Hi, I can understand the concern for itching on arms, lower legs and thighs and sores on breast. YOu have not mentioned your age, occupation and any relevant history which could have guided us to the nearest possibility. I advise you to not pinch or pop the area otherwise these areas are very prone for getting secondary infection. You can apply an steroid cream such as cortisone cream. You should preferably meet a dermatologist who can examine you physically and provide you the best treatment. For time being period you can apply antibiotic cream such as fucidin or mupirocin and take antihistamine tablet such as loratadine or cetrizine. Do not try to even touch or pinch the area as can cause more aggravation of the problem. Take care.