How To Treat Itchy Rash On Shin?

I have a rash on my shin, incredibly itchy i can't stop scratching until it hurts so much. Salt water helps, I have seen a local doctor who has taken a blood test. told me it was eczema and i used a cream but it still comes back. Clothing even cotton irritates. it is patchy and slightly raised. I have been taking antihistamine tablets to help with this. What could it possibly be?