Impacts of Dogs on Childhood Allergy and Asthma: What Research Reveals

Based on the results of six studies, it is shown that for children who are not sensitive to dog allergens in their early years, dog ownership can protect against asthma. In addition, three studies found that early exposure to dogs can reduce the odds of being sensitive to fur or airborne allergens. For children who have started to show sensitivity to dog allergens or symptoms of asthma, exposure to dog allergens and owning a dog does not protect them from asthma, but is rather associated with asthma (or subsequent asthma). However, whether removal of the dog can improve the symptoms is uncertain because the dog allergen (dander) may still be present in the home after the dog has left.  

Created on November 21 2015 at 08: 00 AM


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Pros

References:

1: "Direct And Indirect Exposure To Petsrisk Of Sensitization And Asthma At 4 Years In A Birth Cohort," Clinical & Experimental Allergy , 2003, by C Almqvist, AC Egmar, G Hedlin. (Citations: 140).

INTRODUCTION: There are conflicting data on the association between early exposure to pets and allergic diseases. Bias related to retrospective information on pet ownership has been addressed as a reason for distorted study results. OBJECTIVE: To elucidate how early exposure to cat and dog relates to IgE-sensitization and asthma in children at 2 and 4 years of age, in a prospective birth-cohort study. METHODS: Four thousand and eighty-nine families with children born 1994-1996 in predefined areas of Stockholm answered questionnaires on environmental factors and symptoms of allergic disease at birth, one, two and four years of age. Dust samples collected from the mothers' beds at birth were analysed for Fel d 1 and Can f 1 in a subgroup of the cohort. Blood samples taken at four years from 2614 children were analysed for allergen-specific IgE to common airborne allergens. Risk associations were calculated with a multiple logistic regression model, with adjustment for potential confounders. RESULTS: A correlation was seen between allergen levels and reported exposure to cat and dog. Exposure to cat seemed to increase the risk of cat sensitization, OR (odds ratio) 1.44 (95% confidence interval 1.03-2.01), whereas dog exposure did not have any effect on dog sensitization, OR 1.16 (0.79-1.72). Dog ownership was related to a reduced risk of sensitization to other airborne allergens, OR 0.36 (0.15-0.83), and a similar tendency was seen for cat ownership OR 0.63 (0.37-1.07). Early dog ownership seemed to be associated with a lower risk of asthma, OR 0.50 (0.24-1.03), with no corresponding effect after cat ownership, OR 0.88 (0.56-1.38). CONCLUSION: Early exposure to cat seems to increase the risk of sensitization to cat but not of asthma at 4 years of age. Dog ownership, on the other hand, appears to be associated with lowered risk of sensitization to airborne allergens and asthma. Both aetiological relationships and selection effects have to be considered in the interpretation of these findings.


2: "Does Pet Ownership In Infancy Lead To Asthma Or Allergy At School Age? Pooled Analysis Of Individual Participant Data From 11 European Birth Cohorts," , 2012, by KCL Carlsen, S Roll, KH Carlsen, P Mowinckel. (Citations: 70).

Objective To examine the associations between pet keeping in early childhood and asthma and allergies in children aged 6–10 years. Design Pooled analysis of individual participant data of 11 prospective European birth cohorts that recruited a total of over 22,000 children in the 1990s. Exposure definition Ownership of only cats, dogs, birds, rodents, or cats/dogs combined during the first 2 years of life. Outcome definition Current asthma (primary outcome), allergic asthma, allergic rhinitis and allergic sensitization during 6–10 years of age. Data synthesis Three-step approach: (i) Common definition of outcome and exposure variables across cohorts; (ii) calculation of adjusted effect estimates for each cohort; (iii) pooling of effect estimates by using random effects meta-analysis models. Results We found no association between furry and feathered pet keeping early in life and asthma in school age. For example, the odds ratio for asthma comparing cat ownership with “no pets” (10 studies, 11489 participants) was 1.00 (95% confidence interval 0.78 to 1.28) (I2 = 9%; p = 0.36). The odds ratio for asthma comparing dog ownership with “no pets” (9 studies, 11433 participants) was 0.77 (0.58 to 1.03) (I2 = 0%, p = 0.89). Owning both cat(s) and dog(s) compared to “no pets” resulted in an odds ratio of 1.04 (0.59 to 1.84) (I2 = 33%, p = 0.18). Similarly, for allergic asthma and for allergic rhinitis we did not find associations regarding any type of pet ownership early in life. However, we found some evidence for an association between ownership of furry pets during the first 2 years of life and reduced likelihood of becoming sensitized to aero-allergens. Conclusions Pet ownership in early life did not appear to either increase or reduce the risk of asthma or allergic rhinitis symptoms in children aged 6–10. Advice from health care practitioners to avoid or to specifically acquire pets for primary prevention of asthma or allergic rhinitis in children should not be given.


