Lice are hard to see, and sometimes seeing is in the eye of the beholder. This means parents that don’t want to see head lice on their child’s head often take a quick glance and assume everything is ok. On the other hand, parents that have dealt with head lice before and that are very proactive tend to see lice even if they are not there.
Researchers at the Laboratory of Public Health Entomology at the Harvard School of Public Health (HSPH) have found “that health care workers, parents, and school officials often misdiagnose and inappropriately medicate head lice infestations.”
So, what do lice look like? Well, they are small—about the size of a sesame seed. Also, they tend to stay close to the scalp (about a quarter of an inch away) where they can stay warm and feed regularly. It can be hard to get a good look at them with the naked eye, especially on people with very long hair.
Lice are brownish and off-white in color and have six claws highly evolved for clutching human hair (they can’t live on any other species). A magnifying glass and/or a flashlight or lamp is often needed to clearly see them. As the Harvard study found, many people mistake dandruff, dry skin, scabs, or knotted hair with lice. With a magnifying glass, good light, and a fine toothed-comb, live lice can be removed.
Eggs, or nits, are even more difficult to detect. They are glued to hair shafts and blend in with most hair colors. Nits are harder to remove, even with a lice comb. Usually, they must be manually removed, nit-by-nit—a process that is highly prone to human error and that often results in prolonged battles with the bugs. A missed nit or two will then hatch, and the battle starts over.
Another cause of prolonged lice battles is the fact that the active ingredients in most over-the-counter products have lost much of their effectiveness. Multiple studies have shown that most lice in the U.S. and elsewhere have become resistant to pyrethroids, the class of chemicals (or poison, depending on who you ask) used in anti-lice products.