Skip to main content

Chrysanthemums, Pyrethrin, and Getting Rid of Head Lice

Linda Crampton has an honors degree in biology. She is interested in chemicals from other organisms and their benefits to the human body.

An Annoying Problem

Head lice have lived on human scalps since ancient times. They are a common and very annoying parasite. Although they don't cause disease (as far as we know), they can be extremely irritating. The flowers of some chrysanthemum species contain an insecticidal material known as pyrethrum. One of the active ingredients in this material is a chemical called pyrethrin. The chemical is useful because it kills insects but is relatively safe for humans and pets compared to other insecticides. It's a common ingredient in lice treatments.

Unfortunately, although pyrethrin has been very effective at getting rid of head lice in the past, the insects are becoming resistant to the chemical. Pyrethrin is still a popular treatment for lice problems, but sometimes other control methods are needed. There are potential problems or difficulties with these methods, however. We really need a new treatment that is effective, convenient, and safe.

Although the word "pyrethrin" is often used in the singular, multiple varieties of the chemical exist. This is why the word is sometimes used in its plural form.

Chrysanthemums containing ray florets that hide the disk florets

Chrysanthemums containing ray florets that hide the disk florets

Chrysanthemum Facts

Chrysanthemums, or "mums", belong to the family Asteraceae and the genus Chrysanthemum. The family is also known as the Compositae. This name reflects the fact that the flower is technically a composite made of smaller flowers, which are sometimes known as florets. There are two types of florets. The disk florets are located in the centre of the flower and don't have petals. The ray florets surround the disk florets and each contain one petal.

Mums are beautiful and popular plants. Their flowers have lovely colours and patterns and take many different forms. Some chrysanthemum flowers are flat and resemble daisies. Others have multiple layers of ray florets that are upturned and hide the disk florets. Some flowers are almost globular and look like buttons or pom poms. In some species, the ray florets are narrow and tubular. This makes the flower look like a spider.

The genus is the first word in the scientific name of an organism. Some biologists think that the plants that produce pyrethrin should be placed in the genus Tanacetum instead of the genus Chrysanthemum.

The Dalmatian chrysanthemum is the main source of pyrethrin.

The Dalmatian chrysanthemum is the main source of pyrethrin.

Pyrethrum and Pyrethrin

The chrysanthemum that is generally used for pyrethrin production is Chrysanthemum cinerariifolium. Its common name is the Dalmatian chrysanthemum. Some people may not realize that this plant is a chrysanthemum because its flower looks like a white daisy and its leaves are finely divided like those of some ferns.

The Persian chrysanthemum or painted daisy (Chrysanthemum coccineum) is also used as a source of pyrethrin. It contains a much lower content of the chemical than its relative, however. Its flower resembles a daisy and is white, pink, or red in colour.

Chrysanthemums whose flowers look like daisies and produce an insecticide are sometimes known as pyrethrums because they were once classified in the genus Pyrethrum. The raw insecticidal material produced by the plant is also known as pyrethrum. The material contains the chemical named pyrethrin.

Both dried and powdered chrysanthemum flowers and an extract obtained from them are used to kill insects. The pyrethrin is located in the seed cases of the flowers. In some countries, pyrethrums are an important cash crop due to their ability to make a relatively safe insecticide.

The Persian chrysanthemum or painted daisy produces less pyrethrin than the Dalmatian chrysanthemum.

The Persian chrysanthemum or painted daisy produces less pyrethrin than the Dalmatian chrysanthemum.

Pyrethrin Action, Uses, and Effects

Pyrethrin is a neurotoxin for insects. It interferes with the normal functioning of an insect's nervous system, paralyzingly the animal and often killing It. The chemical kills other insects besides lice. It's appreciated for its safety for mammals (when used in recommended amounts) and the fact that it's broken down by light and air. In general, it doesn't persist in the environment after use.

Scroll to Continue

Read More From Remedygrove

Pyrethrin is often mixed with piperonyl butoxide in insecticides. The latter chemical acts as a synergist. A synergist doesn't produce a benefit by itself but makes another substance more effective. Enzymes in a louse's body normally break down pyrethrin, which may allow the insect to recover from a treatment. Piperonyl butoxide causes the chemical to stay intact for long enough to produce a permanent effect.