References:

1: "Exposure To Pets, And The Association With Hay Fever, Asthma, And Atopic Sensitization In Rural Children," Allergy, 2005, by M Waser, E Von Mutius, J Riedler, D Nowak, S Maisch. (Citations: 97).

Background:  An increasing number of studies report pet exposure to be associated with lower risk of asthma and allergies. This ‘protective pet effect’ has been suggested to result from a modified T-helper (Th)2-cell response, or because of increased microbial load in homes where pets are kept. We examined the associations between pet contact and the occurrence of asthma and allergies in children of the rural Allergy and Endotoxin (ALEX) population, taking farm animal contact, endotoxin and cat allergen levels in mattress dust into account. Methods:  Information about contact with pets and farm animals, asthma and allergy were collected for 812 children by a standardized parents’ questionnaire and an interview. Mattress dust endotoxin and cat allergen levels as well as specific IgE and IgG4 antibodies to Fel d1 were determined. Results:  Current contact with dogs was inversely associated with diagnosed hay fever (OR 0.26, 95% CI 0.11–0.57), diagnosed asthma (OR 0.29, 95% CI 0.12–0.71), sensitization to cat allergen (OR 0.48, 95% CI 0.23–0.99) and to grass pollen (OR 0.55, 95% CI 0.33–0.94), but not with increased IgG4 levels. Early and current contact with cats were associated with reduced risk of wheezing (OR 0.48, 95% CI 0.23–1.00, and OR 0.49, 95% CI 0.26–0.92, respectively) and grass pollen sensitization. Adjustment for farm animal contact but not for endotoxin and cat allergen exposure attenuated these associations and the effect of pet was stronger among farmers’ children. Conclusion:  Although pet exposure was very frequent in this rural population, the inverse relation between current dog contact, asthma and allergy was mostly explained by simultaneously occurring exposure to stable animals or was restricted to farm children. In addition, a subtle form of pet avoidance may contribute to the protective effect of pet.


References:

1: "Does Early Exposure To Cat Or Dog Protect Against Later Allergy Development?," Clinical and experimental allergy: journal of the British Society for Allergy and Clinical Immunology , 1999, by B Hesselmar, N Aberg, B Aberg, B Eriksson. (Citations: 531).

BACKGROUND: It is unknown which factors in modern western society that have caused the current increase in prevalence of allergic diseases. Improved hygiene, smaller families, altered exposure to allergens have been suggested. OBJECTIVES: To assess the relationship between exposure to pets in early life, family size, allergic manifestations and allergic sensitization at 7-9 and 12-13 years of age. METHODS: The prevalence of allergic diseases and various background factors were assessed in 1991 and 1996 by questionnaire studies. In 1991, the study comprised representative samples of children from the Göteborg area on the Swedish west coast (7 years old, n = 1649) and the inland town Kiruna in northern Sweden (7-9 years old, n = 832). In 1992, a validation interview and skin prick test (SPT) were performed in a stratified sub-sample of 412 children. In 1996, this subgroup was followed up with identical questions about clinical symptoms as in 1991, detailed questions about early pet exposure were added and SPT performed. RESULTS: Children exposed to pets during the first year of life had a lower frequency of allergic rhinitis at 7-9 years of age and of asthma at 12-13 years. Children exposed to cat during the first year of life were less often SPT positive to cat at 12-13 years. The results were similar when those children were excluded, whose parents had actively decided against pet keeping during infancy because of allergy in the family. There was a negative correlation between the number of siblings and development of asthma and allergic rhinitis. CONCLUSION: Pet exposure during the first year of life and increasing number of siblings were both associated with a lower prevalence of allergic rhinitis and asthma in school children.


