My legs often itching and can't stop it, there is nothing image no erythema no bubbles no wound .what can cause itching ?

Neuropathy: You may have a neuropathy. I would consult with a neurologist.

Many possibilities: There are many things that could cause the skin to itch. Several types of inflammatory conditions of the skin, allergic reactions, and sometimes bacterial, viral or fungal infections can cause rashes on the skin. Insect bites can also be the cause of a rash on the skin. Have it evaluated by a professional and get the appropriate treatment.