Headlice and Essential Oils

Lowana Veal is a biologist who has carried out experimental work with essential oils. She has also written a number of articles on complementary health issues

From time to time people ask questions about essential oils and headlice. As a result, discussion ensues, but the information imparted is not always correct and some recipes for use of oils comes from books rather than successful practice. This page will be a mixture of general information on lice and their control, discussion of oils commonly purported to be useful against lice, and oils that I tested on lice in the laboratory which work very effectively. Based on these results, I shall list other possible oils that can be used and a protocol for lice treatment. But first some general facts.

Lice biology

• The life cycle of the louse is about 4 weeks. Approximately 8 days are spent in the egg stage, which is the hardest stage to kill. The eggs then hatch into tiny lice (first instar nymphs), then into second and third instars and finally into adults. Female lice are larger than males.
• Lice eggs are opaque. If they are clear, it means the lice have already hatched out.
• Healthy lice and eggs are found only within 1 cm of the scalp. They are transmitted by head-to-head contact, not by combs, brushes or furniture, and neither do they live in school buildings or home carpets.
• Head lice are not a sign of bad hygiene. They prefer clean hair to dirty hair.

Control

• It may take several months for a person to become sensitised to the presence of lice, so when treating the affected person it is also important to check all people who have been in close contact with the person during that time. Look at the roots of the hair for lice, eggs, lice faeces (black specks) and cast skins. Faeces and skins may also be found on pillows of the affected person.
• Treat only those people who show signs of lice.
• Make sure that enough of the treatment product is used, and follow the instructions as to how long to keep it on the hair. Do not leave it on for less than the suggested time.
• Shampoos in general will not kill lice as the solution is too weak by the time the extra water needed for hair-washing has been added. This applies to both conventional lice shampoos and those containing essential oils. It is much better to use an aqueous or alcoholic lotion or a conditioner base.
• Comb the hair well afterwards to remove dead and dying lice.
• Repeat the treatment after a week, unless told otherwise.
• If the protocol states that the procedure should be repeated every 2 days, or even more often, this implies that the treatment is not effective on lice eggs.

headlice and Essential oils

NB: Common English names have been used in the text to make for easier reading. However, it is important to specify the Latin name too. Here is a list of common and Latin names of the oils mentioned in the text:

Existing recipes for home use

Although many insecticidal preparations are available for treating headlice, most of these contain malathion or pyrethroid products which seem to be becoming less effective, possibly because headlice have become resistant to the insecticide. Also, many people do not like to put insecticidal products on themselves or their children and instead resort to practices such as combing the hair and removing any lice and eggs that are found.

As far back as the first century AD, Diascorides described the use of Juniperus communis, juniper, as a treatment for headlice. Later, in 1694, John Pechey noted the use of lavender, as a lousicide.¹ More recently, a number of aromatherapy books have contained recipes for headlice. Worwood ² states that 27 drops each of rosemary, geranium and lavender in 25 g white beeswax and 50 ml caster oil will form an ointment that can be used on the scalp overnight. Dye ³ includes several recipes for headlice treatment. An oil mixture made from 25 drops tea tree, 15 drops geranium, 15 drops eucalyptus and 20 drops lavender to 100ml carrier oil can be massaged into the scalp and hair, left for one hour and rinsed off. This procedure should be repeated every two days for a period of 7-10 days, and may be repeated again at two weeks. Other recipes she mentions are an equal blend of rosemary, geranium, lavender, eucalyptus and lemon in carrier oil, and also a mix of equal proportions of rose, geranium, lavender and tea tree in a carrier oil. With both these blends the mixture is rubbed into the scalp, left for two hours and washed off. The process is repeated three times over 10 days, left for a week and then repeated.

Kusmirek ⁴ recommends geranium, lavender and tea tree as a scalp oil for headlice, while Watson ⁵ suggests a two stage technique in which a blend of 8 drops eucalyptus, 10 drops tea tree and 7 drops thyme are added to 50 ml jojoba oil, applied to the hair and scalp, left for two hours, washed off with shampoo and then towel dried. A rinse mixture is then applied by adding the same essential oils to a half cup of vodka; this mixture is then poured through the hair and left for 30 minutes. During this period the hair is combed to remove any lice present. The hair is then rinsed with warm water.

