Development of childhood allergy in infants fed breast, soy, or cow milk

Atopic dermatitis: is it an allergic disease?

For many years controversy has surrounded the relation between allergy and atopic dermatitis. We critically review the evidence for the contribution of allergy, or IgE-mediated hypersensitivity reactions, to the pathogenesis of this disease. We conclude that, at present, there is scant evidence that allergy is central to the development of atopic dermatitis, although it may be an aggravating factor in a few patients. Hence there is little rationale for the routine use of allergy testing or dietary and environmental manipulation in the management of this disease.

Prevalence of atopic dermatitis in Leicester: a study of methodology and examination of possible ethnic variation

A study was undertaken to investigate and compare various methods of estimating the prevalence of atopic dermatitis (AD), and to investigate a possible ethnic difference in our local community. Preschool children attending routine child health surveillance clinics and Social Services day nurseries were examined by a trained observer, and their parents were interviewed. In addition, general practice records from a health centre were scrutinized. Three hundred and twenty-two children aged 1-4 years were examined, and the point prevalence of AD was 14% [95% confidence interval (CI) 10-18]. There was no apparent ethnic difference in prevalence. Twenty-seven per cent (95% CI 22-32) of parents reported that their children had suffered from 'eczema' at some time. General practitioners' records contained a diagnosis of 'eczema' in 32% (95% CI 28-36) of 446 children aged 1-4 years. It is clear that methodology must be carefully standardized if comparisons are to be made between different studies. Accurate estimations of the prevalence of AD can probably only be obtained by examination of a population sample by a trained observer. However, the estimates obtained in this study are high, and would tend to support existing evidence that the prevalence of AD is rising.

Factors influencing serum immunoglobulin E levels in Greek children

Serum levels of immunoglobulin E (IgE) were determined by enzyme immunoassay in 414 Greek infants and children of both sexes, 1 month to 14 years old. The children were admitted to the "Aghia Sophia" Teaching Hospital for Children (Athens, Greece) for surgical corrections of minor anatomic abnormalities, but they were otherwise healthy. Statistical analysis was performed through multiple regression after logarithmic transformation of the immunoglobulin values. IgE levels increased significantly by about 80% per year up to the age of 5 years, without noticeable impact of age on these levels thereafter. History of allergic disease showed a significant positive association with serum levels of IgE in both younger (less than 5 years) and older children. History of frequent infections was positively associated with IgE levels, although the relation was statistically significant only in the older age group, IgE levels in Greek children appear to be higher than the corresponding levels of children living in northern Europe, but much lower than those of children in Southeast Asia, a fact that may reflect different exposure level during childhood to infections known to influence IgE levels.

Food allergy in infancy

This article discusses the current understanding of the mechanisms of food hypersensitivity and presents a practical approach to the condition. Skin testing is a useful technique if properly applied and interpreted; however, double-blind placebo-controlled food challenge is the standard for accurate diagnosis against which all other tests should be compared. Treatment still consists of avoidance of the offending food allergens; however, most children lose their reactivity, and thus regular challenges are important.

Cow's milk protein intolerance in infants under 1 year of age: a prospective epidemiological study

Incidence and clinical manifestation of cow's milk protein intolerance (CMPI) were studied in 1158 unselected newborn infants followed prospectively from birth to 1 year of age. No food changes were required in 914 infants who were used as healthy controls. When CMPI was suspected (211 infants), diagnostic dietary interventions according to a standard protocol were performed. After exclusion of lactose intolerance, two positive cow's milk elimination/challenge tests were considered diagnostic of CMPI. Two hundred and eleven symptomatic infants were examined for possible CMPI. A large group of 80 infants improved on a lactose reduced formula. In 87/211 infants CMPI was excluded (sick controls). Finally CMPI was proven in 26 infants. The calculated incidence rate for CMPI was 2.8%. The principal symptoms in infants with CMPI were gastrointestinal, dermatological and respiratory in 50%, 31% and 19% respectively. A positive family history for atopy (first or second degree relatives) was more frequent in either CMPI infants (65%), or sick controls (63%) when compared to either healthy controls (35%) or infants improving on a low lactose formula (51%). Differences between patients with CMPI and sick controls were only found for the presence of atopy in at least 2 first degree relatives [(5/26 in CMPI infants and 4/87 in sick controls (P < 0.05)] and for multiorgan involvement [10/26 infants with CMPI as opposed to 12/87 in the sick control group (P < 0.02)]. These statistical differences are too weak to be of clinical value.

