Crete: does farming explain urban and rural differences in atopy?

BACKGROUND: Urban-rural differences in the prevalence of atopy and associated allergic diseases have been reported in several non-European countries. Within Europe, where such variations are less striking, a farm childhood has been postulated to be protective. OBJECTIVE: We aimed to compare the prevalence of atopy in urban and rural children living in Crete and to examine the role of early exposure to a farming environment in explaining any measured differences. METHODS: A cross-sectional survey of children attending secondary schools in Iraklion, the capital city, and five villages 100 km to the south. Atopy was determined by the responses to skin prick tests with seven common aeroallergens. RESULTS: Nine-hundred and ninety-seven children participated in the survey. 19.6% of those living in Iraklion, but only 9.6% of those from the villages, had a positive response to one or more skin prick tests. Among urban children there were significant gradients in the prevalence of atopy across several categories of animal contact and consumption of farm (unpasteurized) milk products--before the age of 5 years. These differences, however, were not apparent among the rural children.     

Risk factors for atopy among school children in a rural area of Latin America

BACKGROUND: Infection with common childhood infectious diseases including geohelminth infections may provide protection against the development of atopy and allergic disease. Few studies have investigated risk factors for atopy among children living in rural areas of Latin America. OBJECTIVE: To identify risk factors associated with atopy among school-age children in a rural area of Latin America. METHODS: Analytic cross-sectional study of school-age children conducted in seven rural schools in Pichincha Province in Ecuador. Detailed risk factor information was obtained by questionnaire, stool samples were collected for identification of geohelminth parasites, and Mantoux testing was performed to determine tuberculin sensitization. RESULTS: A total of 1002 children from seven rural schools were recruited. The prevalence of geohelminth infections was high (70.1% were infected with at least one geohelminth parasite) and the prevalence of allergic sensitization was high (20.0% had evidence of aeroallergen sensitization). Factors associated with significant protection against atopy in multivariate analyses were the presence of overcrowding in the child's home, low socio-economic level, and infection with geohelminth parasites, and the protective effects of the three factors were statistically independent. CONCLUSION: Low socio-economic level, overcrowding and geohelminth infection, are independently protective against atopy among school-age children living in a rural area of Latin America.     

Absence of association between delayed type hypersensitivity to tuberculin and atopy in children in The Gambia

BACKGROUND: An inverse association between delayed type hypersensitivity to tuberculin and atopy has been observed in children, suggesting that exposure to mycobacteria may influence the immune response to allergens. OBJECTIVE: To investigate the relationship between tuberculin responses and atopy in children living in three different environments in The Gambia. METHODS: In this cross-sectional study a total of 507 school-aged children were recruited from rural, urban poor or urban affluent communities. They were assessed for skin responses to five common allergens and tuberculin, presence of bacille Calmette-Guérin (BCG) scar, presence of intestinal parasites, and total serum IgE. Atopy was defined as the presence of a skin prick test response > or = 3 x 3 mm to at least one allergen. RESULTS: The overall prevalence of atopy was 33% but there was a significant variation among the three study groups. The prevalence of atopy was 22% in urban poor, 36% in urban affluent, and 43% in rural children. Controlling for potential confounding factors, children in the rural community had a significantly higher odds ratio, 3.3 (95% confidence interval 1.8-6.0) of being atopic than children from the urban poor community. No association between atopy and tuberculin response or BCG scar was observed in any of the three groups. Serum IgE levels were higher among children of the urban poor group but were not associated with tuberculin response or BCG scar in any of the groups. CONCLUSION: Environmental factors have an important influence on the development of atopy in children in The Gambia but delayed type hypersensitivity to tuberculin is not a protective factor.     

Gaseous air pollution and atopy

BACKGROUND: Photochemical air pollutants are commonly thought to be implicated in the gradual increase in the prevalence of atopy. However, no epidemiological data are available. METHODS: To clarify this issue, we performed a cross-sectional epidemiological survey in 2604 primary school children, 10 and 11 years old, living in seven communities among which some have the highest photochemical exposure in France. The mean levels of the main gaseous air pollutants (SO2, NO2 and O3) were measured during a 2-month period in 1993. The protocol included a standardized questionnaire, skin prick tests to common aeroallergens and in the atopic children, collection of a sample of mattress dust to measure group 1 mite allergens. Atopy was only defined on the basis of the skin prick tests. RESULTS: Percentage of positive skin tests and the number of positive skin tests were similar in the different communities looked at. The distribution of dust samples with a group 1 allergen level greater than 2 microg/g dust, was also similar. Logistic regression analysis including potential confounding factors, as well as the mean level of air pollutants, did not demonstrate any association between atopy and mean SO2, NO2 and O3 levels. CONCLUSION: The increase in photochemical air pollutants is unlikely to be a major determinant for the recent increase in the prevalence of atopy.     

