151 the authors of the new book let them eat dirt saving your child from an oversanitized world say keeping children too clean shields them from certain microbes that are essential for a healthy immune system so children should be allowed to get dirty when they play the books authors b brett finlay and marieclaire arrieta draw upon evidence that suggests allowing children to get dirty exposes them to healthy germs that can actually be good for them if we miss out on that exposure the immune system is not going to mature arrieta an expert in microbes and immunology said in an interview with abc news failure to develop the immune system puts children at higher risk for asthma diabetes and even obesity the authors said classroom experiment reveals just how quickly germs can spread finlay and arrieta say one of the best ways for children to get those essential microbes is for them to play in dirt children especially those who are under 5 years old should be allowed to play outside and get dirty but within limits they added we do have to think a bit let the kid lick the floor in your own house but not the subway station finlay a microbiology professor at the university of british columbia in canada said the authors also say its okay that parents allow other people to touch their newborns and its also okay to let the family dog lick the baby a dog will come and lick you and your kids thats good arrieta said they are basically bringing in the outdoors into your home the authors also say children dont have to wash their hands after being outside and that parents shouldnt panic if their babys pacifier falls on the floor put it in your own mouth dont wash it studies show thats beneficial in reducing asthma and obesity in children finlay said this is a little much for melissa willets a selfdescribed germophobe who has three daughters i worry about what they touch and then put their hands in their mouth or their eyes she said of her children who are eight five and three years old willets chronicled her germ fears for a blog on babycentercom you dont want to put your kids in a bubble thats not healthy for them either but its hard not to want to protect them from germs she said