A chemical called methylisothiazolinone (MIT), which is found in shampoo and many other household products, has been shown to be a neurotoxin–that is to say that it kills nerve cells. Nerve cells, when directly exposed to MIT, die. The concentration of MIT needed to kill the neurons is about the same as the amount found in hand cream. Long-term exposure to low concentrations of MIT can interfere with how the neurons communicate with each other.
MIT is a biocide, which means that it is in the products to prevent bacteria from developing. There is controversy about whether the chemical is harmful to humans using the products that contain it. The animal studies involve direct exposure to the neurons—the substance kills cells that it comes into contact with. Industry spokesmen and some scientists point out that the chemical would need to get into the bloodstream to do any damage, and that this is unlikely. Other scientists point out that the chemical has not been tested on humans to see if it can cause neurological damage. The National Institute of Health has a list of products containing MIT, just follow this link: MIT.
