanuts and peanut butter. How long? According to the American Academy of Pediatrics, you should wait until your child is 3 years old.
In addition, mothers with any history of a peanut allergy in the family should avoid peanuts and peanut butter in the third trimester of pregnancy and for as long as they are nursing their children.
If there is none of the above in you or your child's history, however, then peanut butter can be a healthy addition to the diet when your child turns 1 year old.
Information from: http://babyparenting.about.com/od/nutritionandfeeding/f/peanutbutter.htm
at 1:18 PM on Sep. 9, 2009