A genome-wide search for linkage to asthma. German Asthma Genetics Group

Asthma is among the most frequent chronic diseases in childhood. Although numerous environmental risk factors have already been identified, the basis for familial occurrence of asthma remains unclear. Previous genome screens for atopy in British/Australian families and for asthma in different American populations showed inconsistent results. We report a sib pair study of a sample of 97 families, including 415 persons and 156 sib pairs. Following an extensive clinical evaluation, all participants were genotyped for 351 polymorphic dinucleotide markers. Linkage analysis for asthma identified four chromosomal regions that could to be linked to asthma: chromosome 2 (at marker D2S2298, P = 0.007), chromosome 6 (around D6S291, lowest P = 0.008), chromosome 9 (proximal to D9S1784, P = 0.007), and chromosome 12 (D12S351, P = 0.010). These linkage regions could be reproduced for all loci by analysis of total or specific immunoglobulin E (minimum P values at these regions were 0. 003, 0.001, 0.010, and 0.015, respectively).

IgE screening in 1701 newborn infants and the development of atopic disease during infancy

IgE screening was done using the Phadebas IgE PRIST technique on the cord blood of 1701 newborn infants. Of these 8.3% developed obvious or probable atopic disease, predominantly atopic dermatitis and bronchial asthma, during the first 18 months of life. Of infants with a family history of atopic disease 10.5% developed such illness; the corresponding figure for infants with an initially high IgE concentration was 70%. Atopic disease developed in 73% of infants with a high IgE concentration in cord blood and a family history, but in only 3% of infants with a low IgE and no family history. A high IgE concentration in cord blood was associated with a high IgE and a positive radioallergosorbent test at between ages 18 and 24 months more often than was a low initial IgE level, indicating that in man as in animals there are high and low IgE responders already genetically coded at birth. IgE screening in cord blood is recommended if there is obvious atopy in both parents or if severe atopic disease if present in a sibling or in one parent.

Symptoms of bronchial hyperreactivity and asthma in relation to environmental factors

A questionnaire study regarding airway morbidity in children and environmental factors was performed in April 1985. The parents of 5301 children, aged 6 months to 16 years, from different rural areas in mid Sweden were sent a validated questionnaire and 4990 (94%) responded. The cumulative prevalence of bronchial hyperreactivity was 9.7% and of allergic asthma 5.2%. Children living near a paper pulp plant more often had symptoms suggesting bronchial hyperreactivity (124 (13.0%), relative risk 1.3) and allergic asthma (68 (7.1%), relative risk 1.3). In children living in a damp house problem bronchial hyperreactivity was found in 76 (19.0%) (relative risk 1.9) and allergic asthma in 35 (8.7%) of the children (relative risk 1.9). Children living in a damp house with parents who smoked had the highest figures: bronchial hyperreactivity was found in 44 (23.5%) (relative risk 2.8) and allergic asthma in 22 (11.6%) (relative risk 2.5). The results indicate that various moderate environmental pollutants may act synergistically to increase bronchial hyperreactivity and allergy especially in children with a family history of allergy.

Allergy prevention by maternal elimination diet during late pregnancy--a 5-year follow-up of a randomized study

The 209 mothers to be, enrolled in a randomized, prospective, allergy-prevention study from allergy-prone families, totally abstained from cow's milk and egg from gestational week 28 to delivery. This article presents the development of allergic disease at 5 years of age in their children, compared with the development of allergic disease in the children of the control mothers who took normal food throughout pregnancy. The prevalence of allergic disease could be evaluated in 198 children (95%). Allergic disease was monitored with questionnaires, skin prick testing, serum-IgE determinations, and physical examination. Eczema, allergic rhinoconjunctivitis, and asthma was equally common in the groups. Persistent food intolerance to egg was significantly more common in children of the mothers receiving the diet. This long-term follow-up confirms our previous findings that maternal elimination diet during late pregnancy does not prevent the development of allergic disease in the genetically predisposed child.

