“Having pets growing up makes you less allergic or nonallergic to them.” That phrase was once considered an old wives’ tale. Nowadays, researchers are proving it to be true.
The devil is in the details such as when you have pets growing up, how many pets, and what type of pet you have. Even though contradictory studies have stated otherwise, the preponderance of evidence suggests that not only can pets make a person less allergic to them, but they also protect against multiple allergens. This becomes an even more compelling reason for families to share their lives with companion animals when combined with their well-established psychological, longevity, and health benefits.
Research is not stopping at allergenic reactions regarding the positive and negative effects of dogs or cats living in the home. But, first, let’s look at allergies and asthma.
Allergies and Asthma
A large study followed children born in the Detroit area between 1987 and 1989. At six years of age, the researchers performed a skin prick test to check for atopic sensitivity and an allergen-specific blood antibody IgE test. IgE is an antibody affected by seasonal and environmental allergen exposures. The results were amazing. The researchers concluded that exposure to 2 or more dogs or cats in the first year of life may reduce subsequent risk of allergic sensitization to multiple allergens during childhood.
A follow-up study was conducted when the children reached the age of 18. The researchers determined that males – who lived with an indoor dog during the first year of life – had half the risk of being sensitized to dogs at age 18 compared with those who did not have an indoor dog in the first year of life. Additionally, teens with an indoor cat in the first year of life had half the risk of being sensitized to cats at age 18 compared to those who did not have an indoor cat in the first year.
While the study did not prove lifetime desensitization to cats and dogs in the entire population that lived with pets the first year of life, the study showed that pets provided a protective barrier against other allergens during the earlier years of life.
Another researcher, Bill Hesselmar, has been looking into this for over 20 years and confirmed the results. His team’s 2018 study concluded, “The prevalence of allergic disease in children aged 7–9 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-farm’ effect, whereby cats and dogs protect against allergy development (asthma, allergic rhinoconjunctivitis, or eczema).”
Indeed, studying the “farm” effect has taken off in the last few years. A 2016 landmark study focused on asthma by comparing Amish of Indiana and Hutterite children of South Dakota who lived on farms in the United States. The researchers did not expect to find any differences between the two groups as they have similar lifestyles.
For instance, both groups came to the United States during the 18th and 19th centuries, and have lived relatively isolated when compared to the majority of Americans that became assimilated. The Amish came from Switzerland and the Hutterites from Austria. Their lifestyles are similar with respect to most of the factors known to influence the risk of asthma, including large sibship size, high rates of childhood vaccination, diets rich in fat, salt, and raw milk, low rates of childhood obesity, long durations of breast-feeding, minimal exposure to tobacco smoke and air pollution, meticulously clean homes, and no indoor pets.
The key difference is how both groups farm. The Amish practice traditional farming, live on single-family dairy farms, and use horses for fieldwork and transportation. The Hutterites live on large, highly industrialized, communal farms.
Remember, both communities forbid pets in the home and they are fastidious. The research team took measurements of the indoor air and collected dust. Common allergens – such as cats, dogs, house-dust mites – were detectable in airborne dust from 4 of 10 Amish and 1 of 10 Hutterite homes. In contrast, endotoxin levels were measurable in airborne dust in all of the houses. Yet, the median allergen levels were strikingly higher in Amish homes than in Hutterite homes.
The researchers were shocked by the bloodwork results. The Amish children had a large proportion of newer neutrophils — white blood cells that are part of the innate immune system. These children’s neutrophils were newly emerged from their bone marrow, which is evidence of a continual low-grade reaction to microbial invaders.
The Hutterite children had less neutrophils and those neutrophils were older. In contrast, their blood had increased levels of another type of immune cell, eosinophils, that are known to provoke allergic reactions.
So, the prevalence of asthma in Amish children was only 5.2% compared to Hutterite children at 21.3%. In terms of allergic sensitization, the results were also comparably different. The Amish was at 7.2% versus 33.3% in Hutterite children.
To provide a balanced summary, however, some study results conflict with the findings mentioned above. In 2011, a study conducted by the University of Cincinnati stated that dog ownership significantly reduced the risk for eczema at age four among dog-sensitized children. However, cat ownership combined with cat sensitization significantly increased the risk.
What about prior to birth?
Researchers from the Detroit study evaluated 675 children between the ages of two and four for atopic dermatitis.
If the mother lived with indoor pets during pregnancy, the risk of atopic dermatitis was lower among those children – most significantly with indoor dogs only or indoor dogs and cats prenatally. However, a similar effect did not appear among 75 mothers with cat only prenatal exposure.
The Gut’s Impact on Allergies and Other Diseases
We often think of the gut as a separate and distinct entity from the rest of the body. Yes; we know it is the main conduit to getting essential vitamins and proteins, but we forget that the gut needs to be balanced to ensure this delivery mechanism, and that recent studies have documented the critical effects of the gut microbiome (microbial content) on metabolism, the immune system, brain health and behavior.
Furthermore, we are just discovering how this balance – conveyed by beneficial microbiota (good bacteria) in the gut – affects and protects against allergies and obesity.
A study from Canada showed the impact of pets – both pre- and postnatally – on infant gut microbiota. While the authors point out the numerous factors that come into play such as – caesarean sections or antibiotic use – they came to a resounding conclusion: The impact of pet ownership and exposure to furry pets increased the abundance of two beneficial bacteria, Ruminococcus and Oscillospira, which help stave off childhood atopy and obesity.
One scenario that struck us involved mothers who were given a prophylactic antibiotic during vaginal delivery labor. Doctors typically give this to help prevent the passing of Group B Streptococcus from mother to child through the vagina. Most babies born to women carrying this bacterium are healthy. But the few who are infected by group B Strep during labor can become critically ill.
Regardless, antibiotic prophylaxis is a major disruptive of microbiota exposures.
This study found that the infants – who were vaginally born to mothers treated with antibiotics – had reduced amounts of fecal Streptococcaceae, if they were exposed to pets prenatally. Bear in mind, that no other factors like the number of siblings or breastfeeding could explain this – the only difference was in pet exposure.
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