Food intolerances do not involve the immune system. Instead, they can occur for a variety of reasons such as an enzyme deficiency as in lactose intolerance, the inability to digest milk sugar due to the lack of an enzyme called lactase. Another adverse reaction is chemical in origin and is called a pharmacologic food reaction. An example would be caffeine. Some people are more 'sensitive' to caffeine and can drink only one cup of coffee without getting the jitters, while others can drink several cups and not be affected.
Babies are more likely to suffer from food allergies.
Most food allergies are outgrown by the age of three, perhaps because of a maturing immune system. In fact, seventy to eighty percent of infants with a milk allergy will be able to tolerate milk by 4 years of age. For children with a family history of allergies one way to help delay the onset and reduce the severity of a food allergy is to nurse the baby and take the necessary precautions to eliminate from the diet the most potent allergens, like milk, egg, fish, and nuts. Another effective tactic in preventing food allergies is to delay the introduction of certain foods that contain common allergens. Wait until at least six months to offer dairy products or egg yolk, eight months for wheat, citrus fruits and cooked tomatoes, and ten months for fish, shellfish, peanuts, corn, berries, raw tomatoes and chocolate.