Methylchloroisothiazolinone

Of course, I have no idea what it does. All of my chemistry or bio major friends have no idea either. Of course, we all cut a lot of classes together to smoke up, so that's not really saying much.

A web search today reveals surprisingly little, except that it still appears in the ingredients lists of a variety of cosmetics. Rexal identifies it as an "antimicrobial agent with broad-spectrum activity." SPA20, taking a slightly bigger-picture approach, says: "A preservative used in shampoos that was taken from the industry to replace formaldehyde." Sic. Perhaps this is trying to tell us how far the cosmetics industry has come.

I noticed that after a while it disappeared from the list on my shampoo.

This might be explained by references to it in a paper by a toxicologist at the University of Texas-Houston School of Public Health entitled Cancer and Cosmetics. Doh.

Okay, so most of this was stolen from the web - but it does seem to be remarkably similar (chemically) to anilinethiazolinones(ATZ). These are formed by the Edmann degradation reaction to sequence proteins. Which would mean that a methylchloro-TZ is just the MeCl derivative of one of these compounds (a hetrocyclic pentameric ring).

Presumably, 'preservative' means antimicrobial/antifungal agent. So it's basically an antibiotic.

If you have a hair care product that contains this you might want to stop using it *right now*.

I recently attended a conference of neuroscience researchers at the University of Pittsburgh, one of whom has found that this compound (as well as its relative methylisothiazolinone, or MIT,) is a mammalian neurotoxin. When these results are properly published I will post the reference, and perhaps even some excerpts if I feel like violating copyright law.

There are many hair care products that do not use either of these compounds, though you may find that so-called "natural" or "botanical" products are not often MIT/MCI free.

(Of course, if you really believe that putting plant extracts in one's hair helps it get clean, then you might as well keep using your spontaneous-orgasm-in-a-bottle-with-papaya folicle treatment; I don't think the neurotoxicity will bother you much . . .)