Cow milk allergy in infancy and hypoallergenic formulas

Substitute feedings have been used to treat infants with cow milk protein allergy for most of this century. For the past 50 years, several infant formulas based on animal proteins, both intact and chemically modified, or on vegetable protein have been labeled "hypoallergenic." Because of the risk of anaphylaxis and other serious adverse reactions, formulas that are claimed to be hypoallergenic should be subjected to rigorous preclinical and clinical testing. At a minimum, such formulas should not provoke any allergic signs or symptoms in 90% of infants with documented cow milk protein allergy when tested in double-blind, placebo-controlled trials. A standardized definition of "hypoallergenic" will allow clinicians and parents to understand the true risks to a cow milk-allergic infant fed such hypoallergenic formulas.

Interleukin 2 therapy in severe atopic dermatitis

Interleukin 2 (IL-2) at a dose of 10,000 to 20,000 U/kg/q 8 hr was given for 9-12 days to six patients with cases of severe atopic dermatitis (AD) which were refractory to conventional therapy. After IL-2 therapy, the clinical symptoms and signs of eczema including pruritus, scratching, papulovesicles, and lichenification were much improved, but all of them recurred 2-6 weeks after stopping treatment. Adverse reactions were similar to those reported previously, but all of them subsided after discontinuation of therapy. Laboratory findings showed decreased T-cell subsets, especially CD4+ cells, and increased IL-2R+ (CD25) cells, but there was no significant change in serum IL-2, serum IgE, or in vitro IgE production. Immunopathological studies of the skin biopsies showed decreased mononuclear-cell infiltration, depletion of CD4+ cells, and enhanced expression of CD25 and HLA-DR antigens. As lymphokine-activated killer (LAK)-cell activity against cultured fibroblasts was similar in patients with AD and in normals and CD1+ Langerhans cells were not decreased after IL-2 therapy, we speculate that the depletion of helper/inducer CD4+ cells and hence abrogation of the exaggerated antigen processing and cellular activation in diseased skin are the explanation for the transient efficacy of IL-2 in the treatment of atopic dermatitis.

Cows' milk sensitive enteropathy in cystic fibrosis

Proximal small intestinal mucosal biopsies were carried out in children with cystic fibrosis who had diarrhoea and failed to thrive in spite of adequate treatment, including pancreatic supplements. Histological examination of eight of the 17 biopsies taken over a period of 12 years showed evidence of enteropathy, and accounted for one in 13 (8%) children with cystic fibrosis under 3 years of age attending our clinic. Seven responded to a cows' milk free diet; the diarrhoea stopped and weight gain increased. One of these responded only when gluten was also excluded from his diet. The eighth child remained on a normal diet and his symptoms did not improve. The enteropathy had resolved in all five patients who had further biopsies taken while receiving treatment, and from 15 months to 3 years of age all the children tolerated a normal diet and continued to thrive. Cows' milk sensitive enteropathy is an important cause of failure to thrive in children with cystic fibrosis. Small intestinal biopsy is an important investigation in younger children who fail to thrive and have diarrhoea despite adequate treatment.

The natural history of IgE sensitisation and atopic disease in early childhood

We have prospectively followed 57 children of atopic parents up to 5 years of age, documenting clinical atopic disease and allergen skin test reactions. The cumulative prevalences of the clinical features of atopic disease over the 5 years were: atopic dermatitis (58%), wheeze (49%), recurrent wheeze (33%), rhinitis (68%) and immediate food reactions (18%). Atopic dermatitis and immediate food reactions predominated in infancy (birth to 20 months) while wheezing was more prominent in later childhood (20 months to 5 years). Rhinitis was common in both infancy and childhood. IgE sensitisation to ingested allergens was prominent in early infancy and was usually transient. Inhaled allergen sensitisation occurred later in infancy and was generally permanent with wheal sizes tending to increase with age. There was a significant association between IgE sensitisation to ingested but not inhaled allergens and all atopic manifestations in infancy, with the exception of rhinitis. In contrast IgE sensitisation to inhaled allergens was associated with rhinitis and wheeze in later childhood. We found two clinical groups. One group, with only ingested allergen sensitisation had a high incidence of atopic dermatitis but low incidence of respiratory symptoms at 5 years of age. The other group, who developed evidence of IgE sensitisation to inhaled allergens, had a high incidence of rhinitis and wheeze but low incidence of atopic dermatitis at 5 years of age.

