Hyper-stimulation is a frequent side effect of the use of any stimulant. Persons who abuse drugs such as methamphetamine and crack cocaine frequently scratch themselves for several reasons. Paranoia is common. Consistent abuse often contributes to malnutrition, lack of sleep, poor hygiene. The skin becomes less supple and dehydrated. Minor cuts and abrasions don't heal as fast and become more prone to infection. The stimulant drugs irritate the nerves in the skin as well. I have never heard of someone scrubbing their skin with bleach but I have seen methamphetamine abusers, especially women, compulsively scrub their skin until it is raw while they are cleaning themselves. Profuse itching and scratching is also often seen with opiate abuse.