Sodium hydroxide is used in some relaxers to straighten hair. Guanidinium hydroxide is the active ingredient in some non-lye hair relaxers. The scalp can suffer severe chemical burns if over exposed to lye or no-lye relaxers. Bleach oven and drain/pipe cleaners, hair relaxers, and lye are examples of alkaline products. During the discussion, Rock noted that many women used hair relaxers to straighten their hair. He visits scientific laboratories to learn the science behind chemical relaxers that straighten hair. Thio relaxers break the disulfide bonds in hair, similar to the permanent waving process. Mild cases are usually treated by the administration of analgesia and muscle relaxers. Sodium hydroxide relaxers are still available, but they are used mostly by professionals. On September 13, 2010, WWE updated their list of banned substances to include muscle relaxers. Chemical relaxers increased in demand throughout the 1800s and 1900s. Many African-American women gave up relaxers to go back to their natural roots. Brands have greatly lowered their production of relaxers and instead now produce more natural-friendly products. Sales of relaxers took a great fall among African-American women from 2010 to 2015. Rock pleaded with parents to stop exposing their young daughters to relaxers.