Role of diet in treating atopic eczema: elimination diets can be beneficial

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Cord serum IgE in relation to family history and as predictor of atopic disease in early infancy

Cord serum IgE was assayed by particle counting immunoassay (PACIA) in an unselected series of European newborns (n = 190; geom mean = 0.37 IU/ml) and a cut-off limit established (greater than or equal to 1.20 IU/ml) for prediction of atopy. At control follow-up by questionnaire 18 months after birth, 38 infants (20.0%) had developed definite (9.5%) or probable (10.5%) atopy with a significant predominance of boys (P less than 0.03). Infants with a positive immediate family history (IFH) had a higher risk of developing atopy (P less than 0.0025) and also had a higher incidence of elevated cord IgE (P less than 0.02) than infants with a negative IFH. Maternal atopy influenced cord IgE levels significantly (P less than 0.00005), whereas paternal atopy did not (P = 0.23). No fetal IgE antibodies against five common allergens could be demonstrated in 36 cord sera tested. Breast-feeding for 3 months was not sufficient to prevent atopic symptoms. The predictive value of cord IgE was high since 26 of 36 newborns (positive predictive value = 72.2%) with elevated cord IgE had developed atopic symptoms before follow-up. Of the 38 infants who developed atopic symptoms, 26 had elevated cord IgE (sensitivity = 68.4%) compared to only 10 (6.6%) of the 152 atopy-free infants (P less than 0.00005). The data indicate that elevated cord IgE as determined by PACIA is a good predictor of early-onset atopy, better than family history (P less than 0.008), and that primarily maternal atopy seems to affect fetal IgE synthesis.

Does breast feeding help protect against atopic disease? Biology, methodology, and a golden jubilee of controversy

To help shed some light on the 50-year-old controversy concerning the possible protective effect of breast feeding on subsequent atopic disease, I developed 12 standards pertaining to both biologic and methodologic aspects of exposure (infant feeding), outcome (atopic conditions), and statistical analysis for studies of atopic eczema, asthma, allergic rhinitis, cow milk allergy, and other food allergy. Among the published studies on atopic eczema, the nine claiming a protective benefit of breast feeding performed less well than the 12 not making such a claim on "methodologic" standards relating to strict diagnostic criteria and blind ascertainment of outcome. The positive studies were somewhat stronger, however, on the "biologic" standards bearing on sufficient duration and exclusivity of breast feeding and on separate analysis of children at high risk. For the other atopic conditions, there were no important differences between positive and negative studies. In few negative or positive studies was there adequate control for confounding variables or examination of potential benefits relating to the severity or age at onset of atopic disease. To avoid another 50 years of unresolved controversy, future studies should improve both the biologic and methodologic aspects of their design and analysis.

A comparison of the antigenicity of soya-bean-based infant formulas

1. The antigenicity of four soya-bean-based infant formulas (Prosobee powder, Prosobee liquid concentrate (Mead Johnson, Uxbridge, Middx), Wysoy (Wyeth, Maidenhead, Berks) and Formula S (Cow and Gate, Trowbridge, Wilts] was measured by enzyme-linked immunosorbent assays (ELISAs) specific for glycinin and beta-conglycinin. Results were compared with in vivo assessments of antigenicity using guinea-pigs, rabbits and calves. 2. The levels of antigenic glycinin and beta-conglycinin in Wysoy and Formula S were below the limits of detection of the ELISA. Both these proteins were detected in Prosobee powder and Prosobee liquid concentrate with the highest levels, especially for glycinin, being present in Prosobee powder. 3. Wysoy was sufficiently antigenic to evoke a soya-bean-specific serum antibody response in rabbits injected with this formula emulsified in complete Freunds adjuvant. A significantly greater response was obtained when rabbits were similarly injected with Prosobee powder. 4. The formulas varied in their ability to sensitize guinea-pigs for both anaphylaxis and antibody production when given orally, although the differences were not statistically significant. Prosobee powder appeared to be the most antigenic and Formula S the least, with Prosobee liquid concentrate and Wysoy being intermediate. 5. Similar variations in antigenicity were observed when Prosobee powder, Wysoy and Formula S were fed to soya-bean-sensitive calves. These formulas were all capable of provoking intestinal disturbances (seen as increased ileal flow-rate, decreased small intestinal transit time and decreased nitrogen absorption) but the most severe reactions were seen when Prosobee powder was fed and the least with Formula S. 6. Thus the four soya-bean-based infant formulas showed considerable differences in antigenicity. In vivo studies using guinea-pigs, rabbits and calves were in good agreement and broadly correlated with the immunochemical assessment of antigenicity. However, the in vitro and in vivo results did not correspond exactly and levels of glycinin and beta-conglycinin below the limit of detection by ELISA could evoke an immune response in the different animal species. We believe that these variations in antigenicity of different commercial products prepared from isolated soya-bean protein may be important when interpreting the results from studies of the development of allergy in infants given soya-bean-based formulas.

