There are real risks in using certain chemicals and then going out into the sun, because these chemicals actually increase the sensitivity or your skin to sunlight, which of course leads to sun burning, sun damage, and ultimately, possible skin cancer. The chemicals in coal tar pitch, sold as a soap, as well as certain printing chemicals that are used in photosensitive printing processes and certain petroleum products that have compound polycyclic aromatic hydrocarbons in them can affect the skin by making it more susceptible to burning.