2: "Direct And Indirect Exposure To Petsrisk Of Sensitization And Asthma At 4 Years In A Birth Cohort," Clinical & Experimental Allergy , 2003, by C Almqvist, AC Egmar, G Hedlin. (Citations: 140).

INTRODUCTION: There are conflicting data on the association between early exposure to pets and allergic diseases. Bias related to retrospective information on pet ownership has been addressed as a reason for distorted study results. OBJECTIVE: To elucidate how early exposure to cat and dog relates to IgE-sensitization and asthma in children at 2 and 4 years of age, in a prospective birth-cohort study. METHODS: Four thousand and eighty-nine families with children born 1994-1996 in predefined areas of Stockholm answered questionnaires on environmental factors and symptoms of allergic disease at birth, one, two and four years of age. Dust samples collected from the mothers' beds at birth were analysed for Fel d 1 and Can f 1 in a subgroup of the cohort. Blood samples taken at four years from 2614 children were analysed for allergen-specific IgE to common airborne allergens. Risk associations were calculated with a multiple logistic regression model, with adjustment for potential confounders. RESULTS: A correlation was seen between allergen levels and reported exposure to cat and dog. Exposure to cat seemed to increase the risk of cat sensitization, OR (odds ratio) 1.44 (95% confidence interval 1.03-2.01), whereas dog exposure did not have any effect on dog sensitization, OR 1.16 (0.79-1.72). Dog ownership was related to a reduced risk of sensitization to other airborne allergens, OR 0.36 (0.15-0.83), and a similar tendency was seen for cat ownership OR 0.63 (0.37-1.07). Early dog ownership seemed to be associated with a lower risk of asthma, OR 0.50 (0.24-1.03), with no corresponding effect after cat ownership, OR 0.88 (0.56-1.38). CONCLUSION: Early exposure to cat seems to increase the risk of sensitization to cat but not of asthma at 4 years of age. Dog ownership, on the other hand, appears to be associated with lowered risk of sensitization to airborne allergens and asthma. Both aetiological relationships and selection effects have to be considered in the interpretation of these findings.


Cons

References:

1: "Quantitative assessment of exposure to dog (Can f 1) and cat (Fel d 1) allergens: relation to sensitization and asthma among children living in Los Alamos, New Mexico," Journal of Allergy and Clinical Immunology, 1995, by Ingram, J. M., Sporik, R., Rose, G., Honsinger, R., Chapman, M. D., & Platts-Mills, T. A.. (Citations: 307).

Background: Our objective was to identify the allergens associated with asthma among schoolchildren in an area of the United States where dust mite growth is expected to be poor. Los Alamos, N.M., was chosen because it has low rainfall and is at high altitude (7200 feet), making it very dry. One hundred eleven children (12 to 14 years old) from the middle school who had been previously classified according to bronchial hyperreactivity to histamine (BHR) were studied. Methods: Sera were assayed for IgE antibodies to mite, cat, dog, cockroach, Russian thistle, and grass pollen, with both CAP system fluoroimmunoassay (Kabi Pharmacia, Uppsala, Sweden) and conventional RAST. Allergens were measured in dust samples from 109 homes with two-site assays for mite (Der p 1 and Der f 1), cat (Fel d 1), dog (Can f 1), and cockroach (Bla g 2). Results: Concentrations of dog and cat allergens were elevated in almost all houses with pets but were also high in a significant proportion of the houses without pets. Levels of mite allergen were less than 2 μg/gm in 95% of the houses, and cockroach was undetectable in all but two of the houses. Among the 21 with BHR who had symptoms, 67% had IgE antibody to dog and 62% had IgE antibody to cat. For these allergens IgE antibody was strongly associated with asthma (p < 0.001). By contrast, the presence of IgE antibody to mite, cockroach, or grass pollen was not significantly associated with asthma. Conclusion: The high prevalence of IgE antibody to cat and dog allergens among these children is in keeping with the presence of cat and/or dog allergen in most of the houses. Furthermore, sensitization (as judged by IgE antibodies) to cat and dog allergens was strongly associated with asthma. On the other hand, no clear relationship was found between sensitization or symptoms and the current level of allergen in individual houses. The results show that in this mite-and cockroach-free environment sensitization to domestic animals was the most significant association with asthma.


