What Causes Severe Itching At The Urethral Opening?

I have been suffering from itchy (slightly painfull when pressed ) urethral opening on my glans since the last two years. the level of pain /itch is bearable and has variations in intensity with time. No discharge has ever been noticed and there is no other visible signs than a slight reddish rash near the urethral opening on the glans. the pain and itching sensation is a bit deep under say by about one centimeter from the tip of the glans. Kindly let me know what treatment should i follow..Thanks a lot for your timely help.