Pyrethrin is often used as a lice treatment for pets as well as humans. It has a very low toxicity in humans and other mammals and at recommended concentrations usually creates no problems. Some people experience an allergic skin reaction when they are exposed to the chemical, though. Inhaling a high concentration of pyrethrin can cause breathing difficulties and nausea. In test animals, very high concentrations have produced convulsions and paralysis.

Head Louse Facts

A head louse has the scientific name Pediculus humanus capitis. Lice are parasitic insects that feed on human blood. They have no wings and can't fly or jump. Instead, they crawl from place to place. Like other insects, they have three pairs of legs. Each leg ends in a claw, which resembles a hook. The claws enable a louse to cling to a hair. The females are slightly bigger than the males.

Head lice pierce our skin with their mouth parts and inject saliva containing an anticoagulant to encourage blood flow. They feed on small amounts of blood several times a day. Though the blood loss doesn't seem to affect us, the insect's saliva often triggers an allergic reaction. An itch is a major part of this reaction. People differ in their sensitivity to the saliva, however. For some people, the itch is intense and develops quickly. For others, it doesn't appear until several weeks after the arrival of the first louse and is milder. Some people don't experience an itch from a lice infestation.

The body louse is a close relative of the head louse but belongs to a different subspecies. Its scientific name is Pediculus humanus humanus. According to the Institute of Food and Agricultural Services at the University of Florida, head lice are more common in children and body lice are more common in adults.

Life Cycle of a Head Louse

A nit is the egg of a head louse. Nits are very small and are white or yellow in colour. They can be mistaken for dandruff. The female louse deposits the nits at the base of the hair shafts next to a person's scalp, cementing them to the hair with a glue. The nits hatch in about a week.

A tiny nymph emerges from a nit. The nymph looks like an adult head louse but is much smaller. The empty nit stays in place, so if someone is exploring the hair of someone with head lice, the nits that they find may be full or empty.

The nymph molts to form the slightly larger second nymphal stage. This in turn molts to form the larger third nymphal stage. The third nymph molts to form the adult house louse. The time period from nit hatching to the appearance of the adult is generally around nine to twelve days.

How Do Head Lice Spread?

Lice are spread by head-to-head contact or by the transfer of an item that has been in contact with an infested person's head. Example of these items include hats, scarves, combs, hairbrushes, pillows, and headphones. The items shouldn't be shared in case someone has a lice infestation. As the Mayo Clinic quote mentions below, though, there is one exception to this rule.

Head lice can affect people of any age but tend to infest children that form close and interactive groups, such as those formed in day cares and classrooms. A relatively new method of spreading lice has arisen due to the popularity of taking selfies. Children and teenagers often bring their heads together to take group selfies, allowing lice to crawl from one head to another.

A worry about head lice transmission is not considered a good reason to avoid sharing protective headgear for sports and bicycling when sharing is necessary.

— Mayo Clinic

A nit of a head louse; the nit was photographed after a lice treatment and is dead

A nit of a head louse; the nit was photographed after a lice treatment and is dead

Possible Symptoms of an Infestation

A head louse infestation can cause several signs and symptoms.

  • Itching is often the most common symptom.
  • The affected person may also experience a crawling or ticking sensation.
  • When someone examines the scalp of a person with head lice, they may see red spots.
  • White nit cases may be visible. These don't necessarily indicate an active infestation, however. They may be remnants of a previous one.
  • Some people don't experience any symptoms from an infestation.

The Mayo Clinic recommends that someone is checked by a doctor if a head louse invasion is suspected in order to avoid unnecessary treatment. Dandruff, scabs, dirt, and residue from shampoos and other hair products may be mistaken for lice or nits. Hair casts may also be mistaken for the insects. A hair cast is material dislodged from the surface of a hair.

Becoming infected by head lice doesn't mean that a person has poor hygiene. Anybody can get lice.

Pyrethroid Treatment

Pyrethrin is frequently found in head lice shampoos and treatments. It's been a mainstay treatment for getting rid of lice for a long time. Permethrin is a synthetic version of pyrethrin and is also a common ingredient in lice treatments. Pyrethrin and permethrin are known as pyrethroids. Pyrethroids kill adult lice but not nits. Other insecticidal chemicals are available for treating an infestation. These may not be as safe for humans, however.

