A coworker told me today that washing your hands too often, especially as a child, can result in a weakened immune system, because you aren't giving your body the chance to build up immunities. He used this as partial justification for not washing hands before eating, and said that he never washed his hands before eating while growing up. He isn't advocating to not wash your hands after using the bathroom (we agree that washing your hands after the going to the bathroom is important). A quick google search shows sites that agree that washing your hands too much can be harmful.
Does washing your hands too often weaken your immune system? By "weaken" I mean "make us more susceptible to getting sick" or " prevent the immune system from getting stronger." I'm not asking if washing hands actively attacks the immune system.
I am not asking if washing your hands too often is bad for the skin - I get very dry skin myself, and frequently use lotion after washing my hands.
I am also not asking if you should wash your hands before eating. Some of the questions I linked address that (TL;DR - you should wash your hands before preparing and eating food).
My question is very similar to Does living clean weaken ones immune system?. (The answer on that question is yes.) However, (1) That question was in 2012 - is there evidence to the contrary? (2) I'm not sure if this is a total duplicate.
Other similar questions:
Do hand sanitizers have a negative impact on the human immune system?
Does washing hands with soap remove more germs than plain water?
Is washing your body too often bad for the skin
Are there health risks to not washing your hands after urinating
