I’ve written here a couple of times before about variants of the “hygiene hypothesis” — the idea that our environments, which are extraordinarily clean by evolutionary standards, are keeping some children’s immune systems from developing normally, because they are not exposed to the range of microorganisms that the immune system needs to “see” in order to calibrate itself. There has also been concern that over-use of anti-microbial agents to remove bacteria from the environment may contribute to antibiotic resistance.
The New Scientist today has a short article relating concerns about another widely used compound, triclosan, which is used as an anti-bacterial and anti-fungal agent in soaps, toothpaste, deodorant, mouthwash, other cosmetic products, and household cleaning supplies. There is some evidence that its use in toothpaste may help in the prevention of gingivitis, but there is no clear health case for its widespread use.
Although there have been, in the past, some concerns expressed about the possibility that triclosan might contribute to anti-biotic resistance, more recent concern has focused on its possible role as an endocrine hormone disruptor.
Over the next year, the FDA will look at evidence that triclosan might affect the development of the nervous system, in which thyroid hormones play a key role, or the reproductive system.
Animal studies suggest that triclosan can lower the levels of thyroid hormone, and boost the effect of estrogen and testosterone.
It seems that we have, for some time now, been engaged in a large and uncontrolled experiment that will determine the effect this and many other chemical substances will have on human health. We should not, perhaps, be entirely surprised if we do not like the answer.