Scientists say that although pyrethroids were once very successful at killing lice, they have lost some of their effectiveness due to the development of resistance in the insects. Animals in a species vary genetically. Some lice may possess a gene or combination of genes that makes them resistant to pyrethroids. When these lice reproduce, they pass some of their genes to their offspring, enabling some of the offspring to resist the insecticide, too. As the insecticide kills the lice that are susceptible to damage by pyrethroids, a population of resistant insects gradually becomes dominant.

While different sources seem to agree that the effectiveness of pyrethroids has decreased recently, they disagree about the extent of this decrease. The current effectiveness may depend on the identity of the pyrethroid and on the genetic makeup of the head lice in a community. It may also depend on how carefully the application instructions are followed, as the John Hopkins reference below suggests.

Products that kill lice are often referred to as pediculicides.

Safety When Using Lice Shampoos

A lice shampoo, lotion, or cream containing pyrethrin should be kept out of a person's eyes. The chemical may irritate both the eyes and the scalp. It's often considered to be the safest insecticide to use, however, and is usually available over-the-counter (that is, without a prescription). The instructions on the packet regarding the amount of product that should be used, the treatment method, and the frequency of application should be read carefully.

Some lice treatment products contain a different insecticide and are generally available only by prescription. The safety of each of these products should be investigated. It's advisable to discuss a product's safety with a doctor or a pharmacist.

The Wet Combing Treatment for Head Lice

One treatment for head lice that can be effective and doesn't require an insecticide is the wet combing method. In this treatment, a large amount of conditioner is applied to the hair. A fine toothed metal lice comb is then run though the hair to pick up lice and nits. A lice comb has a special design. It's not simply an everyday comb with fine teeth. Lice combs are available at drug stores.

The process of wet combing can be boring for the person being treated, especially if that person is a child, so it's good if they have something to entertain them while they're sitting down. Good lighting is needed so that the person doing the combing can see the hair and scalp clearly. The process involves carefully combing a section of hair and then pinning it out of the way so that another section can be combed. The comb needs to be wiped with a tissue before cleaning a new section of hair. The tissues must be carefully disposed of after use.

The wet combing method needs to be repeated every three to four days for around two weeks in order to remove newly hatched lice. It's more time consuming and requires more effort than using a chemical method to control lice, but it has important advantages. It avoids the application of an insecticide to the scalp. It can also overcome the problem of diminishing effects of pyrethroid treatment due to lice resistance.

Several natural creams, oils, and liquids are said to kill head lice. Health experts say that there is little evidence that these treatments work. The animals don't suffocate or drown easily. The experts say that the wet combing method of removing head lice can be effective, however.

Preventing Another Infestation

Head lice don't live for long once they are removed from the human body. Adults require a meal of human blood within two days of their last meal. Nymphs which have just left the egg require a blood meal within twenty-four hours. Eggs require the heat of our body in order to hatch.

The CDC (Centers for Disease Control and Prevention) makes several suggestions with respect to dealing with lice. It says that all clothing, bedding, and towels used by someone with lice in the two-day period before treatment starts should be washed in hot water and dried by hot air. If the items can't be washed, they should be dry cleaned or sealed in a plastic bag for two weeks. Combs and hairbrushes should be washed in very hot water. Floors and furniture such as sofas should be vacuumed, since we shed hairs on a daily basis. These hairs may have lice attached to them.

Lice have been part of human lives for thousands of years. It looks like we'll be fighting them for many years to come. Hopefully, new and improved treatments for head lice will appear soon.


  • Information about head and body lice from the University of Florida
  • Head lice facts from the Mayo Clinic
  • Facts about treating head lice from the Centers for Disease Control and Prevention
  • A head lice report from the American Academy of Pediatrics (The information about corrections in the report should be noted. Clicking on the link in the information takes the reader to a page showing the corrected sections.)
  • Pyrethrins General Fact Sheet from the National Pesticide Information Center
  • A report about the reduced effectiveness of pyrethroid treatment for head lice from the CBC (Canadian Broadcasting Corporation)
  • Head lice treatment from John Hopkins Medicine
  • Information about wet combing from the NHS (National Health Service)

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2014 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on March 02, 2015:

Thanks for the comment and for sharing the interesting information, Peg. I pity a person who discovers that they have head lice at a hairdresser and also has to leave with an incomplete hair cut!

Peg Cole from North Dallas, Texas on March 02, 2015:

This really creepy creature is quite durable. The fact that the natural treatment is losing effectiveness is not good. Those photos are incredible. Yikes. No wonder they cause intense itching.

