Suggest Remedy For Itchy Rashes On Arms, Chest And Legs

Every fall around August and every spring from April to June I get a very itchy rash on my arms, legs, chest, elbows, back of knees and tops of feet. The itch comes and goes but can get so intense that itch until I bleed. It comes in tiny raised red bumps. I have been to the ER for this several times, and they have prescribed me medications for scabies, eczema, psoriasis, creams for contact dermitis etc.. I have had this for 4 years now and nothing helps. It is just starting to act up now and I really would like to find something, anything that can help. Does anyone know what this could be, or things I could use to help?