Can a Baby Devlop an Allergy to Dogs After Being Around Them Since Born
PLoS I. 2018; 13(12): e0208472.
Pet-keeping in early life reduces the risk of allergy in a dose-dependent fashion
Bill Hesselmar
1 Department of Paediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, Academy of Gothenburg, Gothenburg, Sweden
Anna Hicke-Roberts
one Department of Paediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
Anna-Carin Lundell
ii Department of Rheumatology and Inflammation Research, Found of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
Ingegerd Adlerberth
3 Section of Infectious Diseases, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
Anna Rudin
2 Department of Rheumatology and Inflammation Research, Found of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
Robert Saalman
ane Department of Paediatrics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
Göran Wennergren
one Department of Paediatrics, Plant of Clinical Sciences, Sahlgrenska Academy, Academy of Gothenburg, Gothenburg, Sweden
Agnes E. Wold
three Department of Infectious Diseases, Institute of Biomedicine, Sahlgrenska University, University of Gothenburg, Gothenburg, Sweden
Lucienne Chatenoud, Editor
Received 2018 Sep 5; Accustomed 2018 Nov sixteen.
- Supplementary Materials
-
S1 Table: Cantankerous-Exclusive Cohort. (DOCX)
GUID: 3258A7AF-9B43-4D94-AEC0-151A398401A7
S2 Table: Nativity Cohort. (DOCX)
GUID: 881BEBC3-2C93-4A28-B0B8-E9AB54CA7E1E
S3 Tabular array: Cross-Sectional Cohort logistic regression. (DOCX)
GUID: 1A504C06-3920-4647-9222-C08C1CAEB4D7
S4 Table: Birth Accomplice logistic regression. (DOCX)
GUID: 94C1FF6E-37A2-4636-A932-5B00E00775BB
S5 Table: Birth Cohort OPLS. (DOCX)
GUID: 5D719B86-EE96-488E-AEE8-B379F0737B44
S6 Tabular array: Nascence Cohort parental sensitization. (DOCX)
GUID: 9F337580-E1EE-41BD-9840-5B6F41A5688E
- Data Availability Statement
-
All relevant data are within the manuscript and its Supporting Data files.
Abstract
Objectives
Several studies have indicated that early pet keeping could protect the infant from later allergy evolution. Here, we investigate if at that place is a dose-dependent association betwixt cat- and dog-keeping during the first year of life and subsequent allergy development.
Methods
Two cohorts were investigated: a cross-sectional questionnaire-based study of 7- to 8-yr-old children (North = 1029) from Mölndal and Kiruna, and a birth-accomplice of children from the Västra Götaland county clinically evaluated for asthma and allergy by paediatricians upwardly to the historic period of 8–9 years (North = 249). The cross-exclusive study asked validated questions on asthma and allergy that had been used in ii previous studies of children from the same areas. In the birth-cohort study, a diagnosis of asthma and allergy was based on predefined clinical criteria, and laboratory evaluation included blood eosinophils, pare-prick tests and specific immunoglobulin Due east analyses. Information on pets during kickoff year of life was collected retrospectively in the Cross-Sectional Cohort and prospectively in the Birth Cohort.
Results
A dose-response association was seen, with less allergic manifestations (any of asthma, allergic rhinoconjunctivitis, or eczema) with increasing number of household cats and dogs during the starting time year of life. In the Cross-Sectional Accomplice, allergy ever decreased from 49% in those with no pets to nix in those with five or more pets (P-value for trend 0.038), and from 32% to zero for allergy concluding yr (P-value for trend 0.006). The same design was seen in Birth Cohort. Sensitization to animals, as well equally pollens, also decreased with increasing number of animals in the household.
Decision
The prevalence of allergic illness in children aged vii–9 years is reduced in a dose-dependent fashion with the number of household pets living with the child during their first year of life, suggesting a "mini-subcontract" effect, whereby cats and dogs protect against allergy evolution.
Introduction
The clinical consequences of exposure to dissimilar allergens in early life have long been a matter of discussion, especially if infants are exposed to pets such equally cats and dogs during their beginning twelvemonth of life. Early pet-keeping was previously considered to be a gamble factor for allergy development, merely several studies from the final 20 years take highlighted that this is probably not the instance [one–8], even in individuals with a stiff family unit history of atopy [9]. Today, early on pet-keeping is mostly non considered to be a take chances gene for allergy in families with otherwise healthy infants.