Atopic disease in seven-year-old children. Incidence in relation to family history

The incidence of atopic disease and its relation to the family history was studied by questionnaire in 1325 children, 7 years of age. A higher incidence of bronchial asthma (2.7%) was found than in a previous Swedish study. The total incidence of atopic disease in the children was 15.1% with a higher level when there was a double parental history of such disease (42.6%) as compared with a single such history (19.8%). When both parents had an identical type of atopic disease, i.e. respiratory or skin, the incidence of atopic disease was higher (72.2%) than when non-identical types occurred in the parents (20.8%). The findings support theories of a polygenic transmission of atopic disease as well as a genetic influence on symptom specificity in such disease and may be of value in genetic counselling.

Effect of maternal avoidance of eggs, cow's milk and fish during lactation upon allergic manifestations in infants

Atopic/allergic manifestations and skin-prick tests (SPT) to egg white, cow's milk (CM) and fish were evaluated during the first 18 months of life in two matched groups of infants with a family history of atopy/allergy. In one group (n = 65) the mothers had a diet free from eggs, CM and fish during the first 3 months postpartum, whereas the mothers in the other group (n = 50) consumed an ordinary diet. The diet of the infants was similar in both groups, i.e. CM was not supplied until 6 months of age, and eggs and fish not until 9 months of age. The incidence of atopic dermatitis was significantly lower in the maternal diet group during the first 6 months postpartum (10.8 and 28%, respectively) but not after that age. Other atopic/allergic manifestations did not differ and the number of positive SPT to egg white, CM or fish at 9 months of age was similar in both groups.

A double-blind, multicenter immunotherapy trial in children, using a purified and standardized Cladosporium herbarum preparation. I. Clinical results

A double-blind histamine placebo controlled immunotherapy trial was performed to investigate the clinical effect of a purified and standardized Cladosporium herbarum allergen preparation. Thirty children with a clinical history suggesting mould-induced asthma and/or rhinoconjunctivitis were included. The diagnosis was confirmed by positive skin prick test and Phadebas RAST as well as positive bronchial and/or conjunctival provocation test to Cladosporium herbarum. Immunotherapy was given for 10 months in a double-blind manner to randomized groups with either Pharmalgen/Cladosporium herbarum preparation or histamine placebo. Allergic side effects to injections were common, especially during the peak of the mould season (July-September in Scandinavia). In the active group, 13/16 patients experienced general reactions during the first 10 months of treatment. After 6 months of treatment, eye, nose and bronchial symptom scores and peak expiratory flow rates were similar for the groups, maybe because most of the children were also sensitive to many other allergens, including Alternaria alternata. However, medication scores were significantly lower in the treated group (P less than 0.01). Bronchial (P less than 0.01) and conjunctival sensitivity (P = 0.01) were significantly reduced in the Cladosporium-treated group but not in the placebo group after 10 months of treatment. This is the first double-blind clinical trial showing the clinical efficacy of immunotherapy in children with mould-induced asthma.

Appearance of atopic disease in relation to serum IgE antibodies in children followed up from birth for 4 to 15 years

BACKGROUND

Few studies have addressed the relationship between sensitization and the development of atopic disease over many years.

OBJECTIVE

To study the temporal relationship between the appearance of IgE antibodies in serum and atopic disease, we studied 324 children from three different groups, who were followed up prospectively from birth for 4, 12, and 15 years, respectively.

METHODS

Serum samples were obtained at various ages and analyzed for IgE antibodies against egg white, cow's milk, wheat, animal dander, house dust mite, birch and timothy with Phadebas RAST (Kabi Pharmacia Diagnostics AB, Uppsala, Sweden) or Pharmacia CAP system. In addition, a screening test for atopy, the Phadiatop Paediatric test (Kabi Pharmacia Diagnostics AB) was performed. Presence of atopic disease was assessed by means of clinical examination, interviews, and questionnaires.

RESULTS

In 135 children IgE antibodies were detected at least once to at least one allergen. Antibodies to egg white appeared in 46 children before or at 2 years of age: in 57% of them IgE antibodies to inhalants developed within the next 2 years, and in 19 of 25 (76%) IgE antibodies to inhalants developed before or at 12 to 15 years. Antibodies to inhalant allergens appeared in 55 children during the first 4 years of life and in 64 before 12 to 15 years. Among the former 48% and among the latter 32% had previously detectable egg white antibodies. Atopic disease appeared before or at age 4 years in 80% of the 40 children with IgE antibodies against egg white up to 9 months of age and in 69% of the 58 children who had a positive Phadiatop Paediatric test result in infancy.

