Seborrheic keratosis--or SK's as dermatologists call them--are superficial growths that look like little brown flat warts and normally start to appear in your 40s. They come in all colors: flesh, black, brown, gray, or even white. They usually start small and look like an age spot that is slightly scaly. They can stay small and flat or they can become very thick rough. Sometimes you can even peel them off your skin with your fingernail (or at least you feel like you can get your nail under it and peel it off).
These skin lesions can be the size of a needle point or grow to be the size of a silver dollar and half an inch thick. This is why they are commonly referred to as "barnacles." When you apply sunless tanning cream the SK's light up and turn very dark. This is because they are composed of thickened skin so just like your elbow, knees, and calluses on your feet turn brown with sunless tanning cream, so do the seborrheic keratosis.
Seborrheic keratosis spots are the vain of adult womens' existence. Because they take so many looks and shapes, they are often hard for a patients and regular doctors to diagnose, as they can resemble the appearance of skin cancer. While they are harmless, they are very difficult to treat.
Individual lesions can be cured with just one treatment. Some spots may require several treatments. New lesions will continue to come as you age, so be patient as time goes on. The most realistic goal is to stick with reserving treatment to just the spots that present themselves on your face and chest.
Using Retin-A to your face and chest can help prevent them from forming in the first place. Once they appear, though, they can be treated with laser treatments if they are very thin. When they mature and become thicker, they will need to be treated with liquid nitrogen, chemical peels, or ablative lasers like the Encore CO2 Fractional or Erbium lasers.
The best advice is to see a qualified dermatologist who can make a diagnosis and discuss realistic treatment options with you. Settling for treatment at a spa, with untrained skincare providers, will wind up costing you thousands of dollars in misdiagnoses!