Conversely, pet-keeping during early life may instead protect from later allergy [1], especially exposure to more than one domestic dog or to both a cat and a canis familiaris [three, 4]. We were the first to demonstrate, in 1999 [1], that children in families keeping (a) cat(southward) or (a) domestic dog(due south) during the child´s first year of life had less asthma at 7–9 years every bit compared to children with no such animals, and that this difference remained also after adjusting for selection mechanisms due to allergy among parents or siblings. The existence of an allergy-protective effect from pet-keeping is too supported by immunological data. In studies analysing the effect of cat exposure on asthma and allergy development, a high-dose exposure to cat allergens [ten], or keeping of cats [eleven], were associated with clinical tolerance and cat-specific IgG4, but not IgE.
Immunological tolerance facilitated by keeping of cats and dogs during early life is, still, still a hypothesis, despite some support for this supposition in the aforementioned studies. Not all studies report a long-term protective effect [vii], and if such an event exists, information technology is nonetheless non known how consecration of this immunological tolerance is mediated. In principle, nosotros hypothesized that two different mechanisms–not mutually exclusive–could contribute to a protective effect of pet-keeping. First, exposure to cat or domestic dog dander, containing massive amounts of allergens from the respective species, could induce high-dose clinical tolerance to the allergens, i.e. reduced risk of true cat-allergy in the children exposed to cats and dog-allergy in children with dogs. Second, cohabiting pet animals could provide a "mini-farm" environment, with microbes or other immunoregulatory factors that provide a broad modifying effect on immune evolution in the child, leading to tolerance not only to the pet itself, only also to food and airborne allergens. In this study we try to address this question, hypothesising that high-dose allergen exposure should induce tolerance only to that specific type of beast, whereas a mini-subcontract induced tolerance is supposed to be protective not only to a specific animal but also to other environmental allergens.
Most often research focus on identifying adventure factors for allergy development. Merely in modernistic society, finding lifestyle factors that could protect from allergy has become equally important. The principal aim of this study was to investigate if pet-keeping during early life affects later allergy development and, if so, whether a dose-response clan was detectable. Second, if the protective effect was species-specific, suggesting an allergen-driven tolerance induction, or, if it is species-unspecific suggesting an allergy-protective "mini-farm" environment. We used data from a cross-sectional cohort and a birth cohort for the analyses to minimize influences from mutual methodological shortcomings, e.g. selection bias and reverse causation.
Methods
The analysis was based on ii study populations. A cross-sectional questionnaire study was performed in 2007 in 7–8 year old children (Cantankerous-Sectional Accomplice, N = 1029). The other written report population was the Birth Cohort, recruited between 1998 and 2007.
Cantankerous-Sectional Accomplice
In the cantankerous-sectional cohort, a questionnaire on asthma and allergy was distributed to all 7- to 8-year-old children in Mölndal, a small town which is function of the Gothenburg urban surface area on the South West Sweden, and Kiruna, a town in the far north of Sweden. Of 1838 questionnaires distributed, 1029 (56%) were returned. We used the same questions on asthma, eczema, and allergic rhinoconjunctivitis (ARC) as had been used in two previous studies of children from the same regions and of similar ages in 1979 and in 1991 [12, thirteen]. Diagnostic criteria and information gathered on pet exposure are shown in Tabular array 1.
Tabular array 1
Diagnostic criteria and information on pet exposure in the Cross-Sectional Cohort and Birth Cohort.