Price ⁶ only recommends cinnamon and oregano as lousicidal oils, but does not suggest any recipes for home use. Valnet ⁷ suggests that cinnamon, eucalyptus, geranium, lavender, lemongrass, oregano, rosemary and thyme can all be used for headlice. An ointment made from 15 drops each of oregano, lemongrass, geranium and thyme in 5 g melted clear wax and 85 g Vaseline is recommended for the treatment of lice, but no instructions are given as to how it should be used.

Lawless ⁸ mentions that cinnamon, eucalyptus, geranium, lavandin, spike lavender, parsley, pine, rosemary and thyme can all be used for lice, while Sellar ⁹ states that aniseed can be used to control them. Finally, Gauthier et. al.¹⁰ have demonstrated the effectiveness of myrtle essential oil on lice, in both laboratory and clinical trials.

Scientific testing

Apart from the French paper by Gauthier et. al.¹⁰, none of the authors mentioned above offer scientific proof of the effectiveness of the oils and it is unclear on what basis they have formulated their recommended blends. Much of what follows is based on my research on essential oils of aniseed, oregano, cinnamon leaf, tea tree, red thyme, rosemary, pine and three blends. I wasn't interested in anything that didn't kill the eggs as well as the adults. One of the proprietary chemical products on the market consistently kills only 67% of the eggs, but I don't think that's good enough so wasn't interested in anything less than 80% kill.

The lice were dipped in the appropriate solution, at a concentration of 2 drops EO to 10 mls solvent, blotted dry, and left overnight in an incubator. Then they were shampooed with a normal shampoo, and then a rinse mixture of 2 drops essential oil to 100 mls of vinegar/ water (50:50) was poured over them. The same procedure was carried out on lice eggs, on strips of gauze.

The blended oils that worked best were a 50:50 mixture of tea tree and cinnamon leaf (not cinnamon bark), which killed all the lice and 96% of the eggs; and peppermint and nutmeg at a 30:70 ratio, which killed 82% of eggs and all the adults. The solvent in these cases was 40% alcohol. A rosemary/red thyme mixture was also tried, but didn't work well. Also, without the rinse the oils were hopeless against the eggs.

I then tried various oils by themselves. I tried pine as that is supposed to be an insect repellant and I thought it might work. However, both it and rosemary had lower egg mortalities than the controls, and only killed 78-79% of the adults. I abandoned any more work on them.

I also tried red thyme (thymol chemotype), tea tree, cinnamon leaf, oregano and aniseed by themselves. I tried aniseed as it is supposed to be effective against lice in herbal medicine in herbal medicine in herbal medicine, but, as with the herbs wormwood and quassia, I found that the herbal infusion of aniseed was not effective.

Not all the oils were tested at the same time. Oregano had 100% mortality with both eggs and adults when dissolved in alcohol, and so did aniseed and cinnamon leaf, thought the control mortality for the egg results in the last two oils was abnormally high. Red thyme had 84% mortality with adults and 92% with eggs, though it was in the same batch as aniseed and cinnamon so the egg results may not be accurate. Tea tree had 93% adult mortality and 83% egg mortality. A rinse was used in all cases. The rinse by itself is ineffective.

I also tested some of the oils in water rather than alcohol, and found that aniseed still killed 100% of the adults and eggs, and oregano killed 99.3% of eggs and 100% of adults. Red thyme killed all the adults but only 51% of eggs; tea tree killed 94% of adults and 59% of eggs, and cinnamon leaf killed 86% of adults but only 26% of eggs.

