Hi, Itching from neck to ankle since long time could be due to subcutaneous candidiasis, a topic dermatitis, allergic reactions,urticaria or hives, or some medical disorders like DM,jaundice, uremia etc. As you are already consulted several times to dermatologist but no clear diagnosis yet. You must try antifungal oral medications once with the help of dermatologist with other supportive treatment.Also you can take immunoglobulins with consultation of dermatologist. If still no diagnosis or cure then it would be advisable to consult physician to rule out any medical disorders since you are taking antihypertensive,hypolipidemics with some vitamins. You can go for allergic testing of food and other substances but they are not such reliable.