Why is my eye really itchy?

My left eye is really itchy and I try not to rub it but I can't help it. When I rub it, i feel liquid come out. It's clear. It did this yesterday but I put eyedrops in it and it finally went away. When I blow air against the eye it feels good. It's not swollen or red but when I keep rubbing and rubbing it seldom gets a tad pink. Why is it so darn itchy?