**6. Prevention of food allergy**

#### **6.1 Breastfeeding for the prevention of food allergy**

Breast milk is the gold standard for protective nutrients fed to newborn infants, and present clinical evidence supports the strong protective effect of breast milk against age-related infectious gastroenteritis [44]. An important function of early breastfeeding is its antiinflammatory effect on the immature, excessive inflammatory response in newborns.

Food Allergy in Atopic Dermatitis 245

[49]. Avoidance of highly allergenic foods beyond 4–6 months might not be effective in preventing the development of food allergy in most children, and the effect of specific early introduction of allergenic foods was being investigated. Significantly, delaying the introduction of solid foods until 4 to 6 months of age in infants at a high risk for atopic

**6.3 Elimination of hyperallergenic foods from the diet of prenatal or breastfeeding** 

mother's immune system protects the fetus from foods ingested by the mother.

plays a role in preventing food allergy by correcting the Th1/Th2 imbalance [21].

mild AD should be treated early to prevent repeated allergic responses.

**6.6 IL-10 for the prevention of food sensitization** 

with subsequent allergen exposures [53].

**6.7 Skin hydration** 

Opinions about a mother's diet during breast feeding differ. Whether a mother should follow an elimination diet for hyperallergenic foods to prevent food allergy remains a matter of debate [2]. From prenatal development studies, however, there is no evidence to support the assumption that an elimination diet can prevent food allergy because the

The development of food allergy is related to Th2-deviant immune status in the sensitization phase of AD [9]. Although IFN- has tolerogenic effects on pre-existing food allergy, the development or prevention of a food allergy is primarily associated with sensitization. IFN-

The diagnosis of food allergy and subsequent elimination diet of all possible allergenic foods is important to prevent further sensitization from repetitive allergy provocation. Repetitive allergy provocation and the resultant further Th2-polarization make patients more likely to develop additional allergies [2]. Sensitization to more food allergens, as well as aeroallergens, can occur with repeated allergy flares. It follows that allergy provocation by known allergens should be avoided to prevent further sensitization. For this reason, AD should be evaluated for repetitive allergy provocation and not simply the severity of AD. Furthermore, patients with

Helminths induce generation of IL-10 in the gut and prevent sensitization to foods in mice [50]. Promotion of an IL-10-rich environment in the gut was investigated for its role in preventing or even treating food allergies. The prevention of food allergies by administering either an IL-10-secreting *Lactococcus lactis* [51] or an avirulant *Salmonella typhimurium* strain that promotes IL-10 secretion in the gut [52] was demonstrated. In this study, transiently expanded IL-10-secreting T cell populations played an important role in keeping the allergen-specific effector T cell responses in check. From these results, it was possible to explain how skin exposure to high doses of allergens led to a decreased immune response

Physical injury leads to a Th2-deviant status in the local skin and resultant allergic status (Fig. 2) [54]. These changes result in sensitization to simultaneously exposed allergens as described above. Dryness is one of the main causes of itching. For all aspects of AD symptoms,

skin hydration is very important to prevent further sensitization through the skin.

disease appears to reduce the incidence of AD [11].

**6.4 Correction of Th1/Th2 imbalance** 

**6.5 Prevention of allergy provocation** 

**mothers** 

Several components of breast milk, including transforming growth factor (TGF)-beta, interleukin (IL)-10, erythropoietin, and lactoferrin, can reduce the inflammatory response to stimuli in the newborn intestine. Although, historically, there has been widespread support for the concept that breast-feeding is protective against atopic disease in general, breastfeeding could facilitate food allergies in certain cases by allowing transfer of the allergens from the mother's diet through breast milk. Exclusive breastfeeding for 4 months should be recommended to prevent atopic disease; however, there is no evidence to support the protective effect of exclusive breastfeeding beyond this period. Mixed feeding should be encouraged until 6 months of age.

#### **6.2 Delayed introduction to solid foods to prevent the development of food allergy**

An additional question regarding food allergy and AD is whether delaying the introduction of solid foods to infants at a high risk for AD can delay or prevent the development of AD. The most recent clinical report states that exclusive breast feeding for 4 to 6 months for infants who are at a high risk for AD (i.e., positive family history) can help prevent or delay AD; furthermore, cow's milk should not be introduced until 2 years of age in order to prevent allergy [11]. No convincing evidence exists to delay the introduction of any solid food beyond 4 to 6 months of age. In contrast, dairy products are recommended to be introduced at 12 months; hen's egg at 24 months; and peanuts, tree nuts, fish, and seafood at 36 months.

Attempts to avert the development of food allergy through primary prevention strategies such as early restriction of dietary allergens and modified timing of complementary solid food introduction to infants have proven to be frustrating and possibly counter-productive. Early dietary restriction of peanuts is recommended to avoid sensitization [34]. However, early consumption of food proteins and subsequent oral tolerance induction in infants and children may be a key element in preventing the development of food allergies. In another study, neither the diversity nor the timing of introduction of complementary foods had any association with development of eczema. The most recent recommendations for high-risk infants do not endorse restriction of maternal diet during pregnancy and lactation or restriction of allergenic foods in infants after 4–6 months of age.