Acute bronchiolitis: predisposing factors and characterization of infants at risk

Fifty-one infants hospitalized because of acute bronchiolitis and 24 control children were prospectively followed until 2 years of age. Respiratory syncytial virus was detected initially in 31 index children, parainfluenza virus in two, and rhinovirus in one. More index children were born during the months April through September, and six index children had neonatal respiratory complications. The index children were breast-fed for shorter periods, lived in more crowded homes, and had more siblings. No significant differences were found for atopic background and atopic illness at 2 years of age. The index children had more respiratory infections and episodes of bronchopulmonary obstruction during the follow-up period (60% with three or more episodes). To characterize the hospitalized children, a discriminant analysis was performed. A discriminant function classified 47 of 51 index children as belonging to the index group and 21 of 24 control children to the control group.

Prolonged exclusive breast feeding and heredity as determinants in infantile atopy

We followed 183 infants for two years, 31 of whom were breast fed less than three and a half months (median 70 days; short breast feeding group) and a further 31 of whom were exclusively breast fed for more than nine months (long breast feeding group). We assessed heredity for atopy, number of infections, and duration of breast feeding as determinants of atopy. During the first year of life 14 infants has signs of atopy. During the second year parents reported signs of atopy in a further 31. Heredity was the only significant predictor of atopy. Atopy was seen in 33% of infants with a positive heredity and in 16% without family history for atopy. The duration of breast feeding affected the incidence of atopy only among the infants without family history for atopy: fewer in the short breast feeding group (1/18) had atopy than in the long breast feeding group (5/13). Duration of breast feeding did not associate with incidence of respiratory infections. Diarrhoea was more common in the short breast feeding group than in the long breast feeding group during the first year of life. We conclude that prolonging exclusive breast feeding from the median of 70 days to nine months did not contribute to the prevention of infantile atopy and respiratory tract infections.

[Physiologic nutritional evaluation of complete infant nutrition based on a soybean formula]

The purpose of this review is to evaluate the nutritional quality of soybean-based infant diets on the basis of results published in the scientific literature. Special consideration has been given to the use of soybean protein formulas for infants with reduced intestinal digestion and absorption capacity as well as in cases of cow's milk intolerance and allergic diseases.

Presence of IgE suppressor factors in human colostrum

In spite of intensive investigations, the ability of breast feeding to delay and to attenuate atopic diseases in children remains debatable. This study documents a mechanism whereby breast feeding might interfere with the synthesis of IgE by breast-fed infants. Indeed, we show that colostrum contains IgE-binding factors (IgE-BF) capable of suppressing the in vitro synthesis of human IgE. Colostrum obtained from 15 donors was successively depleted of lipids and casein, filtered through Amicon XM50 membrane (mol. mass cut-off 50 kDa) and lyophilized. IgE-BF was demonstrated in such preparations by two different approaches, i.e. a classical rosette inhibition assay and Western blot analysis. In the first instance, lyophilized preparations of colostrum inhibited the binding of IgE-coated bovine erythrocytes to IgE recovered on the surface of RPMI 8866 lymphoblastoid cells. The rosette-inhibiting activity could be absorbed on IgE- but not on IgG-Sepharose 4B and it could be recovered in the eluate of IgE-Sepharose 4B. The molecular mass of IgE-BF was comprised between 10 to 20 kDa as estimated by gel filtration through a calibrated Sephadex G-75 column. After fractionation on 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transfer to nitrocellulose membrane, colostrum displayed one band of 14 kDa and reacted with radiolabeled IgE but not with IgG nor IgM. This 14-kDa band could be removed by absorbing colostrum with IgE- but not with IgG-Sepharose 4B. Most importantly, the colostrum IgE-BF suppressed the spontaneous in vitro synthesis of IgE by B lymphocytes derived from allergic donors without altering the production of IgM.