Ethnicity, childhood environment and atopic disorder

BACKGROUND: The International Study of Asthma and Allergies in Childhood (ISAAC) has demonstrated large differences in the prevalence of atopic disorders in children between different regions in the world. Populations with a higher standard of living and a more westernized lifestyle tend to have higher rates of atopy and asthma. Many hypotheses regarding environmental causes of atopic disorder focus on the early childhood environment. OBJECTIVE: To study the influence of ethnicity and country of birth for the prevalence of atopic disorders. METHODS: The prevalence of atopic disorders in Swedish residents born in Turkey and Chile, who settled in Sweden as adults in the 1980s, was compared with their own Swedish-born children and a sample of Swedish-born parents and their children in interview data from the Survey of Living Conditions in 1996. The study group included 1734 adults 27-60 years of age and their 2964 children aged 3-15. RESULTS: The Chilean-born parents and their children had the highest risk for allergic asthma; adjusted odds ratios (ORs) 2.2 (1.2-4.0) and 2.7 (1.6-4.5), respectively, and allergic rhino-conjunctivitis; OR 1.6 (1.1-3) and 1.6 (1.1-2.5) in both groups, when compared with the Swedish-born parents and their children. The Turkish-born parents and their children had the lowest risk for allergic rhino-conjunctivitis; both groups had OR 0.6 (0. 4-0.9) and the children in this group also had the lowest risk for eczema; OR; 0.4 (0.3-0.7). The risk for all atopic disorders was lower in the Turkish group compared with the Chileans. CONCLUSION: This study demonstrates that ethnicity is an important determinant of atopic disorder independent of the external childhood environment. The value of international comparisons of environment and risk for atopic disorders can be questioned until more is known about factors related to ethnicity, such as genetic susceptibility and diet, for the development of atopy.     

Which factors explain the lower prevalence of atopy amongst farmers' children?

BACKGROUND: The inverse association between farming and atopy in children has been attributed to microbial exposure, especially through livestock. Very little is known about other potential explanatory factors. OBJECTIVE: To explore potential differences in lifestyle and environmental factors between farmer and non-farmer families, and whether these factors could explain the association between farming and childhood atopy. METHODS: A cross-sectional study, including 366 farmers' and 344 non-farmers' children in eastern Finland. Information regarding exposure and background characteristics was gathered by a written questionnaire. Atopy was defined as having one or more positive skin prick test reactions (> 3 mm) against the six common aeroallergens. RESULTS: Regardless of the current farming type, atopy was less frequent among the farmers' children than the non-farmers' children (aOR 0.56, 95% CI 0.40-0.78). Remarkable differences were seen in many lifestyle factors (including diet) between the farmer and non-farmer families, but only a few of the explored factors were associated with atopy. The frequency of current livestock contacts seemed to have an inverse, dose-dependent association with atopy (aOR 0.46, 95% CI 0.22-0.97 for daily vs. no contact). Having lived on a dairy farm in infancy (aOR 0.51, 95% CI 0.28-0.93), or having had cats or dogs in infancy (aOR 0.60, 95% CI 0.42-0.85), decreased the risk of atopy at school age. The inverse association between farming and atopy was not explained by the sociodemographic factors, or by differences in conventional risk factors of atopy. Animal contacts explained partially, but not completely, the association. CONCLUSION: Higher frequency of animal contacts is one factor, but probably not the only one, explaining the inverse association of farming and atopy in children. The importance of early life exposures may have recently been over-emphasized, and current exposures discounted, when studying the risk factors of childhood atopy.     