CONCLUSIONS

IgE antibodies in children are usually associated with current or later topic disease. Sensitization to foods in infants is usually associated with appearance of IgE antibodies to inhalants later in life.

Soy versus cow's milk in infants with a biparental history of atopic disease: development of atopic disease and immunoglobulins from birth to 4 years of age

Forty-eight children with a biparental history of atopic disease were followed from birth to 4 years of age. One group was fed soy and the other cow's milk from weaning to 9 months of age. Two-thirds of the children developed symptoms of atopic disease with no significant difference between the groups. No difference was found in the serum immunoglobulins (IgE antibodies, IgA, IgG and IgM) during the observation period. The soy fed children showed transiently lower levels of IgG antibodies to cow's milk but higher levels of IgG antibodies to soy protein. Six children showed cow's milk intolerance and a further five had symptoms possibly related to the use of cow's milk. Withholding cow's milk during the first 9 months did not reduce the incidence of symptoms of cow's milk intolerance from birth to 4 years of age. Thus, no benefit was found from replacing cows' milk with soy. A prolonged breast feeding seems most rational for infants at risk of developing atopic disease, even if the present study did not show evidence of a prophylactic effect of breast milk against the development of atopic disease.

Predictive value of high IgE levels in children

A group of 207 healthy non-atopic children 0-14 years of age without any known family history of atopic disease was selected for a study of the relation between serum IgE levels and the occurrence of atopic manifestations during an observation period of 18 months; 206 fullfilled the study. Serum IgE was measured by a direct radioimmunological sandwich technique (PRIST). At the follow-up 28 of 32 with an initial IgE level greater than one standard deviation above the mean for the age continued to show a high level (87.5%). The total concordance was 81.1%. Atopic or probable atopic diseases had developed in 75.0% of children 0-1 year of age with an initial IgE above +1 S.D., but in only 6.4% of those from the same age group with a lower initial IgE. Even among children 2-14 years old, it was noticement of atopic disease. Otitis media was more frequent among children with an initially elevated IgE level than among the rest of the children. Determination of serum IgE with the PRIST-technique has been shown to provide a valuable means for predicting future atopic manifestations and may be used as a screening procedure especially in children of atopic parents.

Extensively and partially hydrolysed infant formulas for allergy prophylaxis

The allergy preventive effect of extensively (N) and partially (PH) hydrolysed cows' milk formulas compared with a regular formula (RM) was assessed in 155 infants with a family history of allergy. No cows' milk was given during the first nine months of life and no egg and fish up to 12 months of age. Breast feeding mothers avoided the same foods. At weaning the infants were randomised to one of the formula groups. The cumulative incidence of atopic symptoms at 18 months was 51, 64, and 84% in the N, PH, and RM groups, respectively. From 6 to 18 months there were significantly less cumulative atopic symptoms in the N group compared with the RM group, and significantly less than the PH group up to 6 (N = 25%; PH = 46%) and 9 months (N = 34%, PH = 58%). At 9 months significantly fewer infants in the N group (10%) than in the PH group (33%) had a positive skin prick test to eggs. The findings support an allergy preventive effect of an extensively hydrolysed formula, but not of a partially hydrolysed formula, during the first 18 months of life of high risk infants.

Natural history of bronchial asthma in childhood. A prospective study from birth up to 12-14 years of age

In a cohort of 1654 consecutively born children followed from birth, the cumulated incidence of asthma up to 11 years was 5.3% and the prevalence 3% between 10 and 11 years of age. The asthma début was prior to 1.5 years in 1/3 and before 3 years in 1/2 of the children. Among 59 children examined at 11.5-14.5 years of age, 16 (27%) had no prevalent asthma. On the other hand, inadequate medication was found in 13, undiagnosed chest deformity in four, and wheezing in seven children. All 54 tested children including those with no prevalent asthma had a PC20 histamine less than 8 mg/ml. Tread mill test gave a significant reaction in 15 children. Animal danders and pollens were the most common allergens giving reactions at skin prick test. Compared to one earlier Swedish study an increase in mite sensitivity was found. Cord-blood IgE concentration and a positive immediate family history of atopic disease had no predictive value for the severity of asthma at this follow-up. A new total asthma score including number of days with functional impact of asthma during the last year and present medication was used for group comparisons. Children with a high score at 11.5-14.5 years had more exercise-induced asthma, more concomitant allergic diseases, earlier asthma start, more chest deformity, hyperreactivity both on tread mill and histamine challenge tests, elevated IgE, positive Phadiatop and more reactions at skin prick test, especially to animals and mites. Bronchial asthma was found more often in children born during August through October, possibly due to unsuitable indoor climate and more virus infections during their first 6 months of life. The severity of the asthma was, however, not influenced by the month of birth. No significant differences were found between boys and girls regarding the age at début, asthma severity at follow-up, or bronchial histamine threshold levels.

