I have this rash on my both of my arms, its on the bicep area. The same thing is on my legs around the ankle area. What can cause this rash a virus or a bacteria?.... I ve seen the doctor, he prescribed erythromycin stearate , I have taken the antibiotic for 6 days now. Still, see no improvement. What do you think it is? (Red, bumpy, very itchy round patches. pimple size to a diameter of a quarter) Thanks