Elimination of highly allergic foods is plausible to prevent the development of food allergy [34]. Concerning the timing of solid food introduction, a delay does not seem to prevent the development of food allergy, but it may enhance sensitization to some foods. Introducing solid food at 4–6 months might result in the lowest allergy risk and the recommended duration of exclusive breast feeding and age of introduction of solids were confirmed to be 6 months [46]. Exclusive breastfeeding for at least 4 months for infants at a high risk of developing atopic disease but no current convincing evidence that delaying solid food introduction, including fish, eggs, and foods containing peanut protein, beyond 4–6 months of age had a significant protective effect on the development of atopic disease [47]. In contrast, early introduction of peanuts during infancy, rather than avoidance, was reported to prevent the development of peanut allergy [48]. Their data might be a good example of oral immune tolerance in a human model.

In contrast, some reports have suggested that delaying the introduction of hyperallergenic solid foods during weaning is not effective in preventing the development of food allergy. A new concept about the timing of weaning and the introduction of solid foods was suggested

Several components of breast milk, including transforming growth factor (TGF)-beta, interleukin (IL)-10, erythropoietin, and lactoferrin, can reduce the inflammatory response to stimuli in the newborn intestine. Although, historically, there has been widespread support for the concept that breast-feeding is protective against atopic disease in general, breastfeeding could facilitate food allergies in certain cases by allowing transfer of the allergens from the mother's diet through breast milk. Exclusive breastfeeding for 4 months should be recommended to prevent atopic disease; however, there is no evidence to support the protective effect of exclusive breastfeeding beyond this period. Mixed feeding should be

**6.2 Delayed introduction to solid foods to prevent the development of food allergy**  An additional question regarding food allergy and AD is whether delaying the introduction of solid foods to infants at a high risk for AD can delay or prevent the development of AD. The most recent clinical report states that exclusive breast feeding for 4 to 6 months for infants who are at a high risk for AD (i.e., positive family history) can help prevent or delay AD; furthermore, cow's milk should not be introduced until 2 years of age in order to prevent allergy [11]. No convincing evidence exists to delay the introduction of any solid food beyond 4 to 6 months of age. In contrast, dairy products are recommended to be introduced at 12 months; hen's egg at 24 months; and peanuts, tree

Attempts to avert the development of food allergy through primary prevention strategies such as early restriction of dietary allergens and modified timing of complementary solid food introduction to infants have proven to be frustrating and possibly counter-productive. Early dietary restriction of peanuts is recommended to avoid sensitization [34]. However, early consumption of food proteins and subsequent oral tolerance induction in infants and children may be a key element in preventing the development of food allergies. In another study, neither the diversity nor the timing of introduction of complementary foods had any association with development of eczema. The most recent recommendations for high-risk infants do not endorse restriction of maternal diet during pregnancy and lactation or

Elimination of highly allergic foods is plausible to prevent the development of food allergy [34]. Concerning the timing of solid food introduction, a delay does not seem to prevent the development of food allergy, but it may enhance sensitization to some foods. Introducing solid food at 4–6 months might result in the lowest allergy risk and the recommended duration of exclusive breast feeding and age of introduction of solids were confirmed to be 6 months [46]. Exclusive breastfeeding for at least 4 months for infants at a high risk of developing atopic disease but no current convincing evidence that delaying solid food introduction, including fish, eggs, and foods containing peanut protein, beyond 4–6 months of age had a significant protective effect on the development of atopic disease [47]. In contrast, early introduction of peanuts during infancy, rather than avoidance, was reported to prevent the development of peanut allergy [48]. Their data might be a good example of

In contrast, some reports have suggested that delaying the introduction of hyperallergenic solid foods during weaning is not effective in preventing the development of food allergy. A new concept about the timing of weaning and the introduction of solid foods was suggested

encouraged until 6 months of age.

nuts, fish, and seafood at 36 months.

oral immune tolerance in a human model.

restriction of allergenic foods in infants after 4–6 months of age.

[49]. Avoidance of highly allergenic foods beyond 4–6 months might not be effective in preventing the development of food allergy in most children, and the effect of specific early introduction of allergenic foods was being investigated. Significantly, delaying the introduction of solid foods until 4 to 6 months of age in infants at a high risk for atopic disease appears to reduce the incidence of AD [11].

#### **6.3 Elimination of hyperallergenic foods from the diet of prenatal or breastfeeding mothers**

Opinions about a mother's diet during breast feeding differ. Whether a mother should follow an elimination diet for hyperallergenic foods to prevent food allergy remains a matter of debate [2]. From prenatal development studies, however, there is no evidence to support the assumption that an elimination diet can prevent food allergy because the mother's immune system protects the fetus from foods ingested by the mother.