Development of atopic disease in babies whose mothers were receiving exclusion diet during pregnancy--a randomized study

In a prospective, randomized study, we have monitored the effect of maternal abstention from cow's milk and egg on the development of atopy in babies. Two hundred twelve women were followed from midpregnancy. We report the occurrences of allergies in their babies up to 18 months of age, as assessed by skin prick testing, determination of serum IgE, questionnaires, and blinded physical examination by a pediatric allergist. Whatever the method that was used, there was no statistically significant difference between babies whose mothers received the "diet" or the "nondiet." Other factors known to influence the risk of atopy like heredity, sex, month of birth, breast-feeding, and exposure to tobacco smoke, animal dandruff, and solid food did not differ between the groups. The mothers receiving the exclusion diet, by their own choice, had diminished their intake of milk and egg during lactation also, and therefore, their babies were significantly less exposed to cow's milk before 6 months. Still, atopy was equally abundant among their children. Thus, maternal elimination diet during late pregnancy did not protect the baby against allergy.

A randomized controlled trial of the effect of pertussis vaccines on atopic disease

BACKGROUND

Pertussis vaccination in infancy has been suggested to increase the risk for development of asthma and allergy.

OBJECTIVE

To assess sensitization rates and development of atopic diseases in a prospective randomized controlled trial of pertussis vaccine.

PATIENTS AND METHODS

A total of 669 children were randomized to 1 of 4 vaccine groups (2-component acellular pertussis, 5-component acellular pertussis, whole-cell pertussis vaccines, and placebo [diphtheria and tetanus toxoids]). Diphtheria and tetanus toxoids were also given to the children in the pertussis vaccine groups. The children were evaluated by means of questionnaires at age 2 months, 7 months, and 2 1/2 years; skin prick tests at age 7 months and 2 1/2 years; and blinded clinical investigation at age 2 1/2 years. The families were contacted at regular intervals to assess possible adverse effects after the vaccinations and symptoms of whooping cough.

RESULTS

The cumulative incidence of atopic diseases was 30% and incidence rates were similar in the 4 groups after adjusting for family history. Exposure to environmental tobacco smoke and home dampness did not confound these results. The frequency of adverse effects did not differ appreciably between atopic and nonatopic children, with the exception that a nodule at the vaccination site was more frequent after whole-cell pertussis vaccination in the nonatopic children. Among 47 children with proven pertussis, atopic disease appeared in 19 (40%). Of these 47 children, 9 (19%) developed asthma, as compared with 58 (9%) noninfected children (P=.03).

CONCLUSIONS

We found no support for a drastic increase in allergic manifestations after pertussis vaccination. There was a positive association between whooping cough and asthma by 2 1/2 years of age. There seems to be little reason to withhold pertussis vaccination from infants, irrespective of family history of allergy.

IgE and atopic allergy in newborns and infants with a family history of atopic disease

Serum IgE levels were studied in 2 groups of children with a family history of atopic disease, 30 in whom the mother only and 38 in whom both parents had atopic disease. IgE antibodies were determined with Phadebas RAST Test and serum IgE with Phadebas IgE Test and Phadebas PRIST at 0, 3, 9, 12 and 18 months of age. There was no correlation between the serum IgE levels in mothers and their newborns. RAST tests were frequently positive in maternal sera but no positive RAST test was found in the newborns. Obvious and probable atopic disease developed during the observation period in 42.1% of the children with a double family history of atopic disease. In 75% of these the serum IgE level was above the upper limit of normal on an average 6 months before the onset of atopic symptoms. An elevated IgE level without atopic symptoms during the observation period occurred in only one child. It is concluded that the serum IgE in newborns seems to be of foetal origin and that the determination of serum IgE in infants is of value in predicting atopic allergy.

