I meet so many mothers who won’t let their children walk barefoot in the house or the park, won’t let them touch snails, won’t let them grasp mud or go out in the hot rain of the monsoon, won’t let them near any animals and refuse to keep a pet because it might bring in bacteria.

Their children wear socks throughout the year, have no idea what a plant is, apart from the cut flowers they see in vases at home. And they are sicker than most children.

For decades paediatricians warned mothers that if they wanted their children allergy free they should keep animals out of the house.

By the early 2000s, a number of studies showed the opposite, that exposure to pets in the very early stages of life provides protective benefits and prevents the development of allergic rhinitis, asthma and eczema. Of the nine studies analyzed in 2011, six detected lower levels of IgE antibodies and 15 to 21 percent less eczema in children who had been exposed to cats or dogs as soon they were born.

Allergies have been on the rise since the 20th century. Even in a country where nutrition levels are higher, like the USA, 8-10 per cent of children have asthma, according to the Centers for Disease Control and Prevention. Asthma is a chronic lung disease that inflames and narrows the airways. It causes recurring bouts of wheezing, chest tightness, shortness of breath, and coughing. Conventional wisdom says that reducing allergenic substances at home will help lessen asthma symptoms.

However the Urban Environment and Childhood Asthma (URECA) study, funded by the National Institute of Allergy and Infectious Diseases (NIAID), points in the opposite direction: that exposure to certain allergens and bacteria early in life, before asthma develops, may protect children from asthma. Since 2005, URECA has tracked newborns who are at high risk for developing asthma, because at least one parent has asthma or allergies, for 7 years. Their findings were published in 2017, in the Journal of Allergy and Clinical Immunology.

Of the 442 children, 130 (29%) had asthma at age 7. The children who didn’t have it had, strangely enough, higher levels of cockroach, mouse, and cat/dog bacteria in the dust samples, collected from the children’s homes, during the first 3 years of life starting at 3 months.

“Our observations imply that exposure to a broad variety of indoor allergens, bacteria early in life may reduce the risk of developing asthma,” says URECA principal investigator. The microbes that pets carry into the home from outdoors, could mature baby’s developing immune system and train it to fend off assaults from allergens. Researchers at Kuopio University Hospital in Finland, writing in the journal Pediatrics, say that babies who grow up in homes with a dog or a cat – have a lower risk of allergies than children who live pet-free. Their study found that living with household dust from homes with a dog, prevented infection with a common respiratory virus that is thought to increase the risk of childhood asthma.

The researchers followed 397 children, born in Finland between 2002 -5, and found that babies who grew up in homes with pets were 44% less likely to develop an ear infection and 29 per cent less likely to receive antibiotics, compared with pet-free babies. Overall, babies who lived with a dog were 31% more likely to be healthy in their first year than babies without a dog; kids from homes with cats were 6% more likely to be healthy than those in cat-free families. The study found that children with pets were healthier overall. But this varies: the children who grew up with indoor dogs only, had more infections that than those whose dogs went out every day, suggesting that when animals are allowed to bring in more dirt and microbes from outdoors, it helps strengthen babies’ immune systems faster. Research at the University of Alberta, published in the journal Microbiome, shows infants exposed to dirt and bacteria from furry family pets, especially dogs, showed much higher levels of two types of gut microbes associated with lower risks of obesity and allergic disease.

746 infants, in the Canadian Healthy Infant Longitudinal Development Study between 2009-2012 also showed that those who grew up with dogs had lower rates of asthma and more diverse groups of microbes in their guts. The study also suggests having pets in the house could reduce the chances of a mother passing on a strep infection during birth, which can cause pneumonia in newborns.

Scientists at the University of San Diego Knight Lab, which is doing one of the largest studies on microbes in humans, has found that living with dogs provides the body protective benefit. Nearly a thousand species of microbes live inside the human gut and they play an important role in the health of the human by bolstering the immune system. Each species has a different impact and, without exposure to a diversity of bacteria, the body doesn’t learn how to differentiate between dangerous and harmless bacteria. This theory has emerged after more than a dozen studies showed that children born into families with significant farm animal exposure had fewer instances of asthma and allergies, compared with those that had no exposure to farm animals.

In a 2010 study, done in the University of California, researchers discovered that homes with dogs had a far greater abundance of bacteria than those with no pets. The scientists then researched on whether the dog microbe rich house dust would protect mice against allergens. It did. In 2016, the scientists went ahead to examine the faeces of 308 babies less than a year old. The results, published in Nature Medicine, showed that babies with the highest risk of developing allergies and asthma lacked dog exposure.

In the latest study, scientists from the University of Gothenburg, Sweden looked at another angle: if having more than one pet would increase the benefit.

They looked at data from two previous studies. One of them had tracked 1,029 children from infancy to age 8. 49 per cent children, who had not had pets at home during their first 12 months of life, had allergies. This fell to 43 per cent in children who, as babies, had lived with one pet, and 24 per cent for children who had lived with three pets. Two of the children had lived with five pets – neither of them had allergies.

In another study, tracking 249 children from birth to 9 years of age, the rate of allergies was 48 per cent for children with no pets in their first year, 35 per cent for children with exposure to one pet, and 21 per cent for children who had lived with two or more pets. This proves that more exposure to pets means more immunity Studies have found that children who grow up on a farm with livestock have a lower risk of allergies.

Can exposure to animals help pregnant women’s growing babies? A 2009 study in Europe showed that the umbilical cord blood in pregnant women with farm exposure had more active neonatal immune cells. This means that the microbes in the pregnant mother are doing something positive for the child.

We’ve known for years that dogs were good for our mental health. Now there is clear proof that those health benefits go even deeper. Pets prevent allergies. Exposure to an animal increases the baby’s immunity. The more cats or dogs you live with as an infant, the less your chances of getting asthma, hay fever and eczema, to name a few diseases.