Childhood atopy and allergic disease and skin test responses to environmental mycobacteria in rural Crete: a cross-sectional survey

BACKGROUND: Through its powerful immunoregulatory effects, infection with atypical mycobacteria may exert a protective effect on the development of childhood allergic disease. OBJECTIVE: To examine the relationship between childhood atopy or allergic disease and previous infection with four species of atypical mycobacteria. METHODS: Eight hundred and six children aged 8-18 years and living in rural Crete--most of whom had had previous BCG immunization--underwent skin prick testing with 10 aeroallergens; their parents completed a standardized questionnaire relating to allergic disease. No less than 8 weeks later each child underwent intradermal skin tests with 0.1 mL solutions of four selected mycobacterial reagents (Aviumin C, Gordonin, Chelonin and Ranin I). RESULTS: Twenty-three percent of children were atopic on skin prick testing; far fewer had symptoms of asthma (5%) or hayfever in conjunction with a positive prick test to pollens (2%). Eighty percent of children had positive skin responses to one or more mycobacterial species. Among all children--and those with a BCG scar--there was no association between atopy or allergic symptoms and mycobacterial skin responses; among the few children without a BCG scar however those with positive mycobacterial responses were less likely to be atopic or to report allergic symptoms; these differences were not statistically significant. CONCLUSIONS: Our findings, in a population of BCG-immunized children, do not lend support to the suggestion that infection with atypical mycobacteria is protective against childhood allergic disease.     

Relationships of allergic sensitization, total immunoglobulin E and blood eosinophils to asthma severity in children of the EGEA Study

BACKGROUND: Although allergy is highly associated with childhood asthma, it is not well known if there is a relationship between the intensity of allergic sensitization and asthma severity. OBJECTIVE: The objectives of the study were to examine the relationships between several markers of allergy and asthma severity in asthmatic children included in the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyper-responsiveness and atopy (EGEA). METHODS: The population comprised 216 asthmatic children below 16 years of age. Total IgE and blood eosinophil counts were measured and skin prick tests to 11 aeroallergens were performed. The intensity of the allergic sensitization was assessed by the number of positive skin prick tests and by skin weal sizes. Asthma severity was measured with four criteria: a clinical severity score, history of hospitalization for asthma, FEV1% predicted and inhaled steroid use in the last 12 months. RESULTS: Most of the children were sensitized to at least one aeroallergen (88.2%). Atopy was not related to the severity of asthma, except for a tendency for a more severe clinical score in non-atopic children. The type and intensity of the allergic sensitization were not associated with any criteria of asthma severity. Total IgE was significantly increased in children treated with inhaled corticosteroids and in children ever hospitalized for asthma (P-values 0.009 and 0.04, respectively). Eosinophil counts were not related to asthma severity. CONCLUSION: Our results suggest that severe childhood asthma may be related to a high level of total IgE but not to blood eosinophil counts. The lack of positive relationships between both atopy and the intensity of allergic sensitization with asthma severity supports the hypothesis of different risk factors being associated with asthma and with the severity of asthma.     

A dual long-term effect of breastfeeding on atopy in relation to heredity in children at 4 years of age

BACKGROUND: The long-term effect of early feeding on atopic sensitization is still unsolved. The aim of this study was to evaluate the long-term effect of breastfeeding on atopy in groups of 4-year-old children stratified by atopic heredity. METHODS: We collected four groups of 4-year-old children from a birth cohort: two groups with differing backgrounds of atopic heredity, all exclusively breast-fed for at least 3 months; and two groups with differing atopic heredity, but all fed with cow's milk-based formula during their first weeks. The data were collected with a questionnaire, skin prick testing, and measurement of serum total and allergen-specific IgE levels. RESULTS: Breastfeeding significantly decreased the risk of allergic rhino-conjunctivitis [odds ratio (OR) 0.41, 95% confidence interval (CI) 0.18-0.95] and sensitization to furred pets, as measured by skin prick results, in children with atopic heredity, whereas in children without atopic heredity, breastfeeding was related to an increased risk of symptomatic atopy (OR 2.57, 95% CI 1.16-5.70), and high serum IgE values. A significant interaction was found between heredity and breastfeeding. CONCLUSIONS: The long-term effect of breastfeeding was dual: in children with atopic heredity, breastfeeding protected against atopy, whereas in children without atopic heredity, it increased the risk of atopy.     