Immune response of the atopic woman and foetus: effects of high- and low-dose food allergen intake during late pregnancy

The influence of the mother's consumption of cows' milk and hens' egg on the immune response (IgE, IgG) in the mother and foetus was studied in 165 pregnant women with atopical respiratory disease with an allergy to pollen and/or animal dander. The women were randomly allocated to four diets ranging from a diet free from hens' egg and cows' milk to a diet containing intake of one egg and one litre of milk daily during the third trimester. No significant differences in cord blood IgE levels were noted in spite of differences in maternal diet, and no specific IgE antibodies to ovalbumin, ovomucoid and betalatoglobulin were found in the cord blood. The mother's IgG antibody concentrations to ovalbumin, ovomucoid and betalactoglobulin were influenced by her diet, but cord blood IgG antibody levels to the selected food allergens were unaffected. The data presented on the IgE and IgG antibody levels to ovalbumin, ovomucoid and betalactoglobulin in cord blood suggest that changes in maternal diet during the last trimester of pregnancy in order to prevent atopic sensitization in utero are less likely to affect the foetus than previously supposed.

Exposure to indoor allergens in early infancy and sensitization

BACKGROUND

Indoor allergens play a major role both in sensitization and as triggers of asthma in children. The relationship between allergen exposure and sensitization to cats, dogs, and mites was studied prospectively in 100 newborn babies with a history of allergy in both parents.

METHODS

Skin prick tests were done with Dermatophagoides pteronyssinus, D.farinae, and cat and dog allergens in all the children at 6 and 18 months of age and in 86 children at 5 years of age. Dust samples were collected from the homes during infancy and at 5 years. The parents of the children responded to a questionnaire focused on environmental factors that could influence indoor allergen levels. In addition, dust samples were collected from the day-care centers of the sensitized children. The allergen levels were determined by ELISA.

RESULTS

The levels of the major cat allergen, Fel d 1, varied from 0.02 microg to 6.8 microg/gm (geometric mean [GM], 0.4 microg/gm) during infancy and less than 0.02 microg to 13 microg/gm dust (GM, 0.12 microg/gm) at age 5 years. Dog allergen, Can f 1, levels ranged from 0.18 microg to 590 microg/gm (GM, 3.1 microg/gm) in infancy and 0.09 microg to 13 microg/gm at age 5 years (GM, 0.6 microg/gm). Eleven children (13%) were sensitive to cats, and three were sensitive to dogs at 5 years of age. They had been exposed to similar levels of allergen as the nonsensitized children. The levels of mite allergen (Der p 1 + Der f 1) at age 1 year varied from less than 0.02 microg to 1 microg/gm dust (GM, 0.12 microg/gm) and at age 5 years from less than 0.02 microg to 3.5 microg/gm (GM, 0.05 microg/gm) dust. Only two homes contained mite allergen levels greater than 2 microg/gm dust. The levels were less than 0.3 microg/gm dust in all but one sample from the day-care centers. Only one child was sensitized to mites at age 5 years. The mite allergen level was less than 0.1 microg/gm at home, and he did not attend a day-care center.

CONCLUSIONS

The findings indicate that exposure to low levels of indoor allergens in early childhood is associated with a low incidence of sensitization. However, levels well below currently suggested threshold levels may cause sensitization in children with a family history of allergy. We suggest that a fixed threshold risk level for allergic sensitization may not be appropriate in all climates.