Does natural sensitisation in eczema occur through the skin?

The specificities of serum IgE for the faecal and body antigens of the house-dust mite, Dermatophagoides pteronyssinus, were compared in 69 children with various combinations of asthma, eczema, and/or rhinitis. The concentration of IgE antibodies to the mite body was higher in those with eczema than in those with asthma, but the concentrations of IgE antibodies to the faecal allergen were not significantly different. The ratio of the serum concentration of anti-mite-body IgE to anti-faecal IgE was significantly greater in the children with eczema than in the children with asthma. The results in 4 subjects with rhinitis (2 with and 2 without eczema) support the view that IgE antibodies to the mite body are characteristic of eczema. Sensitisation to mite body and mite faecal particles may occur by different processes; the allergens of mite bodies may penetrate the skin, whereas faecal allergen may enter the body by other route(s).

The role of "allergy" in atopic dermatitis

Atopic dermatitis is a disorder that affects up to 4.3% of the pediatric population. Its etiology is unknown, but is probably multifactorial. Evidence has been presented to implicate a role for "allergy" in the pathogenesis of AD. Disregarding the myriad of clinical reports, there is sufficient data in the literature to suggest an etiologic role for inhalants (pollen, mold, and dust mite) and foods in some patients with AD. Definitive studies have demonstrated that both inhalant and food antigens can be absorbed rapidly and transported to the skin, where sensitized mast cells can be activated. Controlled challenges have demonstrated skin reactions following exposure to inhalant and food antigens in sensitive subjects. Activiation of mast cells and/or basophils has been shown following oral food challenges in sensitized children with AD. Although sufficient evidence is now available to implicate "allergy" as an etiologic factor in atopic dermatitis, the link between mast cell activation and the development of eczematous skin changes remains to be clearly defined.

Significance of food hypersensitivity in children with atopic dermatitis

Abstract: Some of us are old enough to recall reading Lewis Webb Hill's monograph entitled The Treatment of Eczema in Infants and Children (St. Louis: CV Mosby, 1956). Its epilogue is a quotation from Claude Bernard's Introduction to Experimental Medicine, words that seem most fitting as a prologue to this symposium:

Food hypersensitivity and atopic dermatitis: evaluation of 113 patients

One hundred thirteen patients with severe atopic dermatitis were evaluated for food hypersensitivity with double-blind placebo-controlled oral food challenges. Sixty-three (56%) children experienced 101 positive food challenges; skin symptoms developed in 85 (84%) challenges, gastrointestinal symptoms in 53 (52%), and respiratory symptoms in 32 (32%). Egg, peanut, and milk accounted for 72% of the hypersensitivity reactions induced. History and laboratory data were of marginal value in predicting which patients were likely to have food allergy. When patients were given appropriate restrictive diets based on oral food challenge results, approximately 40% of the 40 patients re-evaluated lost their hypersensitivity after 1 or 2 years, and most showed significant improvement in their clinical course compared with patients in whom no food allergy was documented. These studies demonstrate that food hypersensitivity plays a pathogenic role in some children with atopic dermatitis and that appropriate diagnosis and exclusionary diets can lead to significant improvement in their skin symptoms.

Predictive value of cord blood IgE in the development of atopic disease and role of breast-feeding in its prevention

The predictive value of cord blood IgE in the development of atopic disease was evaluated in a prospective study of two groups of infants. Total serum IgE level was greater than or equal to 0.7 U/ml in 44.3% of the infants with positive family history of atopy and in 16.0% among those with negative family history. The level of cord blood IgE correlated significantly with the subsequent development of atopic disease in both groups. Cord blood IgE higher than 0.7 U/ml was associated with a high risk of development of atopic eczema and wheezing, 52.8% and 58.8% respectively in the groups with or without family history of atopy; compared with 13.4% and 1.1% in the groups with IgE levels less than 0.7 U/ml. Among newborns fed exclusively on breast milk for a minimum of 3 months, the incidence of eczema and wheezing was significantly lower (12%) compared with findings in the formula-fed group (32%).

