My daughter is omnivorous - truly. She might crunch up her nose at the first taste of potato-zucchini puree, but keys, newspapers, crushed rock...mmm, yummy! I draw the line at dry dog droppings, but generally I am not the patron saint of sanitised environments.

I stopped sterilising her dummy long ago, and these days I only wash it at the sink if the silicon nipple has been in direct contact with the floor. (Thank you, NUK, for designing dummies so that is rarely the case.)

I wash my hands when coming in from outside, after using the bathroom and before handling food, and that’s about it. And I let Rada crawl all over the living room, even though that means she’s getting a good taste of the floor and any object - clean or not - she can get hold of.

I am aware that sometimes other mothers judge me as unreasonably relaxed when it comes to hygiene, but I do believe some dirt is good for my baby. So I felt reassured when a few days ago, a friend emailed me a link to an article in The New York Times, titled Babies Know: A Little Dirt Is Good for You.

It quotes Mary Ruebush, a microbiology and immunology instructor, who wrote in her new book, "Why Dirt Is Good" (Kaplan): that "What a child is doing when he puts things in his mouth is allowing his immune response to explore his environment.

Not only does this allow for ‘practice’ of immune responses, which will be necessary for protection, but it also plays a critical role in teaching the immature immune response what is best ignored."

Researchers now think that organisms like the millions of bacteria, viruses and especially worms that enter the body along with "dirt" spur the development of a healthy immune system. Several continuing studies suggest that worms may help to redirect an immune system that has gone awry and resulted in autoimmune disorders, allergies and asthma.
 It seems that while improved hygiene helped the developed world rid of many deadly illnesses, taken to an extreme, it can be responsible for the significant rise in autoimmune disorders, such as multiple sclerosis, type 1 diabetes, asthma and allergies.

So while Rada discovers the world with her mouth, I keep thinking how the typical human probably harbours about 90 trillion microbes. The very fact that we have so many microbes of so many different kinds is what keeps us healthy most of the time. And now I’m off to run her dummy under hot water.