Head Lice ~ Identifying, Treating and Prevention Tips

by Dr. Jennifer Ryan, Pharmacist 


What is Head Lice?

Head Lice (pediculus humanus capitis) are tiny insects that live close to the human scalp. We are their only source of food.  They cannot survive on pets or inanimate objects for longer than 12-24 hours.  There is no evidence that lice can be spread through any way other than head to head contact.  They do not jump or fly, they only crawl.  Sharing combs, hats, hairbrushes, helmets and headphones is generally discouraged.

Who can be infected? 

Anyone can be infected.  There is no more shame in having lice than there is catching a cold.  Infestation has nothing to do with hygiene or social status.  Head lice are particularly common in children of primary school age and more common in girls than boys.  Schools, daycares, summer camps are common places where head lice can be transmitted.

How are head lice diagnosed?

Head lice can be diagnosed if a living louse is found on the head.  Adult lice are visible and are black, brown or grey-white insects.  No treatment should be should be carried out unless a live louse is found.

Head lice have three forms:  eggs (nit), nymph, and adult.  Eggs are laid at the base of the hair shaft, closest to the scalp.  Eggs are firmly attached to the hair-this helps differentiate them from dandruff which comes out easily.  They are about the size of a knot in a thread.  They are translucent when laid, and white after hatching.  Eggs containing unhatched, dead lice take on a dark brown color.

Using a fine tooth comb (0.2-0.3 mm apart) can help detect lice. It is three times more effective than visual inspection alone. Start at the crown and comb down, checking the comb for lice after each stroke.

Who should be treated?

Anyone found to have living lice should be treated.

What treatments are available?

Chemical Insecticides:  These are more traditional treatments and include:  Pyrethrins with piperonyl butoxide (R&C Shampoo+Conditioner or Pronto) and 1% permethrin (Kwellada-P Cream Rinse or Nix Creme Rinse).  These agents cause neurotoxicity to the lice.  Growing resistance to neurotoxic insecticides has increased the number of treatment failures that we see.  The resistance patterns are unknown in NB, however resistant mutations were found in most samples from Ontario, BC and Quebec. Resistance increases when these agents are not repeated properly as per manufacturers’ instructions, allowing the strongest insects to survive and pass on their genes.  Good old natural selection!  Local irritation is the most commonly reported side effect with chemical insecticides.  Parents often express concern about exposing their children to chemical insecticides, however, to date, there has been no conclusive evidence that the currently marketed agents cause any harm to humans.  There may be a cross-sensitivity if you are allergic to ragweed or chrysanthemum.

Physical Insecticides:    These are the newest agents to the market.  There are two products on the Canadian market.  Dimeticone Solution Spray (NYDA) and isopropyl myristate solution (Resultz rinse).  These have both been found to be more effective than traditional chemical insecticides in randomized controlled trials.  NYDA works by entering and sealing respiratory systems of lice, nymphs and eggs and basically suffocating the insects.  Resultz rinse, in contrast, dissolves the exoskeletons of the insects and dehydrates the live lice and nymphs.   Treatment and repeat treatment of each of these products are recommended as per the manufacturer instructions to ensure cure.  The nice thing about the physical agents is that they don’t incur resistance.  Local irritation is the most common adverse effects with physical agents. Safety in very young children and pregnant or lactating women is unknown.

Herbal or natural approaches:  Among the substances that have been used to eradicate head lice are occlusive agents such as Vaseline or mayonnaise, or herbal products such as tea tree oil, eucalyptus oil or vinegar.  There is a very small study that found a combination of tea tree oil and lavender to be effective when compared to chemical and physical treatments.  This is encouraging, but it should not yet be considered a reliable method.  It has no effect on unhatched eggs.  For most of these natural products, data on toxicity and efficacy from randomized clinical trials are lacking.  The Canadian and American pediatric societies do not endorse the use of “natural” treatments in the battle against lice.

Mechanical Methods:  There is evidence that mechanical removal of lice can be effective if performed properly.  But it takes some real commitment.  This may be the best option for very young children, as most commercial products are not recommended for children under 2. This may also be an option for pregnant women.  In most cases, I would recommend combining manual removal of nits in combination with a commercial treatment to ensure success.  Combing technique includes wetting the hair and adding conditioner.  Combing the whole hair with a fine-toothed nit comb.  Check for lice after each stroke. Continue combing until no lice/nits are found.  Generally, this takes 10-30 minutes per session but can be longer for very long and thick hair. Rinse out the conditioner and perform the combing again.  Conduct the entire procedure 4 times (every 3-4 days) over 2 weeks or until no lice are found on three consecutive sessions.

What About Furniture, Clothing, Bed sheets, Personal Items etc.?

Excessive detail to cleaning items such as furniture is no longer considered vital, however personal items such as hats, pillow-cases, brushes and combs should be cleaned in hot water (>50 degrees Celsius).  Items that are difficult to wash can also be placed in an occlusive bag for two weeks to kill lice and nits.

Can I Prevent Head Lice?

Although Head Lice can be an annoying problem, it is common to all.  The best way to prevent head lice transmission is to play your part in doing regular inspections of your children and family members.  Check children when they come home from camps or overnight trips.  During outbreaks, keep hair tied back or braided to minimize transmission and teach your children not to share personal items like hats and hairbrushes.   If and only if lice are detected, treat immediately. Beyond this, there is insufficient evidence to support interventions to prevent lice.

For additional information, contact your pharmacist or NB Department of Public Health.



Dr. Jennifer Ryan, BSc. Pharm, Pharm D, ACPR, FCSHP

Jennifer received her Bachelor of Pharmacy in 1999 from Dalhousie University, Halifax, Nova Scotia and completed the Canadian Hospital Pharmacy Residency Program at the Hospital for Sick Children in Toronto, Ontario in 2000. She received her Doctor of Pharmacy in 2006 from the University of Florida.

From 2001-2014 held several positions as a hospital pharmacist including: Pharmacy Research and Education Coordinator, Clinical Manager, Pharmacy Residency Coordinator and Pharmacy Practice Leader in Nephrology. She has held an adjunct faculty position with Dalhousie University since 2005. Jennifer’s research interests have included areas of disease prevention, medication adherence and pharmacy education. Jennifer has presented nationally and internationally.

Jennifer and husband Cory own and operate the Medicine Shoppe Pharmacy, in Grand Bay-Westfield where they live and raise their three children. They have a strong sense of community responsibility and are committed to improving healthcare access for their clients and neighbors.

You can find more valuable information at  www.facebook.com/themedicineshoppepharmacygrandbaywestfield


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