Preventing Food Allergies
Preventing food allergies may be possible, especially if your child is at high risk of having a food allergy, including already having an allergy to another food or formula, having other family members with food allergies, or having other 'allergic' type conditions or family members with these conditions, such as eczema, allergic rhinitis (hayfever) and/or asthma.
Most importantly, breastfeed and avoid supplementing with infant formula or offering solids for at least the first six months of your child's life. If you are not breastfeeding or need to supplement, then consider using a hypoallergenic infant formula such as Nutramigen or Alimentum (soy formulas and goat's milk may not be good alternatives, because many infants that are allergic to cow's milk may also be allergic to soy). If you are breastfeeding, then you should avoid peanuts and tree nuts in your own diet, and consider avoiding milk, fish and eggs too (discuss this with your doctor, as avoiding too many foods may cause poor nutrition).
If your child is at high risk of having food allergies, you should also delay offering solids until he is at least six months old (and continue breastfeeding), and begin with an iron fortified infant cereal. It is best to start with rice and oat cereals and introduce wheat cereals later. Next you can introduce vegetables, but avoid legumes (foods in the bean and pea family) at first, and then non-citrus fruits and fruit juices. Meat and protein foods can be added once your child is 8-9 months old.
Foods to avoid until your infant is at least a year old include cow's milk, citrus fruits and juices, and wheat and egg whites until he is two. Also, avoid giving peanuts (as smooth peanut butter), fish and shellfish until your child is at least three years old. Whole peanuts and tree nuts should be avoided until your child is four because of the choke hazard.
When you do introduce new foods, do so slowly and only give one new food every four to five days. This way, if your child does have a reaction or allergy, then you will know which food caused it and you will be able to avoid giving it again.
Source: http://www.keepkidshealthy.com/infant/startingsolids.html