Dog exposure in infancy decreases the subsequent risk of frequent wheeze but not of atopy

BACKGROUND: Influence of household pets in the development of childhood asthma or atopy has been controversial. OBJECTIVE: The purpose of this study was to investigate whether pet exposure in early life decreases the subsequent risk of frequent wheezing and/or allergic sensitization. METHODS: This was a prospective observational birth cohort study. The setting was a large health maintenance organization in Tucson, Ariz; the subjects were a population sample of 1246 newborns enrolled at birth and followed prospectively to age 13 years. The main outcome measures were as follows: time to first report of frequent wheezing (>3 episodes in the past year), skin prick test reactivity at 6 years and 11 years of age, and total serum IgE at 9 months, 6 years, and 11 years of age. RESULTS: Children living in households with > or =1 indoor dogs at birth were less likely to develop frequent wheeze than those not having indoor dogs (P =.004). This inverse association was confined to children without parental asthma (hazard ratio = 0.47; P <.001 [Cox regression]) and was not evident for children with parental asthma (hazard ratio = 0.96; P =.87). Adjustment by potential confounders did not change the results. Indoor cat exposure was not significantly associated with the risk of frequent wheezing. Neither cat exposure in early life nor dog exposure in early life was associated with skin prick test reactivity or total serum IgE at any age. CONCLUSION: Dog exposure in early life might prevent the development of asthma-like symptoms, at least in low-risk children with no family history of asthma. Nevertheless, early pet exposure does not seem to significantly influence the development of allergic sensitization.     

Prevention of asthma during the first 5 years of life: a randomized controlled trial

BACKGROUND: Early life exposures may be important in the development of asthma and allergic disease. OBJECTIVE: To test house dust mite (HDM) avoidance and dietary fatty acid modification, implemented throughout the first 5 years of life, as interventions to prevent asthma and allergic disease. METHODS: We recruited newborns with a family history of asthma antenatally and randomized them, separately, to HDM avoidance or control and to dietary modification or control. At age 5 years, they were assessed for asthma and eczema and had skin prick tests for atopy. RESULTS: Of 616 children randomized, 516 (84%) were evaluated at age 5 years. The HDM avoidance intervention resulted in a 61% reduction in HDM allergen concentrations (microg/g dust) in the child's bed but no difference in the prevalence of asthma, wheeze, or atopy (P > .1). The prevalence of eczema was higher in the active HDM avoidance group (26% vs 19%; P = .06). The ratio of omega-6 to omega-3 fatty acids in plasma was lower in the active diet group (5.8 vs 7.4; P < .0001). However, the prevalence of asthma, wheezing, eczema, or atopy did not differ between the diet groups (P > .1). CONCLUSION: Further research is required to establish whether other interventions can be recommended for the prevention of asthma and allergic disease. CLINICAL IMPLICATIONS: House dust mite avoidance measures and dietary fatty acid modification, as implemented in this trial during infancy and early childhood, did not prevent the onset of asthma, eczema, or atopy in high-risk children.     

Atopy in Danish children and adolescents: results from a longitudinal population study.

BACKGROUND AND OBJECTIVE: Atopy is an objectively measurable trait related to the presence of rhinitis and asthma, but our knowledge about its longitudinal predictors is limited. Data from a 6-year follow-up study of a population sample of children and adolescents (n = 408), aged 7 to 17 years at enrollment, were analyzed to investigate the prevalence and predictors of atopy. METHODS: Case history, including allergic diseases and smoking habits, was obtained by interview and questionnaire. Skin prick test reactivity to common allergens, total serum IgE, airway responsiveness, and pulmonary function were measured using standard techniques. RESULTS: The point prevalence of atopy increased from the first to the second survey, 26% and 44%, respectively; 23% of the participants had a positive skin prick test only at the second survey. Sensitization to house dust mite (HDM) (P < .001), grass (P < .001), dog (P < .001), cat (P < .001), and birch (P = .02) increased significantly in both males and females. No gender differences in the prevalence of positive reactions were found at the first survey, whereas atopy to grass (P = .01) and HDM (P = .02) were more prevalent in males than in females at the second survey. Confining the analysis to participants who were found to be non-atopic at the first survey showed that exposure to maternal smoking (OR 2, CI 1.3 to 3.1; P = .002), increased serum IgE (OR 1.7, CI 1.2 to 2.3; P = .001), new asthma (OR 1.6, CI 1.2 to 2.7; P = .03), and new rhinitis (OR 2.1, CI 1.2 to 3.6; P = .01), but not active smoking, were associated with an increased risk for the presence of a positive skin prick test at the second survey. CONCLUSIONS: This longitudinal population study showed an increase in the point prevalence of atopy in Danish children and adolescents; and, furthermore, that exposure to maternal smoking during childhood, increased serum IgE, and new symptoms of asthma or rhinitis were associated with an increased risk for developing sensitization to common aeroallergens in late adolescence.     

