Tuesday, 12 October 2010

Black lice? Do head lice change colour?

According to the research of R. Hoeppli, ancient Chinese medicine used lice to cure “high fever and severe headaches as if the skull is cracking.” A paste made from 300 – 500 black lice, spread on the head, was said to do the trick. I must admit, I’d rather have 500 pureed lice on my head than 500 live ones, but the question this raised for me was where one would find black lice. Is there such a thing?

[caption id="attachment_135" align="alignleft" width="300" caption="CDC/James Gathany"][/caption]

Head lice that I’ve seen have ranged from pale ivory through a golden – sometimes reddish – brown; magnified, they are transparent. Lice that have fed have a black mass inside – presumably blood in the process of being digested – but are not, themselves, black. There is a colour range, to be sure. But black? A literature search turned up some interesting things:

  • Head lice may have a natural way of blending in without actually changing colour. Ibarra and Hall wrote: “Eggs and lice are well camouflaged, reflecting the colour of their surroundings.”

  • Newly hatched lice that have not fed are transparent (Meinking) and do not have colour until after they’ve fed.

  • Colour that matches the background has been shown to have evolved in other species of lice (Bush et al.). This, however, refers to colour change over generations, not within the life span of a single organism.

The ‘wisdom’ that human head lice change colour depending on the hair colour of the host is oft repeated on websites and in non-academic publications. Published scientific information to back it up, however, appears nonexistent. Similarly, parasitology texts and laboratory identification references do not mention it.

I remain highly skeptical that our head lice can change colour within one generation, or that black head lice actually exist. I conclude that the Chinese remedy called for human head lice that had fed and had blood in their guts.

Bush, Sarah E et al. 2010 “Evolution of Cryptic Coloration in Ectoparasites.” The American Naturalist 176: 4

Hoeppli, R.  1959. Parasites and Parasitic Infections in Early Medicine and Science. Singapore: University of Malaya Press, pg 181.

Ibarra, J., and DM Hall. 1996 “Head Lice in Schoolchildren.” Archives of Disease in Childhood, 75.

Meinking, Terri. 2004 “Clinical Update on Resistance and Treatment of Pediculosis Capitis.” American Journal of Managed Care. 10:9, Sup.


  1. With all the spam crammed on the internet it's hard to come by a useful site anymore thanks for the info.

  2. I have been bothered by bed bug bites this past summer. It was one of the most aweful experiences I've ever had. Those bed bug bites have been difficult to watch as well as given I couldn't describle how I got those bites precisely, my family doctor can't do amuch about it. I ended up knowing they were bed bug bites and have learned my lessons.

  3. Actually, I work as a professional nitpicker, and lice change color as they reach adulthood. Fully mature, egg laying adult lice are pitch black from top to bottom. You don't see them very often as they are nearing the end of their life cycle and die, fall off, usually being mistaken for other more common bugs on the floor.

  4. That's interesting and helpful. Thanks so much for commenting! I wonder how much of the dark colour can be attributed to ingested blood.

    Just for fun, I did another quick internet search and still could not find an authoritative site that described black lice. If you could get a good picture, I would love to revisit this topic.

    I didn't know there was such a thing as a professional nitpicker. Given the risks of insecticide exposure and the problems with resistance, I'm pleased to learn that you're out there.

    Thanks again for sharing your expertise.

  5. I will most definitely take a photo at work as soon as I see one again. There really aren't many reliable sites as far as head lice are concerned, and research on the subject is scarce, so we do our own. I don't know if the amount of blood in the parasites' system colors them, but I can tell you that when they are feeding, they're bright red. As the blood digests, it gets darker throughout the louse's midsection. By the time it is excreted, it is a tiny black dot that when you add water, turns red on a pale surface.
    Thank you for making this page, as there are many myths about head lice that need to be cleared up; the most harmful myth being that pesticides kill lice and their nits (eggs)! Please let people know that far too many of our clients come in 2-3 days after using pesticides with all four life stages of lice on them! The ONLY way to get rid of lice that is guaranteed is to manually remove them.