Heredity may cause a predisposition to have allergies of any type, and repeated exposure to allergens starts sensitizing those who are susceptible. Some experts believe that, rarely, a specific allergy can be passed on from parent to child. Several studies have indicated that exclusive breast-feeding, especially with maternal avoidance of major food allergens, may deter some food allergies in infants and young children. (Smoking during pregnancy can also result in the increased possibility that the baby will have allergies.) Most patients who have true food allergies have other types of allergies, such as dust or pollen, and children with both food allergies and asthma are at increased risk for more severe reactions.