2: "Dog Hypersensitivity In Asthmatic Children," Acta Paediatrica, 1983, by T Vanto, A Koivikko. (Citations: 92).

ABSTRACT. The occurrence of dog hypersensitivity in 203 unselected asthmatic children was investigated by means of the skin prick test, the provocation test and RAST. The history of past and present exposure to dogs, symptoms in contact with dogs, and the effects of pet avoidance were examined. The amount of dog dander antigens was analyzed by counter-immunoelectrophoresis from dust samples from 67 homes. A history of past or present dog hypersensitivity was obtained from 120 subjects (59%). A positive (≧++) prick test reaction was observed in 113 (56%), a positive provocation test result in 84 (41%) and a RAST class ≧ 1 in 140 (69%). The serum levels of IgE antibodies to dog dander correlated significantly with serum total IgE and the frequency of asthmatic attacks. The occurrence of dog allergy was not significantly associated with past or present exposure to dogs at home. However, the children who were exposed to dogs during the first year of life had dog allergy more often than those with late or without exposure. Significant amounts of dog dander antigen were also found in dust samples from homes where dogs have never been kept. Serum samples from previous years were available from 24 patients. Rising or steadily high levels of IgE antibodies to dog dander were observed even in subjects who strictly avoided dogs. The results show that dog hypersensitivity is an important cause of allergic disorders in asthmatic children, and that the common presence of dog dander antigens in our environment may induce dog allergy even without direct exposure to dogs.


How

References:

1: "Predictors Of Asthma Three Years After Hospital Admission For Wheezing In Infancy," Pediatrics, 2000, by TM Reijonen, A Kotaniemi-Syrjnen, K Korhonen. (Citations: 140).

Objective. To evaluate the influence of early antiinflammatory therapy in the development of asthma 3 years after hospitalization for wheezing in infancy. In addition, the effects of allergic sensitization and respiratory syncytial virus (RSV) infection on the development of asthma were investigated. Design and Setting. A randomized, controlled follow-up study in a university hospital that provides primary hospital care for all pediatric patients in a defined area. Patients. Eighty-nine infants under 2 years of age who had been hospitalized for infection associated with wheezing and followed up for 3 years. Intervention. Early antiinflammatory therapy was given for 16 weeks; 29 patients received cromolyn sodium and 31 received budesonide. Twenty-nine control patients received no therapy. Outcome Measures. Clinical diagnosis of current asthma, defined as having at least 3 episodes of physician-diagnosed wheezing and either a wheezing episode during the preceding year or ongoing antiinflammatory medication for asthma. Results. Fourteen (48%) patients in the former cromolyn group, 15 (48%) in the former budesonide group, and 16 (55%) in the control group had current asthma. The significant predictors of asthma were age over 12 months (risk ratio [RR] 4.1; 95% confidence interval [CI] = 1.59–10.35), history of wheezing (RR 6.8; CI = 1.35–34.43), and atopic dermatitis on study entry (RR 3.4; CI = 1.17–9.39). Skin prick test positivity at the age of 16 months significantly predicted asthma (RR 9.5; CI = 2.45–36.72). In addition, all of the 18 (20%) children sensitized with furred pet developed asthma. RSV identification (RR 0.3; CI = 0.08–0.80) and early furred pet contact at home (RR 0.3; CI 0.10–0.79) were associated with the decreased occurrence of asthma. Conclusions. Antiinflammatory therapy for 4 months has no influence on the occurrence of asthma 3 years after wheezing in infancy. Early sensitization to indoor allergens, especially to pets, and atopic dermatitis predict subsequent development of asthma. RSV infection in wheezing infants may have a better outcome than other infections.



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Impacts of Dogs on Childhood Allergy and Asthma: What Research Reveals

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