Skin can tingle for many reasons and to get a definitive answer for why yours is tingly, you should really seek medical advice. In the meantime, here are some thoughts on some possible causes:
You're in love!
Some people, when they're close to someone they love, have butterflies in the stomaches. Others get tingly skin. This sort of tingling can be felt anywhere on the body.
You have a cold sore coming
The first sign that you're about to get a cold sore is often a tingle. That is, a singular tingle felt on and off.
Cold sores only occur on certain parts of he body though - where are you getting this tingling sensation?
You have pins and needles
If you've ever sat on your legs for too long or slept on your arm, you may have experienced pins and needles. This feeling is your nerves stretching back into place when pressure has been lifted off them. It feels pretty horrible.
You have been taking medication or illegal drugs
Tingling is a side effect of many different drugs - both prescribed and illicit.