Shampoo and Brain Cells

When Dr. Elias Aizenman declared that a common shampoo and ingredient might harm developing babies. brains, it triggered a flurry of news reports, many of them with enough information to alarm people, but not enough to help them decide what to do. He made his controversial statement on December 5, 2004 at the annual meeting of the American Society of Cell Biology. An ingredient called methyisothiazolinone (or MIT) is added in small concentrations to some shampoos and other products as a preservative.

Its job is to kill bacteria and fungus that might grow in the product. Dr. Aizenman and his colleagues at the University of Pittsburgh School of Medicine have previously shown that high concentrations of the chemical, applied to rat brain cells will kill many of them within 10 minutes. The new findings demonstrated that exposure to small amounts over a long period of time could stop unborn baby rats’ brain cells from developing normally. The cosmetic industry was quick to offer reassurance that the preservative would not have direct contact with human brain cells.

What’s the take home message? Do we know enough to say that shampoos containing MIT dangerous to humans? No. Do we know enough to be sure they are safe in all circumstances? Again, no. One of the most important lessons from this story is that we need more information on chemicals that become a common part of consumers. lives, and I applaud Dr. Aizenman for helping us with this ingredient. In the meantime, it makes sense to me for pregnant women to avoid occupational exposure to this chemical where possible (whether in shampoo manufacturing, or any other manufacturing plant). And I might consider using a different shampoo during pregnancy (and perhaps for the elderly).

Thankfully, the National Library of Medicine provides an online Household Products Database where you can look up a chemical such as MIT and find a list of consumer products containing the ingredient. If you do, you will find that a number of popular brands contain it, but that many do not. You will also find quick links to the latest toxicity and medical studies concerning the ingredient, so you can see for yourself what we know. Learning about the Household Products Database may be the most important benefit of this story, giving people tools to learn about the new chemicals that have come to surround our lives in the last generation.

Published on: December 08, 2004
About the Author
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Dr. Greene is a practicing physician, author, national and international TEDx speaker, and global health advocate. He is a graduate of Princeton University and University of California San Francisco.
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