What Causes Dry Skin On Top Of The Penis Foreskin?

Dear Doctor, I am male age 31 and virgin. I have noticed a dry skin on top of my pennies fore skin. It will visible when i do masturbate or rub. The IMG1.jpg shows you the clear picture of my dry skin. IMG2.jpg is just closer look. Once i shower my privates parts it slightly disappears like shown in IMG3.jpg. Please let me know if you need any other information from me. I'm looking forward your advice in your earliest convenience. thanks in advance. Regards, Sam