We learned about head lice in cosmetology training but not to this extent. Very interesting. By law a hair stylist must discontinue any type of service once head lice are discovered even if a hair cut is half finished.

Linda Crampton (author) from British Columbia, Canada on January 02, 2015:

What an interesting solution to the head lice problem! Thanks for sharing it, Rhonda. It sounds like it was a horrible situation for your student, but at least she found a way to get rid of the lice.

Rhonda Lytle from Deep in the heart of Dixie on January 02, 2015:

I had a high school student with really long hair, past her behind. She got them from some life skills students she was volunteering to work with. I'll never forget her crying. She was so upset. I got the treatment stuff at lunch and we did it after school. She lived on her own and had no family to help. After a few rounds of this, we still had not gotten rid of them and folks were calling for this poor girl to shave her head. While I hated she did it, dying her hair actually killed them all, the first time. My gorgeous blonde student went gothic black overnight but was lice free.

Linda Crampton (author) from British Columbia, Canada on January 02, 2015:

Thanks for sharing your experience, Cassandra. It sounds like it was very unpleasant! Head lice can be a big nuisance. I hope a better way to treat them is discovered.

Elizabeth Lynn Westbay from United States on January 02, 2015:

I had lice when I was a child resistant to everything I put on my head. It was a nightmare. Finally I had to sleep with my head drenched in olive oil and wash out the little dead lice every morning. That and wet combing got me through it. It took like a week to kill the live ones and another week to get rid of all the nits but my mom and I finally got rid of the darn things. It was a nightmare I wouldn't wish on my enemy.

Linda Crampton (author) from British Columbia, Canada on January 01, 2015:

Thank you very much for sharing your experience, pstraubie. I appreciate your comment and the angels a great deal!

Patricia Scott from North Central Florida on January 01, 2015:

I had no idea. When I was still a teacher of precious children, we had head check every Friday and the dolls who had lice went home till the problem was taken care of.

I had no idea that there were these sources to help treat an outbreak.

Angels are on the way to you this afternoon. ps

Linda Crampton (author) from British Columbia, Canada on January 01, 2015:

Thank you very much for the comment and the share, ologsinquito. I appreciate your vote as well.

ologsinquito from USA on January 01, 2015:

I feel so fortunate my children never picked these up. What a nuisance. Great article. Voted up and shared.

Linda Crampton (author) from British Columbia, Canada on November 23, 2014:

Hi, Deb. Yes, holistic medicine can be useful. Studying medicines in plants is an interesting topic. Thanks for commenting.

Deb Hirt from Stillwater, OK on November 23, 2014:

This was very good. Mums and other natural plants are wonderful in an assortment of treatments. I recall having a naturally made cough medicine that made me well in three days, as opposed to a standard cough medicine that too more than twice as long. Let'd hear it for holistic medicine!

Linda Crampton (author) from British Columbia, Canada on November 10, 2014:

Thanks for the comment, vespawoolf. I appreciate your visit.

Vespa Woolf from Peru, South America on November 10, 2014:

I´m always fascinated with natural treatments. I had no idea the components in these flowers interfere with the life cycle of a louse. I also think wet combing is a good option for ridding a child of nits. Very interesting!

Linda Crampton (author) from British Columbia, Canada on November 02, 2014:

Hi, poetryman6969. No, the topic of head lice isn't pleasant for people who are infested with them! Thanks for the comment,

poetryman6969 on November 02, 2014:

Not a pleasant subject but thanks for spreading the news.

Linda Crampton (author) from British Columbia, Canada on October 29, 2014:

Hi, Cynthia. Thanks for sharing such an interesting, insightful and kind comment! I appreciate your visit very much.

Cynthia Zirkwitz from Vancouver Island, Canada on October 29, 2014:

Hi Linda-- This is an excellent hub on lice, with a very nice presentation. I worked as a social worker in a day care for a few years. There were many "infestations" and a lot of attention to protocol, but I'm pleased to say I didn't get lice myself. Nor did my children. But that doesn't mean we didn't get cavities, colds, or flea bites occasionally when our pets were infested. Disturbingly, more for some than others, humans live very closely with all kinds of parasites. We have much to learn from them, and you have done a fine job of teaching us. Thank you!

