To build off of what
lollicup said, before man became domesticated we were wild ( also known as "Natural Man" ). Natural Man had a layer of natural, beneficial bacteria known as "
Flora" which acted ( basically ) as a shield against harmful bacteria. As man became more domesticated it became "normal" to wash the skin more regularly ( understandably so ), and while this made us smell better, and more appealing to others, it did dramatically reduce the amount of natural skin flora that resides on human skin and thus made us more susceptible to external, harmful bacteria.
So, while normal cleaning after coming in contact with harmful bacteria is absolutely beneficial seeing as our natural skin flora is not as effective as it was before, constantly sanitizing yourself, and further inhibiting the development of natural skin flora will only be detrimental to your health.
Case in point, I work in the medical field and am constantly in contact with ill people, blood, extreme temperatures, so on and so forth. I simply wash my hands regularly and I never get sick. I have never received a flu shot and still never get sick, and by never I mean I have only been sick three times in my life.
- Chicken Pox when I was eight.
- An Ear Infection when I was 12.
- An Ear Infection when I was 23.
I haven't been sick since.
So being a germiphobe is really counter-productive.
But ultimately, I know it is a psychological issue, and nothing I could say would encourage you to change your habits.
That Said, Here's What You Can Do.
Get a box of antibacterial wipes and wipe your phone with those. They are alcohol based so they wont cause water damage, but keep them away from the moisture sensors ( Headphone Jack and Dock Connector ) just to be safe.
I hope this helps.