Coal tar is no longer legal in cosmetics. It was banned in 2005, in the process destroying two really well known brands: Vosene and Wright’s Coal Tar soap. There was evidence that coal tar could cause cancer. This was based on various bits of information, but most convincingly by an increased incidence in cancer amongst people who worked with it. Speaking as someone who has worked with it myself, I think this is a good enough reason to ban it. It is best to be safe, even if it was never shown that it did any harm to people who actually used the products containing it. In fact you can still buy coal tar shampoos, but only ones that are registered as pharmaceuticals.
Coal tar is a byproduct of the coal industry. You get it when you turn coal into coke or natural gas. It is a remarkably unpleasant substance to handle. It has a pungent smell that persists in the nose for ages. It is black and tarry and sticks to most surfaces with which it comes into contact. It is hard to remove and usually leaves a stain behind once you have.
Despite this, there was a time when coal tar was at the cutting edge of organic chemistry. Many organic molecules were first identified in coal tar. In the early years of the industrial revolution coal tar was the only practical source for a lot of chemicals. Even so, we still probably haven’t found out absolutely everything that is in it even today. We haven’t yet worked out exactly why it is carcinogenic. It has also found some positive therapeutic benefits as well, which we equally have never got to the bottom of.
Coal tar is an effective treatment for psoriasis so using it in a shampoo is a great way to treat psoriasis. It doesn’t work for everyone – I have a feeling that we often see the same symptoms in skin diseases arising from very different causes. The three big brands in this area are T-Gel, Polytar and Alphysol. It seems that all three work fairly well, but people seem to find one or other of them works particularly well. I don’t know if that is because people get used to a particular one or if the three different formulations have different effects.
They are quite different, so if you suffer from scalp psoriasis you really need to try all three to find the one that suits you best.
Alphysol is the one with the most actual coal tar and so might be expected to work the best. It certainly has its fans. Polytar has a much lower coal tar content and includes some other plant derived oils. T-Gel has the lowest tar content and the tar is treated to remove the colour and the smell. This makes it the most cosmetically appealing. In fact you could use it as a normal shampoo and not really be bothered by the tar. You would only use the other two if you had a problem because they tend to make your hair smell like you have just puffed your way through a couple of packets of particularly virulent unfiltered cigarettes.
The risks of cancer from these products can’t be completely ruled out, but given how long they have been used it seems very unlikely that evidence will come to light now that users are risking any more than an unpleasant odour. The benefits from improved scalp condition on the other hand are very real. But I can’t believe that this agent is the last word in the treatment of scalp psoriasis. As we learn more about genomics I think we’ll learn why people have such different reactions to therapies, which will be interesting. We should also be able to treat it more effectively, which will be great.
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There is a wealth of information about psoriasis in general including scalp psoriasis avialable from the UK’s National Psoriasis Association
I don’t have any direct personal experience of it, but here is the link to the American version.