Exma thing on my foot my whole life please help?

this started since I can remember, its a foot ema thing, starting on my ankle. in the shower, or when it gets wet, it hurts, and goes red. but its white when its dry. when a cream is on it, it goes red, for one hour-a day. depending on if it stings. its looks SIMILAR to this;http://www.healthhype.com/venous-stasis-in-the-legs-symptoms-with-eczema-ulcer-pictures.html the first picture on it, but without the the red bits. I've gone to the docters ever since I was four. they tell me the same thing "I don't know exactly what this is but try this cream" only one of those made a small effect. its itchy, when I scratch it to much it bleeds, but I dont feel it. it only stings when its in the shower. now please? I've had this since like four and im nearlly thirteen now. I don't mind about it to be honest. idc if it stays there, its what people say about it that upsets me. its only on my right foot, and like half a cm long on my left. can you tell me what this is exactly, I dont think its what it said on the page btw. its NEVER purple, only white & sometimes red. HELP!?!?