| Criterion | Cross-Exclusive Cohort | Nascence Cohort |
|---|---|---|
| Diagnosis of asthma | "Asthma e'er" diagnosed if in that location was a positive response to: "Has your child had asthma or asthmatic bronchitis"? "Current asthma" diagnosed if there was a positive response to "Has your child had asthma or asthmatic bronchitis in the previous twelvemonth"? | Asthma diagnosed at historic period 8–nine years if the child in the last 12 months had symptoms of wheeze/heavy animate together with: FEV1 reversibility >12%, or bronchial hyperresponsiveness to methacholine (PD20 <0.six mg), or ongoing controller medication with inhaled corticosteroids or leukotriene adversary |
| Diagnosis of ARC | ARC diagnosed if there was a positive response to: "Has your kid had allergic rhinitis or allergic conjunctivitis"? "Electric current ARC" diagnosed if in that location was a positive response to: "Has your child had allergic rhinitis or allergic conjunctivitis in the previous year"? | ARC diagnosed at age viii–9 years if the child in the last 12 months had eye or nose symptoms suggestive of allergic disease together with a positive skin-prick test or specific IgE to the relevant allergen |
| Diagnosis of eczema | "Eczema ever" diagnosed if there was a positive response to: "Did your child ever have eczema"? "Current eczema" diagnosed if at that place was a positive response to: "Did your child have eczema in the previous year"? | Eczema diagnosed at age 8–9 years if the kid in the last 12 months had a peel condition fulfilling Williams criteria [16], or an itching dermatitis that had been chronic or relapsing for ≥half-dozen months |
| Diagnosis of allergy | "Allergy ever" and "allergy last year" included any of asthma, ARC, or eczema ever or last year, respectively | "Allergy last year" included any of asthma, ARC, or eczema |
| Cats and dogs in household | Number of cats and dogs in the household during the showtime year of life | Information on number of cats and dogs was obtained from the 6-month telephone interview |
Birth Accomplice
The Birth-Cohort was pooled data from two nascence-cohorts in the Västra Götaland county. Betwixt 1998 and 2003, 184 children in the ALLERGYFLORA were recruited from Mölndal in the Gothenburg urban area [xiv]. The ALLERGYFLORA was designed to analyse the furnishings of early life events and early on gut colonisation on later allergy development. The second grouping was the FARMFLORA. The report is a copy of the ALLERGYFLORA, simply the children are living in a rural region. Children were recruited between 2005 and 2007, from a farming area in Skaraborg, northeast of Gothenburg, comprising 28 children living on dairy farms and 37 children living in the same rural area but not on farms [15]. The parents were all contacted before the nascence, and children born ≥38 gestational weeks were included in the study on day 0–3 later delivery. The parents were interviewed when their children were aged vi and 12 months; clinical examinations by paediatric allergologists were done at age 18 months and 3 and 8–9 years. Diagnostic criteria and information gathered on pet exposure are detailed in Table i.
Lung function tests
Lung role tests were done in the Nativity Cohort. Earlier lung function tests, children were non permitted: tea, coffee, or cola drinks within 4 hours; brusque-acting beta-agonists within 8 hours; ipratropium bromide inside 24 hours; long-acting beta-agonists, theophylline, or nasal steroids within 48 hours; or antihistamines within 72 hours to ane calendar week, depending on the type of drug. Methacholine challenges were not performed during the pollen season in pollen-allergic children; if the child had a viral infection or mutual common cold within 14 days; if oral steroids had been given within xiv days; if forced expiratory volume in 1 due south (FEV1) was <65% predicted; or if the kid had a heart disorder. All lung office tests were done in a sitting position and a olfactory organ clamp was used.
Flow-volume curves and reversibility tests were performed in accordance with American Thoracic Society and European Respiratory Society guidelines [17] using Spida 5 spirometry software (Micro Medical Express, Rochester, UK). A bronchodilator response was considered positive if FEV1 increased by >12% from baseline [18].
Airway hyperresponsiveness was determined past direct methacholine challenge [19], using a tidal book-triggered dosimetric method (Spira Elektro ii jet nebulizer; Spira Respiratory Care Centre Ltd, Hämeenlinna, Finland). Basic FEV1 was determined after inhalation of isotonic saline. Methacholine was later inhaled in increasing doses at intervals of at least 1 infinitesimal until FEV1 had decreased by ≥twenty%, or a cumulative dose of 6.1875 mg had been given. At the end of the challenge, all subjects received an inhalation of salbutamol and FEV1 was measured to ensure recovery (FEV1 >ninety% of baseline value). The provocative dose inducing a fall of ≥20% in FEV1 (PDtwenty) was adamant by interpolating the dose-response bend; airway hyperresponsiveness was defined equally PD20 <0.six mg. The slope was calculated from the maximum fall in FEVane divided past the cumulative dose.