Linda Crampton (author) from British Columbia, Canada on October 28, 2014:

Thank you very much for the comment, Mel! Yes, many people think that having head lice has something to do with bad hygiene, but health experts say this isn't correct. Anybody can get head lice if they get close enough to the insects to enable them to climb on to the hair.

Mel Carriere from Snowbound and down in Northern Colorado on October 28, 2014:

Fascinating expose on head lice and its treatment. I remember getting checked as a child, but we always thought only the ""dirty" kids got it. Great hub!

Linda Crampton (author) from British Columbia, Canada on October 27, 2014:

This is an interesting story, Nancy. I can understand why your mother and you were so frustrated! Thank you very much for the comment and for sharing the information.

Nancy Carol Brown Hardin from Las Vegas, NV on October 27, 2014:

Made my head itch before I got through the first paragraph. EWWW! When I was 6 years old and in first grade in Chicago, IL, my mother discovered I had lice. At that time there was a treatment known as blue ointment, and she slathered that on, used the lice comb, and I was a miserable little girl. We finally got rid of them, only to have me come down with them again inside of two weeks. Obviously someone as school was carrying them, so the school nurse had to inspect everyone. Those who had head lice were sent home with a note to their parents. It seemed like an epidemic at the time, but finally we were all louse free. Whew! I remember all this, because it was so traumatic for my poor mother, who never let a speck of dirt collect in our house or on our bodies. As you might expect, the first time was bad enough, but she was furious the second time around! Lots of good information here, hope it gets out to lots of folks who may need it.

Linda Crampton (author) from British Columbia, Canada on October 27, 2014:

Thanks for the visit and for sharing the tip, Susan!

Susan Zutautas from Ontario, Canada on October 27, 2014:

I have an itchy head after reading your hub :) When my boys were small I always used tea tree oil and tea tree oil shampoo to kill the head-lice.

Linda Crampton (author) from British Columbia, Canada on October 26, 2014:

I hope you never get head lice too, Sandy! Thanks for the visit.

Linda Crampton (author) from British Columbia, Canada on October 26, 2014:

Thank you very much, DDE. I appreciate your comment and vote.

Sandy Mertens from Frozen Tundra on October 26, 2014:

I am itchy just reading this. Hope I never get it but interesting to learn about how these flowers help.

Devika Primić from Dubrovnik, Croatia on October 26, 2014:

Hmm! I knew of someone who had head live and I had to stay away from them. The comb sometimes had the live too. Great hub on this subject. You have such interesting hubs. Voted up!

Linda Crampton (author) from British Columbia, Canada on October 23, 2014:

Hi, Bill. Thank you very much for the comment. I hope you never experience a head lice infestation!

Bill De Giulio from Massachusetts on October 23, 2014:

Thankfully I've never had head lice. Those pictures of them give me the heebie jeebies :) Very interesting hub Linda. This was quite an education.

Linda Crampton (author) from British Columbia, Canada on October 22, 2014:

I hope researchers discover a better way to get rid of lice, too! I certainly wouldn't want to have head lice, and I sympathize with those who do. If I forget about the irritation that they produce, though, I think that head lice are interesting creatures! Thank you for the comment, Faith.

Faith Reaper from southern USA on October 22, 2014:

You have me scratching my head as I write this comment! Useful article, but just looking at the photos turns my stomach, as they are so disgusting to me. They are hard to get rid of for sure. Interesting about the chrysanthemums. I do hope they come up a better way to get rid of lice and soon!

Linda Crampton (author) from British Columbia, Canada on October 22, 2014:

Thanks for the comment, Bill. I appreciate it. I've never had head lice myself, but I've known people who have. A lice infestation isn't very pleasant!

Linda Crampton (author) from British Columbia, Canada on October 22, 2014:

I hope you and your family never get a visit from head lice, Kim! They can be a big nuisance. Thanks for the visit and the comment.

Bill Holland from Olympia, WA on October 22, 2014:

You always have the most interesting information. I am happy to report I've never had head lice. :)

இڿڰۣ-- кιмвєяℓєу from Niagara Region, Canada on October 22, 2014:

I'm already scratching my head! Lord, but they are disgusting. And are a lot of work to get rid of. Yuck. I can do without them, that's for sure. I do vaguely remember hearing about the chrysanthemum flower years ago and how it was used for lice. Hopefully, lice will stay out of this household... **Kim frantically knocking on wood**

Related Articles