Prevalence of food allergies varied among studies, particularly due to methodology on how to diagnose food allergies. Studies that used self-report food allergy had higher prevalence of food allergies compared to studies that used skin prick test (SPT) of food specific immunoglobulin E (sIgE) examination or food challenge [2-4].

The result of meta-analysis on prevalence food allergy showed that prevalence of self-reported food allergy was very high compared to objective measures. There were heterogeneity between studies regardless of type of assessment or food item considered, and in most analyses this persisted after age stratification. Self-reported prevalence of food allergy varied from 1.2% to 17% for milk, 0.2% to 7% for egg, 0% to 2% for peanuts and fish, 0% to 10% for shellfish, and 3% to 35% for any food. However, confirmed prevalence of food allergy varied only from nearly 0% for fish and shellfish, 0% to 3% for milk, 0% to 1.7% for egg, and 1% to 10.8% for any food [2].

Food allergy can affect skin (urticaria, angioedema, atopic dermatitis), gastrointestinal tract (oral allergy syndrome, vomiting, allergic eosinophilic esophagitis, diarrhea, proctocolitis), and respiratory tract (nasal congestion, rhinorrhea, sneezing, itching of the nose and throat, wheezing). Anaphylaxis is severe manifestation of food allergy and it is increasing in prevalence, especially for peanuts allergy [1, 4].

The prevalence of food allergy in individuals with moderate to severe atopic dermatitis was reported around 30% to 40%, and these patients have clinically significant IgE-mediated food allergy as assessed by combination of convincing symptoms, SPTs, sIgE levels, or oral food challenges [5] or a definite history of immediate reactions to food [6].

Indonesia does not have data on national prevalence of food allergy. However, in our clinic we found that from 42 atopic dermatitis patients in 2012, most of them were sensitized by white egg (31%), cow's milk (23.8%), chicken (23.8%), yolk egg (21.4%), nuts (21.4%), and wheat (21.4%) [7]. A different pattern was found in our clinic back in 2011, which found that most of our atopic dermatitis patient was sensitized with maize, followed by white egg, tuna, chicken, cow's milk, and peanuts [8]. Meanwhile, we also found 3% of our diarrhea patients were cow's milk allergy (CMA) [9].

Diagnosis of food allergy in children is very difficult, especially in Indonesia where a lot of food with different kinds of spices added. Therefore, a careful history taking and daily record are important before further investigation.

The wrong perception or unawareness of mother on food allergy also can make difficulty in food allergy diagnosis. Prawirohartono [10] in Yogyakarta, Indonesia found that among 114 of medium to highly educated mothers, there were still wrong perceptions about food allergy. From 114 mothers, 48.2% of them believed that food allergy cannot be inherited, egg causes furuncle (54.3%), breast milk causes atopic eczema (46.5%), and food allergy does not related to respiratory symptoms. There was a relationship between these perceptions and mothers' educational level. According to these mothers, most common allergic manifestation was skin manifestation. Egg, shrimp, fish, and shellfish were types of animal foods which were recognized as major food allergen, while peanut, soy, banana, rice and vegetables were recognized as the major causes of food allergy among non animal products [10]. The variety of food composition, combined with other food additive, food color, preservative and spices in Indonesian food also make difficulty in food allergy diagnosis.

Consensus on the diagnosis and management of food allergy and allergy to cow's milk is made by Allergy Immunology, Nutrition and Metabolic Diseases, and Gastrohepatology Working Group of Indonesian Pediatrics Society (Ikatan Dokter Anak Indonesia) to prevent misdiagnosis and mismanagement of food allergy [11]. Before we made this consensus, many food allergy diagnoses was based only on history taking and excessive dietary restrictions by doctors that will surely disrupt child growth and development.

The diagnosis of food allergy in Indonesia based on careful history taking, physical examination, daily diet records, and SPT or sIgE as a guide to conduct elimination and provocation test (Fig. 1). Interpretation of SPT or sIgE should be done carefully, because positive results of SPT or sIgE only indicate sensitization and it does not always related to clinical symptoms. Provocation test is conducted in an open challenge methods because it is difficult technically to perform provocation test with double-blind placebo-control for children in our settings [11]. Safri et al. [12] found that only 67% subjects with positive results on cow's milk SPT had positive cow's milk challenge, while only 64% subjects with positive cow's milk IgE had positive cow's milk challenge. However, in this study definition of positive specific IgE for cow's milk was more than 0.4 kUA/L, which was lower than suggested predictive value for cow's milk IgE that correlate to cow's milk challenge in other review (Table 1) [13].

Management of food allergy is strict avoidance of food allergen. Substitute the allergen with other food, which is comparable for its nutrition value in order to prevent malnutrition. In breastfed babies, they can continue breastfeeding with food allergen elimination in maternal diet. Many studies tried to evaluate whether immunotherapy and pharmacotherapy, such as anti-IgE or anti-cytokine, will be effective for food allergy. Education about the diseases, natural history of food allergy, treatment including prevention of accidental ingestion or exposure, how to read label should be given to the parents or patients [1, 3, 13].

Diagnosis of CMA based on history taking and confirmed by elimination-provocation test. sIgE or SPT for cow's milk protein can be used to support the diagnosis. There are some differences in the management of CMA among different countries reflecting general and local needs and vision (Table 2).

In Indonesia, management of CMA in exclusively breast-fed infants is continuing breastfeeding and mother should avoid cow's milk formula and its products. Management of CMA in formula fed infants is based on severity of the disease. Extensively hydrolyzed formula should be given for infants with mild to moderate symptoms, while amino acid should be given for infants with severe symptoms. These special formulas should be given for minimum 6 months (Fig. 2). Re-challenge should be done every 6 months to evaluate tolerance. If symptoms still appear after re-challenge, infants should be back on free cow's milk protein diet for another 6 months [11].

Soy is recommended for infants above 6 months old who cannot tolerate extensively hydrolyzed formula in term of palatability or cannot get this formula due to cost or availability issues. Parents should be informed that some of CMA patients are also allergy to soy, therefore careful follow up should be done [11].

Soy formula consider to be safe for CMA patients in Indonesia, as Muktiarti et al. [18] found that only 17.5% patient with CMA sensitized to soy and Santi et al. [19] also found none of CMA patients were sensitized to soy. In addition, a lot of Indonesian traditional foods use soy as its ingredients.

Most of food allergy can be grow out in certain time. Routine assessment for tolerance is needed to avoid unnecessary extended avoidance of food allergen. We should observe for multiple food allergies and other allergic diseases in the future especially respiratory tract allergic disease [1].

Preventive measures are needed to prevent allergic diseases especially in children with atopic family. Studies on breastfeeding for preventing allergy showed conflicting results [3]. Indonesia national survey found that only 25.2% infant who had exclusive breastfeeding for 4 months, and 15.3% infants who had exclusive breastfeeding for 6 months [20]. Munasir et al. [21] found that breastfeeding has no impact on occurrence of atopic dermatitis. Nevertheless, we still encourage breastfeeding as allergy preventive measure. Partially hydrolyzed can be used for infants from atopic family who cannot get breastfeeding [11].