Eosinophils, specific immunoglobulin E, and Peel-prick tests
Blood tests and Skin-Prick Tests were done in the Birth Cohort. Blood eosinophil cells, specific immunoglobulin E (IgE), and total IgE were all analyzed at the Sahlgrenska Academy Hospital. All analyses were accredited past the Swedish Board for Accreditation and Conformity Cess. For specific IgE and full IgE, Phadiatop and ImmunoCAP tests were used (Thermo Fisher Scientific, Uppsala, Sweden). Pare-prick tests (SPTs) were carried out for common airborne allergens (cat, domestic dog, horse, rabbit, birch, grass, mugwort, Dermatophagoides pteronyssinus, Dermatophagoides farinae, and Cladosporium herbarum) according to the standards of the Subcommittee on Pare Tests of the European University of Allergy and Clinical Immunology [twenty]. Allergen extracts were all manufactured by ALK (Hørsholm, Kingdom of denmark). A positive SPT corresponds to a weal with a bore exceeding the negative command by ≥3 mm.
Statistical analysis
Analyses were performed with SPSS statistical software (version 24; IBM Corp., Armonk, NY, U.s.); for the multivariate analyses we used SIMCA-P+ software (version 14.1; MKS Umetrics AB, Umeå, Sweden).
χ2 tests were used to compare differences betwixt proportions. Tendency analyses were based on linear-past-linear clan and exact tests. Backward logistic regression models were used to control for covariates and possible confounders. A 2-sided P-value <0.05 was considered statistically significant.
Orthogonal project to latent structures (OPLS), an extension of PLS-regression (Partial Least Square regression) in order to improve interpretability, was used in the birth-cohort report to analyse the relationship betwixt the number of pets at vi months of historic period, parental history of allergy, and 12 independent outcomes from the follow-up at eight–9 years. B coefficients on scaled and centered data were calculated with 95% confidence intervals.
Ethics
Written informed consent was obtained from all parents. The written report was canonical by the Ethics Committee of the Academy of Gothenburg, Sweden (R448-97 and Ö 446–00) and the Human Enquiry Ethics Committee of the Medical Faculty, Academy of Gothenburg, Sweden (Dnr. 321–05, 363–05, 105–07 and 674–xiv).
Results
In both the Cross-Exclusive Cohort and the Birth Cohort, the sexual activity ratios were 50:l or shut to it (Tabular array 2). A parental history of allergy was slightly less mutual in the Birth Cohort, probably due to the stricter diagnostic criteria used requiring a doctor's diagnosis of allergic disease. In children, the prevalence of allergic disease (allergy terminal year) was similar in the Cross-Sectional Accomplice and the Birth Accomplice.
Table 2
Characteristics of the study populations.
| Cross-Sectional Cohort (northward = 1029) | Nascence Cohort (n = 249) | |
|---|---|---|
| Boys, n (%) | 483 (47) | 125 (fifty) |
| History of allergya, n (%) | ||
| Female parent | 498 (48) | 110 (44) |
| Father | 399 (39) | 90 (36) |
| Parent with a university caste, n (%) | ||
| Mother | 321 (31) | – |
| Father | 277 (28) | – |
| Number of pets | ||
| 0 | 767 | 181 |
| ane | 165 | 40 |
| 2 | 64 | – |
| ≥2 | – | 28 |
| 3 | 21 | – |
| 4 | 7 | – |
| ≥5 | 2 | – |
| Children with allergy, n (%) | ||
| Ever | 481 (47) | 95 (38) |
| In the last twelvemonth | 314 (31) | 73 (29) |
In the Cross-Sectional Cohort, allergy was based on a history of asthma, ARC, or eczema (allergy e'er), or, asthma, ARC, or eczema with symptoms in the last 12 months (allergy last twelvemonth). In the Birth Cohort, allergy ever was based on a diagnosis of asthma, ARC, or eczema at any of the follow-ups (18 months, 3 years, or 8–9 years), and allergy last year was based on electric current asthma, ARC, or eczema with symptoms in the 12-month period preceding the follow-upwards at age 8–ix years.
The number of household dogs and cats during first year of life was prepare to range from zero to ≥5 in the Cross-Sectional Cohort; in the smaller Birth Cohort, the number of pets at half dozen months of age was recorded in a range from null to ≥2.