Inhibition of IgE production in vitro by intact and fragmented intravenous immunoglobulin

BACKGROUND: Antigen exposure in early life has long-lasting effects on atopic sensitization. Thus the predisposition to atopy of children born preterm can be assumed to differ from that of children born at term. OBJECTIVE: The aim of this study was to evaluate the association between premature birth and atopy. METHODS: At an outpatient clinic, we examined 2 groups of 10-year-old children, 72 who were born preterm (birth weight < 1500 g) and 65 who were born at term (birth weight > 2500 g). The atopy data were collected with a questionnaire, by performing skin prick testing, and by measuring the serum total IgE level, 3 allergen-specific IgE levels, the eosinophil cationic protein level, and the blood eosinophil level. The data on perinatal and neonatal events affecting the preterm children were collected from the hospital records. RESULTS: By the age of 10 years, the children born preterm had significantly less atopy than the children born at term: 15% versus 31% of children in the 2 groups were defined as having had obvious atopy (P = .03, odds ratio 0.41, 95% CI 0.18-0.93). The mean value of total IgE level was significantly higher in the term group, 74 kU/L versus 41 kU/L (P = .02). By skin prick testing, the children born at term had positive reactions 2 to 3 times more often; 37% versus 17% of children in the groups had at least 1 positive reaction (P = .007). CONCLUSION: Our data show that prematurity at birth is linked with a decreased long-term risk of atopic sensitization.     

Prevalence of allergy, patterns of allergic sensitization and allergy risk factors in rural and urban children

BACKGROUND: We aimed to compare the prevalence of allergic diseases and sensitization in children living in urban and rural areas and to identify potential risk/protection factors associated with allergy. METHODS: School children 12-16 years old, from urban community (n = 201) and rural area (n = 203) were recruited. The data obtained by questionnaire were referred to doctors' diagnosis, skin prick tests (SPTs), and serum specific and total IgE assessment. RESULTS: The prevalence of allergic diseases in urban children was significantly higher as compared with rural children [asthma 16.42%vs 1.97% (P < 0.001) allergic rhinitis 38.81%vs 10.84% (P < 0.001)]. Positive SPTs to at least one allergen was found in 63.7% of urban and 22.7% rural children (P < 0.001). Significantly higher percentage of allergic rural than urban children were monosensitized or sensitized to 2-4 allergens, but almost a fourfold higher percentage of allergic urban children was found to be sensitized to five or more allergens (P < 0.0001). The history of frequent upper respiratory factor (URT) infections, antibiotic therapy, tonsiltectomy/adenoidectomy were positively associated with development of atopy and sensitization. CONCLUSION: Our findings confirm that residence of rural area is associated with a significant lower prevalence of allergic sensitization and symptoms in school children. Several risk and protective factors related to environment and style of life could be identified in both environments.     

The protective role of country living on skin prick tests, immunoglobulin E and asthma in adults from the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyper-responsiveness and atopy.

BACKGROUND: Farming environment and traditional lifestyle seem to protect from childhood allergy. OBJECTIVE: The aim is to analyse the relationships of living in the country to asthma, positive skin prick tests and IgE among adults considering various windows of exposure over the life-span. METHODS: The study concerns 805 adults drawn from the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyper-responsiveness and atopy (EGEA) (asthmatic cases, non-asthmatic controls, and parents of cases with and without asthma). Ever living in the country concerned 55% of the subjects. Early (beginning < 1 years), childhood (beginning < or = 16 years), prolonged (duration > or = 10 years) and current life in the country were studied. RESULTS: The results based on the case control and family components of the study show that IgE levels were significantly lower in those who ever lived in the country and in particular in those who lived for > or = 10 years. Positive skin prick tests (SPT) were significantly less prevalent in those who ever lived in the country and in particular in those with childhood (< or = 16 years) exposure. These associations remained independent of age, sex, smoking or asthma with IgE levels of 64 vs. 88 IU/mL; P = 0.004 for those ever living in the country vs. others and odds ratio for SPT positivity of 0.72 (95% CI [0.53-0.98]). In the more specific group with traditional mode of heating in childhood (use of wood) associations were stronger. The association with asthma, studied in parents of asthmatic probands showed that fathers, but not mothers, of asthmatics were significantly less often asthmatic themselves in relation to country living. CONCLUSION: Country life protects from asthma and adulthood allergy. The protective effect is not restricted to exposure in early childhood.     

