Ok I have had this sub-type as well. There are generally two ways this behaviour starts to manifest itself.
First, it can start from a feeling of not being able to complete a task the "correct" way. So you would repeat the action until it feels right. This can happen with many more things than just hand washing too.
But if it happens to occur during washing your hands or even your body in the shower, than you're more than likely going to get in the habit of washing til it feels ok to stop.
Second way is from germ phobias, which are kind of like a sub-type of their own.
Either way it begins, it will devastate your hand skin and usually if you have germ phobias, you'll start washing up past your hands onto your arms as well. I did. I had raw hands and the inside of my elbows were pretty raw too. I had lacerations all over my hands and my skin would peel in tiny strips.Gross right? And it was painful too. But I couldn't stop.
It's funny because along the lines of washing because of germ phobias, you're trying to wash off germs so they won't be on you or enter your body, but by making your skin raw and lacerated by compulsively washing, that is actually exactly what you're doing, letting the germs in. So you're defeating the purpose really. It's an awful mess to be in. But it can be stopped.
How to stop it?
For washing until it feels right:
First thing you need to try and come to grips with is you're never going to be able to do anything perfectly. No one is able to do that.
By thinking you can you're already setting yourself up for failure. You need to try best you can to accept that it may not always feel right when you do something. But that is just how things are sometimes, and rewashing your hands is not going to make it better. What will make it better is to walk away and know that you rewashing your hands will not prevent something bad from happening to someone or something somewhere else.
You know when it's necessary to wash your hands to prevent disease spreading to someone, that would be an exception as far as "hurting" someone..even then our bodies are so strong. If you have basic hygiene down, you're good.
Feeling as if you can prevent something from happening by washing your hands over and over til you feel it's ok or feels right actually makes yourself believe you have the power to control unforeseen occurrences. None of us have that ability as humans. That is part of magical thinking, another sub-type of OCD. To get into the habit of believing you can control things like that is a ridiculously heavy burden to bear and it is not logical. Which I know logical thinking isn't really a strong suit when OCD flares up. But, with practice you can start incorporating this knowledge into these situations and be able to walk away. You may feel upset and panicky still for awhile after you walk away, but nothing will happen. You sometimes have to sit with the uncomfortable feeling for awhile. Sitting with the uncomfortable feeling is a form of cognitive behavioral therapy. Over time the uncomfortable part will fade more and more each time you walk away from a compulsive situation.
For germ phobia washing:
I suffered from this for at least 2 years non stop. And then struggled with it at other periods of time for awhile too, but not as severe. I had fear of blood, and especially of hepatitis, and then of course germs, thinking every little thing was going to kill my family and I, if it should happen to be on us or on something we ate. It's funny because I am such an outdoors person and love nature, so this thinking was so out of character for me. It destroyed me.
The fear of germs though from an irrational glitching brain, is VERY real and very intense. It's like everything you've ever known gets wiped out of your mind and just replaced by fears. Or worse yet, you know what you're doing is irrational, yet you watch yourself freak out knowing it's ridiculous and you can't stop yourself.
I would say first things first, DO NOT google diseases. DO NOT DO IT. That will be your downfall. It won't help you, it'll just feed the fear, because there are a lot of bad germs and diseases out there and you're going to be reading info on what they can do to your body. These articles are usually written in a worse case scenario kind of way, so you're not going to find relief there. Best thing to do is remember how wonderfully our bodies are made and you and your family have survived thus far, and you're living in the same world with the same germs that you were living in before you developed this phobia.
In fact when you're a baby it is actually better for your immune system to put all kinds of germy things in your mouth as it builds your immune system and you grow into a stronger person, as opposed to a baby whose mother (who maybe has germ phobias) keeps everything that has not been thoroughly sterilized away from her baby. That baby's immune system will not strengthen properly.
Just try to remember if you don't already have a compromised immune system, it takes a lot to kill the human body. It is well equipped to fight germs and infection. Another fact too, is we have good bacteria on our bodies that fight off the worse bacteria should we come into contact with it. So if we're frantically washing ourselves all the time in fear of bad germs, we're washing off the good germs in the process, setting ourselves up for a worse situation. Again defeating the purpose.
It is going to be very hard to break this cycle. As much as you can stand it, resist washing after every little thing you touch. I went from basically washing every time I touched something, to being able to eat something that slipped to the ground for a second. That is normal. I have not gotten deathly ill, nothing bad has happened. Everything is fine. The fear is just that, a fear, it's a delusion in your mind. And you will succeed if you just keep making yourself wait in longer intervals after every time you do wash(and I'm not talking about washing your hands when it's necessary, like after the bathroom).
You will still have times where you want to wash excessively after you've overcome the majority of the problem. Stay strong, it will pass and you'll be fine.
Check out the dedicated page to this subject here: Washing Behaviours