No, lice won't go away on their own. Here's what treatment works.
If you've ever experienced head lice, you know how uncomfortable they can be. These tiny, parasitic insects are also unsettling and can be tough to get rid of. "An infestation might feel like tickling on the scalp and can cause difficulty sleeping as lice are most active in the dark," says Dr. Sara Ritchie, a pediatrician and clinical assistant professor in the department of pediatrics at the Medical University of South Carolina.
Complicating matters, many people don't know they have lice until 4-6 weeks after infestation - usually because that's when skin becomes irritated by lice bites and lice saliva and begins to create an itching sensation. As tempting as scratching that itch may be, doing so "can sometimes cause a secondary bacterial infection of the skin," cautions Ritchie.
Do lice go away on their own?
While head lice infestations can be frustrating and inconvenient, it's important to note that they don't resolve on their own and require treatment for elimination. "Without intervention, lice can reproduce and persist," says Dr. Jason Nagata, a pediatrician at UCSF Benioff Children’s Hospital in San Francisco.
One reason for this is that lice feed on human blood and don't survive more than a day or two once they fall off the scalp. What's more, the eggs of head lice - called nits - cannot hatch and usually die within a week of being removed from the ideal heat and humidity conditions found close to the human scalp, per the U.S. Centers for Disease Control and Prevention (CDC). Because of this, unless they are removed, lice will remain on the scalp environment, near their food source, and don't have any reason to leave.
How to get rid of lice
While suggestions exist online of getting rid of lice by suffocating them with occlusive agents such as mayonnaise or oils, these have no effect on nits and have been met with only minimal success against live lice, says Ritchie. These techniques aren't recommended by any official health agency either.
Instead, "over-the-counter medicated shampoos or prescription treatments with permethrin or pyrethrin are best to eliminate head lice," says Nagata. Permethrin lotion goes by the brand name Nix, and it's an FDA-approved treatment for eliminating head lice. While it's considered safe and effective to use on adults or children 2 months and older, this lotion kills only live lice and not unhatched eggs, per the CDC, so a second treatment is often necessary 9 days after the first one to ensure that any newly hatched lice are killed before they can produce new eggs.
Pyrethrin is an active ingredient in lice shampoos and drug brands like A–200, Pronto, R&C, Rid, and Triple X. This naturally-occurring ingredient is extracted from the chrysanthemum flower and gets absorbed by lice and destroys them by acting on their nervous system, notes Mayo Clinic. Similar to permethrin lotion, pyrethrins don't kill unhatched eggs, so a second treatment is usually recommended 9 days after the first.
Before applying either form of treatment, it can be helpful to comb over one's scalp. "Lice and their eggs cling to hair strands and can be challenging to remove without the use of a fine-toothed comb to first loosen them," explains Nagata.
Getting rid of lice can also be easier to do if you discover them before they've proliferated too much. "Head lice are best diagnosed by finding a live nymph or louse on the scalp," says Ritchie. Each is about 2-3mm long, which is about the size of a sesame seed, "and they are most often discovered behind the ears or near the back of the neck."
How to prevent lice from returning?
As you effectively deal with lice and their eggs on the scalp of any infected people in the home, it's important to also address bedding or clothing materials that lice may have come in contact with to be sure they won't re-infest anyone in the home later on.
To do this, the CDC recommends machine washing clothing, bed linens, and other items that an infested person has worn or used within 2 days before starting treatment. This can be effectively done by using the hot water option on the washing machine and by drying the load on the highest heat drying cycle. "If items cannot be laundered, seal them in a plastic bag for 2 weeks," suggests Ritchie. Such items may include combs, pillows, stuffed animals or clothing items not suitable for washing machines.
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It's also advisable to avoid laying on couches or carpeted surfaces that have recently been in contact with an infested person. This is only needed for a few days - to ensure any remaining lice on those surfaces naturally die off. "But there is no need to use fumigant sprays or fogs in the home," cautions Ritchie. "Neither are necessary and may be toxic if inhaled or absorbed on your skin."
