Head Lice: Becoming resistant to medications?

Help! My son continues to get head lice despite my best attempts. I've read your previous answer on head lice, and I seem to be following what you suggest. But he still keeps on getting it. Isn't there something else I can do?


Robert Steele

Robert W. Steele, MD, is a board certified pediatrician at St. John's Regional Health Center in Springfield, MO. He graduated from medical... Read more

I have received a number of letters similar to yours. Interestingly, the problem you describe has just recently become a hot topic of discussion among pediatricians and dermatologists. Specifically, are head lice becoming resistant to the medications most commonly used to treat them? The answer is a qualified "Yes."

Most physicians still feel the strategy I outlined in my previous answer on head lice is sufficient for almost all cases. But while many failures to eradicate these pesky bugs had previously been blamed upon incorrect techniques at home, there is now some possible laboratory evidence that head lice may be becoming more resistant. Of course, this is nothing that many parents haven't already suspected. But it wasn't until now that there was additional evidence to suggest our current strategies may not be as successful as in the past.

Therefore, a few extra "tricks" have popped up for parents to try should they be unsuccessful with the normal strategy. However, I must emphasize two things:
• The approach I outlined previously will work for most situations, so considering the following alternatives may be a completely unnecessary time-consuming process for many parents and their children.
• The suggestions below have not been formally studied, so their effectiveness cannot be guaranteed.

Now, on with the suggestions:

• Put petrolatum (Vaseline) over the entire scalp, cover the head with a shower cap, and leave it on all night. This method is supposed to kill both the lice and the nits. The reasoning behind this is that this thick substance essentially suffocates the lice by clogging their respiratory system. Obviously, the biggest problem with this is keeping the petrolatum off the bed sheets and getting it out of the child's hair the next morning.

• Most head lice medications are made up of one percent permethrin. However, there is a five percent permethrin medication available which appears to be safe when used in the same manner as the one percent. Ask your doctor whether she feels this might be a viable option.

• Leave the one percent permethrin on longer. Some have tried leaving it on overnight with a shower cap on. Again, I suggest checking with your own physician before trying this method.

• Ask your doctor about prescribing the antibiotic, Co-trimoxazole. This is probably the least proven method of the bunch. Nonetheless, the reasoning behind this approach is that this antibiotic gets into the lice when they bite; then the antibiotic kills certain bacteria that live in the lice's gut. These bacteria are necessary for the lice to produce certain life sustaining vitamins. Without these vitamins, they die.

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