Problems of early infancy, formula changes, and mothers' beliefs about their infants

Problems of early infancy are sometimes managed by changing an infant's formula from a cow milk formula to a soy protein or casein hydrolysate formula ("special formulas"). This study was designed to determine the frequency of formula changes, mothers' reports of problems that lead to such a change, and mothers' beliefs about the causes of these problems. Mothers of 189 breast-feeding (BF) and 184 formula-feeding (FF) infants were enrolled postpartum. Follow-up data were obtained by telephone interviews at 4 months. After starting a cow milk formula, 11% of the BF and 25% of the FF infants were given special formulas. Mothers frequently reported problems related to feeding, bowel movements, and crying behavior; 32% of infants with such problems were given special formulas. Excessive crying and colic were the most common problems leading to a formula change. When a formula was changed, mothers more frequently believed that the cause of the problem was intrinsic to the child (P less than 0.001) and that their infant had had a "disease or illness" (P less than 0.001). When formula changes occurred, 26% of mothers believed that their infants were allergic to cow milk. These beliefs may affect a mother's perceptions of her child's vulnerability.

Food allergy and intolerance

This article focuses on intolerance to food proteins, discussing the definition and history of food intolerance, the basics of gastrointestinal mucosal immunity, specific food antigens, pathogenesis, clinical manifestations, as well as diagnosis, therapy, and prevention.

Passage of cows' milk protein in breast milk

An enzyme-linked immunosorbent assay has been used to search for lactoglobulin and bovine casein in breast milk. Initial results suggest this may be a simple and useful method for such studies. Detection and prevention of antigen passage could influence the prevalence of atopic disease.

Increased plasma histamine concentrations after food challenges in children with atopic dermatitis

Thirty-three patients with atopic dermatitis underwent double-blind placebo-controlled food challenges for evaluation of the role of histamine in hypersensitivity to food. After suspect foods were eliminated for 10 days, oral challenges were performed with up to 8 g of dehydrated food. A total of 35 positive challenges elicited symptoms that were cutaneous (31), gastrointestinal (17), nasal (8), and respiratory (6) within 10 to 90 minutes. Forty-one food challenges were negative, and all 60 placebo challenges were negative. Only the group of patients with positive food challenges had a significant mean (+/- S.E.M.) rise in the plasma histamine concentration, from 296 +/- 80 pg per milliliter before challenge to 1055 +/- 356 after challenge (P less than 0.001). Rises in plasma histamine that were seen after these positive oral food challenges implicate mast-cell or basophil mediators in the pathogenesis of food allergy, including cutaneous changes in patients with atopic dermatitis.

Breastfeeding and eczema

198 infants were followed up from birth until 4 1/2-5 years to observe the development of eczema and asthma and its relation to infant feeding. Findings here refer only to eczema. Comparison between those initially breastfed, regardless of duration, and those fed on cows milk preparations showed little difference in the incidence of eczema, but there was a higher incidence of eczema in those with an immediate family history of atopy than in those with no such history. Comparison of infants breastfed for less than and more than 12 weeks showed: the incidence of eczema fell in infants with an immediate family history of atopy when exclusive breastfeeding was continued beyond 12 weeks, whereas the incidence of eczema rose in all breastfed infants, regardless of their atopic family history, when breastfeeding, combined with other foods, was continued beyond 12 weeks.

A prospective study of the clinical manifestations of atopic disease in infancy

We prospectively followed a group of infants with a family history of atopy, from birth for up to 20 months of age. All infants were seen every 4 months and a history, physical examination and skin tests obtained. Atopic dermatitis and rhinitis occurred in about half the infants at some time during the study, while wheezing occurred in about a quarter. Both atopic dermatitis and rhinitis were more common in the first 12 months whereas wheezing occurred later and increased in prevalence with age. Defining atopy by the presence of atopic dermatitis or positive skin tests, only immediate food reactions were significantly associated with atopic infants. In contrast, rhinitis, a single episode of wheezing, colic, vomiting and delayed food reactions were not associated with atopy and thus are unlikely to be due to IgE-related mechanisms during infancy.