Resistant Lice on the Head Treatments and Remedies

The emergence of resistant head lice has become a public health concern in recent years but the possibility of this drug-resistance has been known for decades. Head lice infestation is estimated to affect as many as 12 million children in the age group of 3 to 11 years in the United States. The growing resistance has far reaching consequences for a significant portion of the American population, but the resistance does not mean that eradication is now impossible.

Common Questions About Resistant Lice

There are three types of lice that causes an infestation of the head, body or pubic region. Pediculus humanus capitis is the louse responsible for head lice infestation, which is also known as pediculosis capitis. Pediculus humanus corporis causes an lice infestation of the body and is known as pediculosis corporis. Phthiriasis pubis is the louse responsible for infestations in the pubic region, which is also known as pediculosis pubis.

From all of these lice infestations, head lice is by the more common problem.

What are resistant lice?

Resistant lice is a term referring to lice, specifically head lice, that are no longer destroyed by common lice medication. The drug that lice have become resistant to is known as permethrin, a synthetic version of pyrethrin. However, resistance does not mean that these drugs are entirely ineffective. It is also important to understand that not every case of head lice infestation involves resistant lice although it is becoming more common.

Why does resistance occur?

As with other organisms that become resistant to drugs that kill it, genetic mutations in lice have now made it resistant to permethrin. This is similar to the genetic changes in bacteria that has led to drug-resistant bacteria. The reason why drug resistance occurs is because of overuse and at times incorrect use of these drugs. Over time organisms are able to adapt and therefore become drug-resistance.

What are the dangers of resistant lice?

Fortunately head lice infestation is not a serious condition. It can in some cases lead to complications where scratching causes breaks in the skin and then the area may become infected by bacteria. Some of these bacterial infections of the skin can be serious. The main problem with resistant lice is that it can rapidly spread to more people and this may occur to a greater extent when lice are resistant.

How common is lice resistance?

Resistant lice is being seen more often these days. Although it was reported as early as 1995 outside of the United States, it was only seen in the USA by the 2000’s. In recent years it has become more common and in 2015 there were media reports that resistant lice has been found in half of U.S. states. Some studies found that resistant lice accounted for the majority of head lice cases assessed.

Treatment for Lice Resistance

Although lice resistance is a growing problem, there are still treatment options available for eradicating head lice. It is important to note that the resistance is to OTC (over-the-counter) drugs but there are still prescription medication for treating head lice. This includes:

  • Benzoyl alcohol
  • Malathion
  • Ivermectin
  • Spinosad

Lindane is another drug that can be used for treating a lice infestation. It is available as a cream, lotion or shampoo. However, it can lead to serious side effects like seizures and is not commonly used for eradicating lice. Lindane should not be used in children.

Benzoyl Alcohol

Benzoyl alcohol affects the respiratory apparatus of the lice thereby leading to suffocation. It is used as a lotion with 5% benzoyl alcohol and has been approved for use from the age of 6 months.


Malathion blocks the enzyme cholinesterase in insects but is broken down by the human body and is therefore not toxic to humans. It is prescribed as a 0.5% lotion and is approved for use in children from the age of 6 years.


Ivermectin targets the nerve and muscle cells of lice and can lead to death of the lice. It is available in a topical and oral form. The topical form is available as a 0.5% lotion and can be used from the age of 6 months. The oral form is available as a 6mg pill.


Spinosad affects the nerve cells of the lice, causing paralysis and death. It is available as a 0.9% topical suspension and can kill both nits and adult lice. Spinosad can be used from the age of 4 years upwards.


The medication mentioned above can only be acquired in the United States with a prescription from a doctor. Never source these drugs without consulting first with a medical practitioner. Some of this medication can be highly toxic and needs to only be used on certain age groups. Incorrect use can lead to serious side effects, especially in children.

Remedies for Resistant Lice

The following non-drug measures may be used to aid in the eradication of head lice. However, it is only useful when used alongside medication.

  • Wash clothing in very hot water of at least 130ºF (54.4ºC) and then follow with drying at high heat as this will kill the lice on the items.
  • Seal items that cannot be washed in plastic bags and the lice will die since it cannot feed. These items should be sealed for at least 2 weeks.
  • Vacuum the house frequently to remove lice from the living environment. This can help prevent the spread of the lice to others in the house and recurrence once the lice as been eradicated.
  • Avoid sharing personal items like combs and towels as this expedites the spread of lice from one person to another and may lead to recurrence.
  • Certain household products like mayonnaise and petroleum jelly may be applied to the scalp overnight to smother the lice but this should not be used in place of prescription medication.
  • Natural plant oils like tea tree oil may kill lice but the studies verifying its effectiveness have been done on small groups. The exact dose and potential toxicity of these substances have not been conclusively established.



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