Fig 1 shows the cumulative incidence (allergy e'er) and prevalence (allergy last twelvemonth) of allergic disease in relation to the number of household cats and dogs during the start yr of life for the Cross-Sectional Cohort. Both allergy ever and allergy terminal yr decreased with increasing number of cats and dogs (P-value for trend with exact examination: 0.006 for allergy ever and 0.038 for allergy last year).
Data from the cantankerous-sectional written report.
Allergy (whatsoever of asthma, allergic rhinoconjunctivitis, or eczema) in relation to the number of household cats and dogs during the kid's showtime year of life. Allergy terminal yr required current symptoms, i.e. symptoms in the last 12 months.
A like pattern was seen in the Birth Accomplice, with a decreasing frequency of allergic disease (both current and e'er) with increasing number of household cats and dogs (Fig ii; P-value for trend: 0.007 for allergy ever and 0.008 for allergy last year).
Information from the Nativity Accomplice.
Allergy (any of asthma, allergic rhinoconjunctivitis, or eczema) in relation to the number of household cats and dogs when the kid was 6 months former. Allergy last year required current symptoms, i.eastward. symptoms in the last 12 months.
Backward multiple logistic regression analyses, with allergy e'er every bit independent variable, were used on both the Cross-Sectional and Birth Cohort. In the Cross-Sectional Accomplice, contained variables were sex, parental history of allergy, number of siblings, and number of pets during first twelvemonth of life. In the final step, only pets and parental history of allergy remained, giving an odds ratio of 0.80 for every additional animal (P = 0.012). In the Birth Cohort, the same independent variables were included. In the final step, only pets during first yr of life and parental history of allergy remained, giving an odds ratio of 0.65 for each additional brute (P = 0.058).
To farther analyse a possible influence of parental allergic disease on the families' pick to have pets, parental sensitization was analysed in relation to number of household pets. In the first 184 Birth Accomplice-children from the Gothenburg-Mölndal area, parents were tested for sensitization with the Phadiatop test. Blood samples were obtained from 149 mothers and 141 fathers. In that location was no statistically pregnant difference in the frequency of positive Phadiatop tests from parents with no household pets when their child was six months former versus parents with increasing number of animals (Table 3).
Tabular array 3
Sensitisation in parents, measured with Phadiatop tests, in relation to the number of household cats and dogs the family unit had when their child was six months old.
| Number of cats or dogs when the child was 6 months quondam | Positive Phadiatop test result, n/N (%) | |
|---|---|---|
| Mother (n = 149) | Begetter (due north = 141) | |
| 0 | 65/127 (51) | 73/121 (lx) |
| i | 9/eighteen (50) | vii/17 (41) |
| ≥two | 3/4 (75) | 2/3 (67) |
| P-value for tendencya | 0.590 | 0.425 |
In the Nativity Cohort, the relationship between the number of household pets at half-dozen months former and sensitisation at 8–nine years erstwhile was tested in an OPLS analysis (Fig 3), a regression model suited to test how a large set up of Ten-variables relate to Y-variable(s). The number of pets was used as the Y variable (the left bar). The figure shows how the other variables (X variables) are related to the Y variable. Ten-variable bars in the same direction as the Y variable bar are positively associated; bars pointing in the reverse management to the Y-variable bar are negatively associated. The main finding was that the degree of sensitization in children, expressed as SPT bore, decreased with increasing number of pets, and that this association was seen not only for sensitization to pets just also for sensitization to pollen (birch and grass). No meaning association was constitute betwixt number of pets and presence of allergy in mother or begetter.
Orthogonal projection to latent structures loading plot showing associations between the number of household cats and dogs when the child was 6 months old (Y variable), and a set of xv X variables.
The outcome variables for lung role (forced expiratory volume in ane due south [FEV1]/forced vital capacity [FVC]), bronchial hyperresponsiveness (BHR), blood eosinophil count (B-Eos), percent of blood eosinophils (Eosproc), total immunoglobulin (IgE), and peel-prick tests (SPTs) were from the age 8–9 years follow-upwardly. SPTs are given as weal diameter. X variable confined pointing in the same direction equally the Y variable are positively associated with the Y variable, and confined pointing in the contrary direction are negatively associated. The height of the bars shows the B-coefficients for scaled and centered data, with 95% confidence intervals.
