I have a pimple-like, non-itchy, rash on my back. not red or visible from far. spread to whole back over 2 weeks. no new products or other symptoms. ?

Rashes need exam for: diagnosis. Since it is not itchy or red and located just on the back, it does not sound like allergic reaction or viral exanthema. A common cause of papules on the back is miliaria, or heat rash, which is caused by blocked sweat pores. Alternatively, dry skin can cause blockage of the hair follicle and cause small papules or keratosis pilaris. This is benign, and is commonly seen on upper arms