This seems to be a very common issue with middle-aged to older people. These spots usually come on during middle age and worsen or increase with age. The docs have no clue what it's from and there really is no known "cure" though some people have had success with eggplant and apple cider vinegar applied to the spots.
I started getting these in my 30s and they are increasing and growing in size. My mother has these all over her back and a friend of mine, in her 50's, has them all over her back too. I don't know why they are concentrated so much on the trunk of the body. My guess is, the body is throwing off toxins from the organs (especially liver) in that area and they can't handle the toxins anymore so they come through the skin.
Would the sprays help clear these up along with liver cleansing and mucuslous diet?