http://www.ncbi.nlm.nih.gov/pubmed/12420937

The more severely the water is treated and disinfected the less likely there are to be the bacteria I am working with in it. Distilled water won’t, highly purified water won’t. Autoclaved water won’t. They are more resistant to chlorine than are coliforms and are not a target organisms so there is usually no monitoring of them.

When people don’t believe a particular explanation for an observed phenomenon, they are quite likely to deny the observation, not just the explanation. Non-scientific fringe dwellers are likely to do this in obvious ways, which are easy (for us) to discount. But those engaged as scientists or science writers are likely to do it in more subtle ways. This probably contributes to the bias we see in medical science.

daedalus2u: I admit to not understanding your line of research. But if it’s any help — no, our water here is not groundwater. Dams fed from natural catchments; plus occasional direct rainwater. I have no theory as why washing only with water works for me (and not for others); I only have the observation that it does.

I have to wash my hair every day with dandruff shampoo or i’d be flaking all over everything, I also try to keep my hair short so it’s easier to control, no harmful effects from this that i can see…;.)

My bad. Particularly as I was critiquing logic errors.

(Retires with red ears)

I was, however, teasing blog-bud daedalus2u, who probably recognized my comment for the good-natured ribbing that it was intended to be.

While attempting to discern what was more specifically responsible for my kidney, respiratory and skin problems I eventually had a hair sample taken for the cadmium exposure, in addition to blood and urine sampling. While reading up on the purposes of the testing I discovered that cadmium is also found in many medicated shampoos that are touted for psoriasis. What gives, heavy metals for flake control?

As for the smartest actor in the room, I’m sure that she washes her priceless locks in nothing but Venusian ice melt since the oxidizer used to sanitize the plebeian water supply is derived from the chemicals used to gas troops in the trenches of WW I.

O.T. but why do people persist in listening to actors as if they were some sort of academic font and authority. Most of them seem lucky to have escaped high school. Next thing ya know they’ll all start thinkin’ that politicians magically become intelligent the day that they are elected.

My absolute favorites though are the celebs that shill the wrinkle spackle and fat acids that melt pounds while you eat chocolate or sleep. My significant other smokes and thinks it perfectly sensible to buy buckets of animal fat to schmeer over her prematurely desiccating countenance rather than quit inhaling toxic fumes.

I wash it with shampoo every couple of months, or if I’m sick.

Really, it works. Kahn, perkysceptic etc: your individual belief that it can’t work does not mean it doesn’t.

OTOH, I live in a place with clean air. When I visit a city with dirty air, I do need to wash my hair with shampoo to keep it clean. Then I have to put up with increased dandruff, messy hair, aggravated psoriasis etc.

Scepticism is good; but under the guise of scepticism, many people who are trying to defend science end up looking silly when they expose their own irrational beliefs about science.

The number of bacteria that constitute an “infectious dose” depends on other bacteria that are present. To become “infectious”, the bacteria must be present in sufficient quantity for quorum sensing to activate virulence factors. Many commensal bacteria inhibit quorum sensing via a variety of mechanisms. My favorite mechanism is via production of NO/NOx which specifically inhibits biofilm formation for Pseudomonas and Staphylococcus (and many other bacteria).

I thought that at SBM we had moved beyond the miasmatic theory of disease .

I don’t shampoo my hair unless it is dirty enough to really need it too. Once you understand the protective effects mediated through the hygiene hypothesis, what constitutes being “really dirty” changes a lot.

Remind me not to look you up if I’m ever in your neck of the woods. Or at least to wear a respirator.

I do remember that maybe a decade ago, an email got circulated about the TERRIBLE DANGERZ of using any shampoo with the KNOWN CARCINOGEN and BRANE DAMAGEING chemical, sodium laureth sulfate!!! OH the horror!!! This being my woo days still, I ran to the store and searched high and low for a shampoo without sodium laureth sulfate in it!!!

Um. They all have sodium laureth sulfate.

Clear example of an internet prank, and I fell for it gorgeously.

To the guys reading this you might not understand unless you’ve ever grown your hair out but long hair is high maintenance. That sort of thing leads to a lot of “hair woo” which is of course a subset of “beauty woo”.