In terms of health? Yes, very much so.. they believe that our over obsession with germs is responsible for a generation of children who are actually weaker and less resilient to germs than we were. They have linked this to an increase in childhood asthma and allergies.. they have considered giving kids injections of germs and dirt to try to build an immune system.. and they say that having pets or living on a farm actually makes for healthier kids than those who are raised in cities without exposure to dirt and germs..
The thing to remember is that however hard we try we cannot eliminate entirely dirt or germs.. and perhaps we shouldnt try..
If you are talking about a messy or not super clean home.. well again.. perhaps it's unnatural to have a home that is pristine.. i do remember when i was a kid that my fav places to go were homes where they weren't too fussy and the kids were free to play and make a mess and where you weren't afraid to touch anything
ABSOLUTELY. It's scientifically established that small children/toddlers build their immune systems by injesting "dirt" as a matter of growing up - including sucking their thumb.
(Just saw daydream above who has posted re this topic).