Prevalence of positive skin prick tests, allergic asthma, and rhinoconjunctivitis in teenagers in northern Sweden

The prevalence of positive skin prick tests (SPT) for common allergens and symptoms of allergic rhinoconjunctivitis or asthma was investigated in Umeå in northern Sweden in 1987. Skin prick tests with 10 allergens common in Sweden and a questionnaire were used to examine 1112 teenagers. All subjects with a positive skin prick test or symptoms were interviewed, and they were further investigated by a serum specific IgE test, a ventilatory lung function test, and a physical examination. At least one skin prick test was positive in 43% of the subjects. Ninety-three percent had at least one positive skin prick test to one of the three most common allergens: cat, timothy grass, and birch. The prevalence of current allergic rhinoconjunctivitis was 17%, current allergic asthma 2.8%, and current asthma (both allergic and nonallergic) 6.8%. Multiple logistic regression analysis showed that the most important risk factors for current asthma were sex (being a girl) and atopy. Heredity of asthma or rhinoconjunctivitis and being born in the winter (October-March) also increased the risk. In atopic subjects, having a mother who smoked and heredity of asthma increased the risk. For allergic rhinoconjunctivitis, heredity increased the risk of getting rhinoconjunctivitis.     

Growing disparities in atopy between the Finns and the Russians: a comparison of 2 generations

BACKGROUND AND OBJECTIVE: Western lifestyle has consistently been associated with the current asthma and atopy epidemics. We examined the occurrence and risk factors of atopy among schoolchildren and their mothers in 2 geographically adjacent areas with fundamental differences in living conditions and lifestyles. METHODS: A population-based study of 2 generations was carried out in eastern Finland and in western Russia. Randomly selected schoolchildren aged 7 to 16 years (367 in Finland and 446 in Russia) and their mothers (365 and 437, respectively) were enrolled. Data were obtained by using a modified International Study of Asthma and Allergies in Childhood questionnaire and by performing skin prick tests against 14 common airborne and food allergens. RESULTS: In children a 4-fold higher risk for atopy (> or =1 positive prick test result) was found in Finland compared with Russia. Sensitization rates in Finland were generally higher among children compared with those of their mothers, whereas in Russia the opposite trends emerged. Parental farming in early life (<1 year) in Finland (odds ratio [OR], 0.53; 95% CI, 0.28-0.99) and in Russia (OR, 0.47; 95% CI, 0.22-1.03) and currently in Finland (OR, 0.45; 95% CI, 0.22-0.91) conferred protection against atopy. Having pets, dogs in Finland (OR, 0.57; 95% CI, 0.35-0.95) and cats in Russia (OR, 0.43; 95% CI, 0.24-0.80), in early life was also inversely associated with atopy. CONCLUSION: Atopy was several-fold more common in Finland compared with in Russia, and disparities in sensitization rates between the countries have further increased during these generations. The similarity of explanatory variables of atopy in both countries suggests that determinants of atopy are shared, at least in similar geoclimatic conditions.     

New pregnancies and loss of allergy

BACKGROUND: Inverse associations between allergic disease and sibship have been consistently described and are frequently explained by purported lower rates of early infection among children from small families. Alternative explanations include the possibility that pregnancy itself determines maternal atopic status. OBJECTIVE: To test the hypothesis that atopy defined by skin prick test (SPT) declines with increasing numbers of pregnancies. METHODS: At enrollment to a birth cohort, mothers were skin prick tested to three common allergens. Seven years later these women underwent a second SPT and provided information on their reproductive histories. At both visits, information on allergic disease was also sought. RESULTS: Twenty five (15%) women who were initially atopic were no longer so at the second visit; loss of hayfever symptoms was reported by 33 (29%) women. Women with higher numbers of intervening pregnancies were more likely to 'lose' their atopy (P=0.05) and symptoms of hayfever (P=0.02); this was not true for asthma. The findings could not be accounted for by maternal age. CONCLUSION: Successive pregnancies may in part determine a mother's atopic state. Since maternal atopy is a risk factor for childhood atopic disease, this process may affect the atopic state of successive children. These findings suggest an alternative explanation for the sibship effect in allergic disease.