Um, according to my research three is the recommended age for families with allergy. This is government advice via the food standards authority. Five is the recommended minimum age to give whole nuts - but that's because of the choking risk and not allergy. Of course, it would be fine to never give a child peanuts or peanut butter, but that isn't the official advice. And of course, I am very glad that my son doesn't have a peanut allergy. It must be very difficult and very frightening.
This is from Babycentre - but you'll find the same stuff on the food standards website.
When is it safe to feed my baby...?
Nuts
It's true that you shouldn't give whole nuts to children who are under five years old, because of the risk of choking. But nut butters and finely chopped nuts are fine for babies and children who do not have a family history of allergies.
Serious allergies to nuts and nut products and some seeds do affect less than one per cent of the population. Your baby may be at higher risk if you, your baby's father, brothers or sisters have certain allergic conditions such as hayfever, asthma and/or eczema.
If your baby is in this higher-risk group, avoid eating peanuts and peanut products while breastfeeding and during the introduction of solid foods. Until the child is at least three years old, peanuts and peanut products should be avoided.
If you think your child might be allergic to peanuts, contact your GP who can arrange for your baby to see an allergy specialist.
If you do not have a history of allergy in the family, you can give ground nuts and nut spreads, including peanut butter, from six months old. Read our article on is it safe for my baby to eat nuts? for more information.