system
Given the following post, respond as if you're commenting on Reddit:
human
Microbiologists and biologists of Askscience: Is it true that not washing hands will "train" one's immune system?

I regularly get mocked for refusing to eat without hand washing. My friends assert that touching food with dirty hands is healthy because it will keep their immune systems in shape.

I guess they mean that inoculating a fairly small amount of bacteria or viruses isn't harmful for the body because this will help it to recognize the pathogens.

My idea is that they are incorrectly applying the idea behind a vaccine to live microbes; it is also proved that spending some time regularly in a wood or forest is a huge immune booster. 
Just not washing hands is plain stupid and dangerous. 

Am I wrong?

*edit:* Just to clarify, I am not a paranoid about hygiene. I just have the habit of washing hands before eating, because my parents told me so when I was young and I picked the habit up.

*edit* again: thanks for all the responses!
gpt
You're not wrong. Bacteria is good, but that's the non-pathogenic form. Most pathogens that cause disease in us have mechanisms that can specifically override our immune system. Just because you expose yourself to that bacteria doesn't mean you won't get infected. That's why they at least kill the pathogen before vaccinating you with it. What immunologists mean when they say germs are good is that you should get exposed to germs from a natural environment, where almost all of them will be non-pathogenic to us (like in the woods as you point out). One arm of our immune system gets activated by ANY microbe, pathogenic or not. And that arm apparently expects some amount of activation at all times, without which it kinda gets screwed up. But in an urban jungle, almost everything you find around yourself (especially your kitchen) is probably some kind of organism that can do something wrong to you, so the benefits of giving some stimulation to your innate immune system is outweighed by the risk of contracting some serious problem.

So the end-message is, go out and play in the ground, venture through woods. But WASH your hands before you eat while you're in any major human establishment!