Who is affected by food allergies?

Anyone. While food allergy most commonly develops in young children, anyone can develop food allergies. Adults can develop new food allergies after years of ingesting a food without reaction.
Developed World. People in the 3rd world nations and developing countries do not appear to be effected by food allergies. This is a phenomenon of industrialized society as we are seeing the numbers of people effected by food allergies grow daily and this is not just a product of better surveillance. Lots of theories as to why this is but no hard proof yet. Stay tuned.
Anyone. While anyone can develop a food allergy at any time, children are more likely to develop a food allergy than an adult. However, in children food allergies are sometimes temporary and will be outgrown. But in adults, food allergies tend to be more permanent. Some food allergies, such as those to shellfish and nuts tend to be permanent across all ages.