Word
In 1999 we published a study showing that early pet-keeping was associated with less allergy evolution in children [ane]. Since then, several studies accept been published supporting our finding [2–6, eight], simply others did not [7]. A common interpretation of published information has, to date, been that early keeping of cats or dogs does not increase the risk of allergy but we do non definitely know if information technology has whatever protective effect, in the same way every bit subcontract animals and farm-living have [21–23]. Nevertheless, the main findings from this extended study support our previous results, that pet-keeping during early on childhood is associated with less allergy, and that the protective result from pet-keeping increased with increasing number of animals. Furthermore, the protective effect influenced not but clinical allergy only also sensitization to both animals and pollen, suggesting an underlying "mini-farm" machinery.
In this study nosotros used results from two different study populations in gild to accost mutual questions raised when interpreting results from studies investigating allergy prevention. The first, and most obvious question is if the findings could be due to a blazon-1 error, i.e. a false positive. Every bit we found similar results in both populations studied, we argue that our primary finding was not due to a type-ane fault. Epidemiological cantankerous-sectional studies have several advantages as they commonly include a large population, making them suitable for both univariate and multivariate analyses, but other biases and diagnostic validity are always bug to exist considered. We used the Cross-Sectional Cohort for the main analyses, and these were and so repeated in the Birth Cohort. As the results from the Cross-Sectional Cohort were reproduced in the Birth Accomplice, we argue that neither recall bias nor reverse causation explain the results. Neither was diagnostic validity a major problem in the Cross-Sectional Cohort, as the main finding was repeated in the Nativity Cohort in which strict diagnostic criteria were used. A similar statement could as well exist used when assessing parental history of allergy. In the Cantankerous-Sectional Cohort, a healthy pet-owner effect might be an issue, simply in the Nativity Cohort the data on parental allergy was collected when the child was simply a few days old. Furthermore, parental sensitization data from the Birth Cohort does not indicate any major divergence in sensitization blueprint between parents with versus without pets. Selection bias is another issue oft discussed for this type of study, equally allergic parents are non supposed to own cats or dogs. One way to handle this effect is to ask parents about their reasons for not attributable pets, as nosotros did in our 1999 written report [1]. Another method is to conduct a dose-response analysis, as we have done in this study. The rationale behind this approach is that selection may occur between families having versus non having animals, rather than between having one or two animals versus two or three animals. To summarise, it is our view that selection bias, call back bias, contrary causation, or imprecise diagnostic validity do not explain our finding of an inverse correlation between the number of household cats and dogs during a kid'southward offset twelvemonth of life and allergy prevalence.
The dose-response outcome and a similar protective outcome for sensitisation to animals and pollen, betoken that the protective result is mediated by the keeping of animals, and is not a species-specific upshot. Information technology is our proffer that the allergy-protective effect mediated past pet-keeping should be considered equally a "mini-subcontract" effect, equating our findings to those found in the numerous farm studies performed [24]. A "mini-farm" effect could also explicate why a protective effect is plant in some studies, just non all. The effectiveness of an unspecific allergy-preventive (or immune-stimulating) agent should exist seen in the light of other protective factors. This was demonstrated elegantly by Matricardi et al, who showed that siblings only had an allergy-protective effect in subjects seronegative for hepatitis A and not in those who were seropositive, i.e. those who already had a strong allergy-protective consequence from hepatitis A or an environment where hepatitis A is common [25]. A dog or a cat may thus have a protective effect in children who have few other protective factors, provided that the kid has close contact with the animal during their early years. If the child already has several other protective factors, a dog or cat may not add any actress protection, unless the child is exposed to several animals, i.due east. a "mini-farm". Although several studies have shown that pet-keeping, mainly from direct exposure [26], in early on life is associated with less asthma or allergy [2–6, 8, 26], especially if exposed to more than than i animal [three, four], such an outcome is non found in all studies. In a big study with pooled data from several birth cohorts, neither a protective effect, nor an increased allergy run a risk from early on pet-keeping was found [7]. Nonetheless, non finding a protective outcome in a study population does not necessarily mean that a protective upshot does not be during certain circumstances, as previously mentioned. Protection seems more likely if exposure occurs at shut quarters, i.eastward. direct exposure [8], if other strong allergy-protective factors are missing, or, every bit in our study, if the kid is exposed to more than one creature [iii, 4]. Thus, it is plausible that tolerance induction via a mini-farm mechanism crave a close contact with the animal(s), otherwise the child will only exist exposed to allergens from the beast, not the microbes and endotoxins shred by the animal, components that seems to be of import in tolerance induction. And close contact with the pet animal is probably more common in urban areas, where families use to keep their pet animals inside the house or flat. In rural areas, dogs and cats are more oftentimes kept outdoors. In such cases, allergens from cats and dogs will still exist spread inside the house, causing sensitisation, but non the microbes and microbial products that follow a close contact with the animal. Cleaning habits may also affect the effectiveness of pet-induced tolerance induction. Allergens are seldom reduced past excessive cleaning [27], just the mini-farm environment might exist less constructive.
