My friends' feet make me lose control

I don't care who it is if you leave me alone with my female friends shoes I sniff, stroke, and blow in seconds. The different scents. The taste. Socks and shoes. It feels harmless because I'm in a committed relationship and have no intention of making any weird personal advances or anything. I respect and care for them. But in those moments I lose control. Return them back to where they belong.

Can anyone relate? Where does this stem from? I know its wrong on a level. But! It also feels about as harmlessly wrong as a wrong thing can.