I had to shake the mixtures each time because they weren't particularly soluble. It may be possible to use jojoba oil as a solvent, which will deal with the solubility problem. Jojoba oil is said to dissolve sebum¹¹ which means that the oils may penetrate the insect cuticle faster. Other carrier oils could also be tried, as the insect cuticle is generally soluble to lipids and lipid-soluble compounds¹². I also found that using olive oil overnight on lice eggs prevented the majority of the eggs from developing, but it did not work so effectively with adult lice. Alcohol is known to increase the penetration rate of the cuticle.

The effective components of the oils are likely to be phenols, phenolic ethers, ketones and 1,8-cineole, as these constituents were common to all of the essential oils tested. These components have also been identified as effective anti-parasitic components by Penoel and Franchomme¹³ in L'Aromatherapie Exactement. In addition, some aldehydes and sesquiterpenes may also be effective. A French research team¹⁰ had found previously that myrtle oil was effective against lice, and attributed the effective ingredients to cineole and, to a lesser extent, alpha-pinene and linalool.

Practical aspects

If one knows the constituents of essential oils, it may be possible to predict other oils that may also be effective as a louse control agent. Oils containing phenols, ketones, oxides, or aldehydes may be effective. Oils which have a high phenol content include summer savoury (carvacrol), winter savoury (carvacrol or thymol), and clove bud (eugenol), while fennel contains the phenolic ether trans-anethol. Ketones are found in hyssop, sage and caraway, and the oxide 1,8-cineole is found in Spanish marjoram, eucalyptus, cajuput and niaouli, as well as myrtle. Lemongrass may also be effective as it contains the aldehyde citral.

So how should the oils be used? Based on my experiments, you could try the following: use a base of 40% alcohol (vodka would do, or grain alcohol), and add any of the effective EOs mentioned above at a rate of 10 drops to 50 mls. Rub that into the scalp and leave on overnight then wash off in the morning with shampoo. Then put a rinse through the hair using 2 drops of the same EO/ EO mix that you used originally added to half a pint (100 ml) of 50:50 vinegar and water. Repeat the whole process a week later. If you don't want to use alcohol as the solvent, jojoba oil or another carrier oil may also be worth trying, as mentioned earlier.

Do book recipes work?

Many aromatherapy recipes for lice contain either/or lavender, geranium or rosemary. I did not try lavender or geranium in the series of tests I conducted, so I cannot predict whether they would work or not. I was surprised that rosemary did not work, as it often contains cineole. Maybe some chemotypes of rosemary would work, but unless you obtain a chemical breakdown of an oil when buying it, is impossible to know which chemotype is being supplied.

References

¹ Tisserand, R (1988) Aromatherapy for everyone. Penguin, London

² Worwood, V A (1991) The fragrant pharmacy. Bantam, London

³ Dye, J (1992) Aromatherapy for women and children. C.W. Daniel, Saffron Walden, Essex

⁴ Kusmirek, J (1993) Aromatherapy for the family, 4th ed. Wigmore, London

⁵ Watson, F (1995) Aromatherapy blends and remedies. Thorsons, London

6 Price, S (1994) Practical aromatherapy, 3rd ed. Thorsons, London

⁷ Valnet, J (1982) The practice of aromatherapy. C.W. Daniel, Saffron Walden, Essex

⁸ Lawless, J (1992) Encyclopedia of essential oils. Element, London

⁹ Sellar, W (1992) Directory of essential oils. C.W. Daniel, Saffron Walden, Essex

¹⁰ Gauthier, R, Agoumi, A, Gourai, M (1989) Activité d'extraits de Myrtus communis contre Pediculus humanus capitus. Plantes médicinales et phytothérapie 23(2): 95-108

¹¹ Price, S (1993) Shirley Price's aromatherapy workbook. Thorsons, London

¹² O'Brien and Fisher (1958) Permeability and liposoluble compounds. Journal Economic Entomology 51, 169ff

¹³ Penoel, D and Franchomme, P (1991) L'aromathérapie exactement. R. Jollois, Limoges

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This research by Lowana Veal was first published in Complementary Therapies in Nursing & Midwifery (1996) 2: 97-101 and The Aromatherapist (1996), 3(3) 3: 4-13.

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