I hav a rash on both arms and knees it itches like crazy! had it for a very long time was told cardboard mites but cnt find them i have tried benadryl (diphenhydramine) spray cream and pill and nothing helps!

Hard : Hard to tell without a clinical examination, but perhaps it is psoriasis or eczema? Read more about these conditions (and a classic picture on the arms, legs) and treatment options at the link below. I hope that helps a little!

Eval: This rash would likely need to be examined and more history obtained to be able to provide you with useful input about the diagnosis or possible treatment.