Mite allergens in relation to home conditions and sensitization of asthmatic children from three climatic regions

We investigated the levels of mite (Der p I and Der f I) allergen in dust from bedrooms, living rooms, kitchens, and bathrooms from 130 homes of asthmatic children in three climatic zones of Sweden. Bedroom dust samples included the child's mattress, carpets, floors, and other plain surfaces. Living-room dust samples were taken from sofas and other furniture, carpets, floors, and other plain surfaces. The allergen levels were related to home characteristics, including absolute indoor humidity (AIH), relative humidity (RH), and air changes per hour (ach). Mite allergen was detected in 62% of the homes. Levels of Der p I varied between < 16 ng and 50 micrograms/g dust, and Der f I between < 16 ng and 73 micrograms/g dust. Because we have designed a composite type of dust collection in our study, the allergen levels found tend to average down the results. Mite allergen levels were higher in homes with dampness problems, in homes with a smoker, and in homes without a basement. Homes with high absolute humidity (> or = 7 g/kg) or relative humidity (> or = 45%) and poor ventilation (< 0.5 ach) contained higher levels of mite allergens than homes with lower humidity and better ventilation. However, the number of ach measurements in homes was not high, and few homes had > 0.5 ach. Sensitization to house-dust mites was more common in southern than in northern and central Sweden. High levels of house-dust mite allergen in a temperate climate where mites are not ubiquitous are thus associated with dampness problems in homes and with tobacco smoking. Our data confirm and extend previous findings that high AIH and RH and poor ventilation increase the risk of mite infestation in homes. It seems to be important and necessary to control indoor humidity and ventilation levels, to avoid high mite allergen exposure in a temperate climate, because 34% of mite-sensitized asthmatic children were exposed to levels of mite allergen < 2 micrograms/g dust in their homes. The study also shows that mite allergen levels below the suggested threshold level (2 micrograms/g dust) are associated with mite sensitivity in children with perennial symptoms of asthma.

Hypoallergenicity of an extensively hydrolyzed whey formula

Several different protein hydrolysate-based infant formulas have been promoted as hypoallergenic and considered suitable for the dietary management of cow's milk allergy (CMA). Accepting that none of the hydrolysate-based products is completely safe, the American Academy of Pediatrics (AAP) recommends that these formulas should be tested in a double-blind placebo-controlled setting and tolerated by at least 90% of children with proven CMA. In principle, this recommendation is also endorsed by the European Society of Paediatric Gastroenterology and Nutrition (ESPGAN) and the European Society of Paediatric Allergy and Clinical Immunology (ESPACI). In this two-center study, 32 children with proven CMA were tested with the extensive hydrolysate whey formula Nutrilon Pepti, for comparison with Profylac (extensive) and Nan HA (partial) whey hydrolysate products. Skin-prick tests (SPTs) were, respectively, positive to the three hydrolysate formulas in 19%, 15%, and 32% of children. After oral challenge it was concluded that 97% (95% CI: 85-100%) of the children tolerated Nutrilon Pepti, 94% (95% CI: 75-100%) tolerated Profylac, and 64% (95% CI: 37-81%) tolerated Nan HA. This study demonstrates that the extensive hydrolysates Nutrilon Pepti and Profylac are well tolerated in a population of children with proven CMA and that both products can be considered safe for their intended use. This study confirms that a very small number of children react even to extensively hydrolyzed formulas. SPT prior to oral exposure to the hydrolysate-based formulas can indicate whether a child is at risk of showing reactions to the product. Introduction of new products to these children should be carried out under a doctor's supervision. However, the majority of the SPT-positive children did tolerate the two extensively hydrolyzed whey-based formulas tested.

Comparison of IgE values as determined by different solid phase radioimmunoassay methods

Accurate measurement of low IgE concentrations if technically difficult. In this paper results obtained by a direct sandwich and three inhibition methods of radioimmunoassays are compared. For values above 50 U/ml good correlation was obtained with all methods. Below 50 U/ml, however, the inhibition methods tended to yield falsely high values. For very low concentrations, 1--10 U/ml the best correlation was obtained between the direct sandwich test (PRIST) and the inhibition test using a correction factor to allow for the non-specific effect of serum. The four methods were used to quantify IgE in cord serum samples from healthy individuals. The mean value obtained by PRIST was 0-4 U/ml and by the inhibition test, using a correction factor, 0-6 U/ml respectively. Because of its greater simplicity the direct sandwich test is recommended.

