Listerine Lice Treatment: Why It Doesn't Work

The Rundown

First of all, don’t use Listerine as a treatment for lice. Just don’t. It may be an appealing alternative due to its price when compared to the price of lice shampoos and treatments, but that’s because it’s not a lice shampoo.

To be classified as a lice treatment, products must go through extensive testing by the FDA and other regulatory agencies, submitted in clinical trials, and proven to be consistently effective. Listerine has not done that. It is a mouthwash, not a lice shampoo.

The Ingredients

Listerine
Active Ingredients: Alcohol (30%)
Other ingredients: Eucalyptol, Thymol, Menthol, Methyl Salicylate

Suffocation vs. Dehydration

The reason Listerine doesn’t work to eliminate lice is that different chemicals treat lice differently. The active ingredient in Listerine is alcohol, and alcohol-based alternative lice treatments (like Listerine) predominantly rely on suffocation to eliminate lice. This is a good step, but far from an effective, permanent solution.

Head lice in the egg stage have a protective, waxy coating that acts as a waterproofing agent and allows them to continue their evolution into live nits. (While Listerine may loosen some of the eggs, it’s not enough.) The alcohol in Listerine deprives the eggs of oxygen in order to suffocate them; however, it can take 8-24 hours for suffocation to occur. In that time, the lice eggs can lie dormant and the Listerine wears off. As a result, the affected party will need almost constant Listerine treatments over the course of several days to ensure the lice eggs don’t hatch. In addition, any live nits and eggs will still have to be combed out with a special lice comb.

Method

Why, then, do some people swear by Listerine? The secret may be more in the act than in the ingredients. Many articles that identify this particular method as a solution also call for the use of a lice comb and vinegar. It is more likely the act of combing out the lice with a lice comb, combined with the vinegar, that eliminates the lice more than the active ingredients in Listerine themselves.

Remember those breakfast cereal commercials on Saturday mornings for Apple Jacks that said “part of this complete breakfast,” then showed the sugary cereal alongside four apples, three bananas, two eggs, and a grapefruit? You got the feeling the cereal wasn’t really the main contributor to the “complete” part of the meal.

When it comes to lice treatment, Listerine is much the same as Apple Jacks. It may work as “part of the complete breakfast,” but it is not the key ingredient, or even beneficial to the lice treatment diet. In much the same way the fruit and veggies end up doing most of the work to make up the complete breakfast for the sugary cereal, the lice comb bears the bulk of the responsibility for delivering results on behalf of the Listerine.

Do head lice change color?

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?

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 color. 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 color until after they’ve fed.

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

The ‘wisdom’ that human head lice change color depending on the hair color 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 color 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..