user1816: At the recent Isle of Mann coverage, the topic of conversation was grandmaster superstitions, during which GM Simon Williams conveyed that Karpov would only wash his hair when he lost a game. Apparently he went over 40 games without a loss during a streak, leaving it up to our imagination on the consequences.
Now I know GM Simon Williams is quite the joker, so I'm inclined to believe that this is just one of his jibes, but is there perhaps any truth to this? I found some references to this with Google, but I'm not sure about how authoritative they are.

user4418: This story has a very long pedigree going back much further than the GingerGM.
The earliest reference I can find on the internet is from a November 1985 report on the Karpov v Kasparov match in People.com's archive - http://people.com/archive/anatoly-karpov-is-straining-in-vain-to-keep-his-world-chess-title-from-gary-kasparov-vol-24-no-20/

Unlike his extroverted rival, Karpov — who has all the appeal of a
  cold fish —ignores the crowd. When he intends to play aggressively, he
  emerges onstage clad in a black suit. In keeping with a chess
  superstition, he hasn’t cut his hair during the current match. Indeed
  he seldom seems to wash it, and he has been losing weight to boot.

Paul Hoffman (https://paulhoffman.wordpress.com/2007/11/19/superstition-in-chess/) says he mentions it in his book "King's Gambit"

In King’s Gambit, I write about superstitions at the board. Players
  who insist in wearing their lucky T-shirt or underwear or keeping
  score with the same special pen. World champion Anatoly Karpov was
  famous for not washing his hair when he was on a winning streak.
  Grandmaster Nigel Short said of Karpov: “Unfortunately, he had long
  tournaments where he never lost a game—the guy got greasy.”

The English Chess forum brought this up in a thread on "Poor Taste" - http://www.ecforum.org.uk/viewtopic.php?t=2045&start=30#p36136 - back in 2010.

1816: <p>At the recent Isle of Mann coverage, the topic of conversation was grandmaster superstitions, during which GM Simon Williams conveyed that Karpov would only wash his hair when he lost a game. Apparently he went over 40 games without a loss during a streak, leaving it up to our imagination on the consequences.</p>

<p>Now I know GM Simon Williams is quite the joker, so I'm inclined to believe that this is just one of his jibes, but is there perhaps any truth to this? I found some references to this with Google, but I'm not sure about how authoritative they are.</p>
 4418: <p>This story has a very long pedigree going back much further than the GingerGM.</p>

<p>The earliest reference I can find on the internet is from a November 1985 report on the Karpov v Kasparov match in People.com's archive - <a href="http://people.com/archive/anatoly-karpov-is-straining-in-vain-to-keep-his-world-chess-title-from-gary-kasparov-vol-24-no-20/" rel="noreferrer">http://people.com/archive/anatoly-karpov-is-straining-in-vain-to-keep-his-world-chess-title-from-gary-kasparov-vol-24-no-20/</a></p>

<blockquote>
  <p>Unlike his extroverted rival, Karpov — who has all the appeal of a
  cold fish —ignores the crowd. When he intends to play aggressively, he
  emerges onstage clad in a black suit. In keeping with a chess
  superstition, he hasn’t cut his hair during the current match. Indeed
  he seldom seems to wash it, and he has been losing weight to boot.</p>
</blockquote>

<p>Paul Hoffman (<a href="https://paulhoffman.wordpress.com/2007/11/19/superstition-in-chess/" rel="noreferrer">https://paulhoffman.wordpress.com/2007/11/19/superstition-in-chess/</a>) says he mentions it in his book "King's Gambit"</p>

<blockquote>
  <p>In King’s Gambit, I write about superstitions at the board. Players
  who insist in wearing their lucky T-shirt or underwear or keeping
  score with the same special pen. World champion Anatoly Karpov was
  famous for not washing his hair when he was on a winning streak.
  Grandmaster Nigel Short said of Karpov: “Unfortunately, he had long
  tournaments where he never lost a game—the guy got greasy.”</p>
</blockquote>

<p>The English Chess forum brought this up in a thread on "Poor Taste" - <a href="http://www.ecforum.org.uk/viewtopic.php?t=2045&amp;start=30#p36136" rel="noreferrer">http://www.ecforum.org.uk/viewtopic.php?t=2045&amp;start=30#p36136</a> - back in 2010.</p>