Maternal abstention from cow milk and egg in allergy risk pregnancies. Effect on antibody production in the mother and the newborn

To study the possibility of intrauterine sensitization, 212 women were enrolled on a voluntary basis into a prospective, randomized study, comparing the effects of an elimination diet and normal food during late pregnancy. The diet group took no cow milk and no egg from week 28 to delivery, and extra calcium and casein hydrolysate (Nutramigen) supplement was given to fill the nutritional needs of mother and child. The control group took normal food, including approximately 1/2 liter of milk/day and 3-5 eggs/week. All families had a history of allergy in mother, father, or sibling. Maternal weight gain during pregnancy was significantly lower in the diet group. Birth weights showed no significant difference between the two main groups, but smokers in the elimination diet group had significantly smaller babies. IgE antibodies to cow milk and egg were significantly higher in atopic than in non-atopic women before the trial. The diet caused a significant fall in IgG-antibodies to cow milk and egg in both atopic and non-atopic subjects. Cord blood IgE determination revealed no significant difference between the groups. No IgE antibodies to cow milk or egg were detected in any of the cord sera. The participating babies are being followed up until 18 months of age.

Season of birth as predictor of atopic manifestations

The relation between month of birth, sensitisation, and manifestations of atopy was assessed in 209 children who were followed from birth to 12-15 years. Children born during the tree pollen season were less likely to develop allergic rhinoconjunctivitis, IgE antibodies to pollen, or a positive screening test for IgE antibodies (odds ratio 0.28, 0.41, 0.35, respectively) than children born during the rest of the year. The prevalence of IgE antibodies to food and animal dander at 9 months and to atopic disease was higher in children born in the autumn and winter, that is, September to February, compared to the spring and summer (egg 20% v 6%; milk 10% v 2%). Thus sensitisation to pollen and allergic rhinoconjunctivitis is least common in children born in the spring, while birth in September to February is associated with an increased incidence of sensitisation to food and of atopic disease.

Bronchial asthma and acid reflux into the distal and proximal oesophagus

The prevalence of pathological gastro-oesophageal reflux in children and adolescents with asthma was studied by 24 hour two level oesophageal pH monitoring in 42 subjects aged 9-20 years with moderate or severe bronchial asthma. The importance of oesophagobronchial nerve reflexes and of aspiration of gastric acid as triggers in asthma was assessed by studying whether episodes of reflux into the distal and into the proximal oesophagus were followed by asthma attacks. Twenty-one subjects (50%) had a pathological total reflux time in the distal oesophagus and six (16%) in the proximal oesophagus. Nine patients had pathological gastro-oesophageal reflux into the distal oesophagus together with symptoms of asthma during the day on which the recording took place. In three of them the episodes of asthma symptoms were significantly correlated with preceding episodes of reflux into the distal oesophagus, and in one subject to reflux into the proximal oesophagus. We conclude that pathological gastro-oesophageal reflux is common in children and adolescents with asthma, but it seems to provoke symptoms of asthma in only a few. Symptoms of asthma were more often elicited by exposure of the distal oesophagus to gastric acid, possibly by a vagal reflex, than by aspiration of gastric juice.

Childhood asthma and exposure to indoor allergens: low mite levels are associated with sensitivity

The prevalence and level of sensitivity to indoor allergens were studied in relation to current exposure at home in 124 children with perennial asthma living in three climatic zones of Sweden. The house dust mite (HDM) allergen levels were higher in the South than in the North (p < 0.001), while cat and dog allergen levels tended to be higher in the North than the South (n.s.). Thirty-four percent of the children were sensitive to the HDM Dermatophagoides pteronyssinus, as determined by IgE antibodies in vitro, 27% were sensitive to D. farinae, 57% to cat and 55% to dog. Sensitivity to HDM was significantly more prevalent in Southern, than in Central and Northern Sweden (p = 0.001) where the children were more often sensitive to pets (cat p = 0.005, dog p = 0.002). A significant association between the concentration of Der p I and Der fI in the house dust and both the prevalence of sensitivity to HDM and the IgE antibody levels against mites was found even at concentrations well below the commonly suggested risk level for sensitisation of 2 micrograms/g dust. No relationship was found between pet allergen concentration in the home dust and sensitivity to pets, possibly because of exposure outside home, e.g. in schools and meeting places for leisure activities. Similarly, there was no consistent association between the level of mite or pet allergen exposure at home and asthma severity as judged by symptom and medication score. The study indicates that there is no threshold value for sensitisation to mite allergens in asthmatic children, and therefore, dust allergen levels at home should be kept as low as possible in homes of children at risk for asthma.