The mechanisms backside the proposed "mini-subcontract" effect from dogs and cats can, of course, but be speculated on, only according to the hygiene hypothesis [28], immune stimulation past microbial exposure might be 1 possible mechanism. We have institute support in various studies for allergy protection past early on microbial exposure [29, 30] or presumed early microbial exposure [31], and dogs and other pet animals seem to take this capability [8].
With the study design, nosotros accept been able to show a negative association betwixt the number of animals in the child's domicile during the first year of life and allergy evolution, but the written report has limitations. The Cross-Exclusive Cohort had a response rate of slightly less than 60%, which may select a more allergy-prone population, even though nosotros have not establish any indications for such a option [32]. Furthermore, call back bias and diagnostic validity may be limitations in cross-sectional questionnaire studies, simply these limitations are balanced by the concordant results found in the Birth Accomplice. Similarly, the smaller Birth Accomplice population is balanced past the much larger population size in the Cross-Sectional Accomplice.
In conclusion, the prevalence of allergic disease in children anile 7–9 years is reduced in a dose-response pattern with increasing number of cats and dogs in the dwelling during the starting time year of life, suggesting a "mini-farm" outcome whereby pet-keeping protects against allergy development.
Supporting information
S1 Tabular array
Cross-Sectional Accomplice.
(DOCX)
S2 Table
Birth Accomplice.
(DOCX)
S3 Tabular array
Cantankerous-Sectional Cohort logistic regression.
(DOCX)
S4 Table
Nascency Cohort logistic regression.
(DOCX)
S5 Table
Birth Cohort OPLS.
(DOCX)
S6 Table
Birth Cohort parental sensitization.
(DOCX)
Acknowledgments
The authors would like to thank school personnel and teachers in Mölndal and Kiruna for helping in the distribution and drove of questionnaires in the cross-exclusive study.
In the nativity-cohort study, the authors would like to thank all the children and families who took part in the report. Nosotros also want to thank the staff at the Delivery Ward, Mölndal Hospital, the study nurses Mainor Åmark, Helen Andersson, and Anders Nordberg, and pediatricians Susanne Johansen, Margareta Ceder, Gunhild Lindhagen, Stefan Stentoft, and Carl-Johan Törnhage. We also thank Ms Caroline Landon for her professional person and excellent work in editing and styling the manuscript.
Funding Statement
The studies were funded by the Sahlgrenska University at the University of Gothenburg; the Swedish Asthma and Allergy Association Research Foundation (BH); the Swedish Enquiry Council; the Vårdal Foundation; the European Commission (QLK4-2000-00538); the Torsten and Ragnar Söderberg Foundation; Gothenburg Medical Social club; the Cancer and Allergy Foundation; Swedish Research Quango for Environmental, Agronomical Sciences and Spatial Planning; the Ekhaga Foundation; Food and Health Concept Centre, Gothenburg, West Gothia Region; The study was also financed by grants from the Swedish land under the agreement between the Swedish government and the canton councils, the ALF-agreement (AR, AW, GW, IA). No one from the funding sources was involved in the blueprint, execution, or assay of the report. Anna Rudin reports that part of her salary for her university total professor position at The Sahlgrenska University at the University of Gothenburg is covered past grant from AstraZeneca IMed RIA (Respiratory Inflammation, Autoimmunity) in compensation for advice regarding bones research in inflammation at the company.
Data Availability
All relevant data are within the manuscript and its Supporting Information files.
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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6300190/
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