1. How did my child get headlice?
2. Why do headlice move from head to head?
3. Does combing and brushing control headlice and kill eggs?
4. Is Olive Oil treatment effective?
5. Should I treat myself to prevent infestation?
6. The lice are gone! Why is my child still itching?
7. Do pets transmit headlice?
8. How long does a treatment last?
9. Are eggs found 3cm away from the scalp dead?
10. When is a nit not a nit?
11. What is the difference between a non-poison and a "harmless substance"? 
12. Is killing headlice necessary?
13. Why do some head lice treatments fail?

1. How did my child get head lice?
Headlice is a highly communicable condition and there are a number of ways to contract it. 

• By contact with an already infested person. Contact is common during play, at school, and at home (slumber parties, sports activities, on a playground). 
• By wearing infested clothing, such as hats, scarves, coats, sports uniforms, or hair ribbons.
• By using infested combs, brushes, or towels.
• By lying on a bed, couch, pillow, carpet, or stuffed animal that has recently been in contact with an infested person. 

3. Does combing and brushing control lice and remove eggs?
No matter what chemical or naturally occurring product is used to kill live lice,  no treatment kills 100% of all eggs (nits), even if the label says otherwise! Therefore, there are only 2 ways to ensure a complete eradication of any headlice population. (1) retreat with an approved product in 10 days for newly hatched lice, which as eggs, escaped the original treatment, or (2) physically remove unhatched eggs. 
Systematic and diligent wet combing every day for 2 weeks (using plain water or hair conditioner) with a nit comb could eradicate a headlice infestation, depending on combing skills.  Some people have found that combing with a flee comb designed for pet animals works for them. (Frequent brushing and combing of dry hair may also control headlice by damaging them, although a trial in Bangladesh has shown this method to be unreliable). The natural-products anti-headlice cream, Electric Blue, is reported to facilitate egg (nit) removal, by denaturing the complex protein glue that sticks headlice eggs to the hair shaft.

4. Is Olive Oil treatment effective?
A State Health Department document, widely circulated by schools recommends olive oil as a ‘safe and effective way to kill head lice’. It is applied generously to the hair and left on for 8 hours or overnight, on 7 days in a 21 day period. This recommendation is presumably based on its supposed effect as a suffocating agent, or as an aid to nit-combing by lubricating the hair. The Harvard School of Public Health is usually quoted as the reliable source of this recommendation. In fact, Harvard advises of as many failures as successes in informal testing, and states ‘we do not recommend the use of olive oil (or other such substances) as a treatment for headlice’.  Harvard advises caution in the use of olive oil because it ‘may have associated hazards’. The heavy load of oil on the hair may require multiple shampooing with harsh detergents, causing scalp irritation. The editor of this website agrees with the National Pediculosis Association in its comments that “...if olive oil encourages people to avoid pesticides, then this is good. (but) there is no Harvard study to support the claim that olive oil kills lice...”  Footnote: the latest recommendation of the State Health Department in question is to use hair conditioner! 

5. My child has head lice. I do not.  Should I treat myself to prevent becoming infested?
No. Headlice resistance to treatments is encouraged by people trying to prevent infestation by prophylactic (preventive) use of anti-headlice products. Treat only if crawling lice, or nits (eggs) are seen within 5-10 mm of the scalp. However, anyone living with an infested person can get head lice. So, check people in the household for lice and nits every 2-3 days. 

6. The lice are gone! Why is my child still itching?
Head scratching, alone, is not an indication for headlice treatment, or re-treatment in the absence of live lice or eggs. However, as it is sometimes difficult to detect nymphs and newly laid eggs, and because no product kills all eggs, second treatments are routinely recommended. Head scratching soon after treatment could be due to itching of (a) sores caused by previous scratching, or (b) a temporary allergic reaction to headlice bites. This allergy can last up to 4-5 days after lice are eradicated. So, check the scalp. If infected sores are evident, get medical advice. If no infection is obvious, but you need relief from discomfort, use an antiseptic cream containing a local anaesthetic.

7. Do pets have or transmit head lice?
No. Head lice do not feed or live on pets so you cannot ‘catch’ them from pets or other animals. 

8. How long does a treatment last? 
Practically speaking, a treatment lasts only as long as it is in contact with the hair and scalp. Once it is rinsed out, in general there is no residual (long-lasting) action. A residual effect is claimed for some lice treatments. For example, if a malathion product is left on the hair for 6-12 hours, the compound may impregnate the outer surface of the hair shaft. However, one swim in a chlorinated pool and the residual effect is cancelled. In the case of permethrin the residual effect may last weeks - but treatment failures are now common! There are reports of various essential oils having a repellent- and a lice-killing effect, but we are not aware of any such products claimed to have a long lasting (residual) effect. 

9. Is it true that eggs found 3cm away from the scalp are dead?
Most expert opinion is that eggs found more than 10-15 mm (1 to 1.5 cm) from the scalp are either hatched or dead. It is true that eggs are mostly laid close to the scalp - but this depends on the climate. When the ambient air temperature is close to (or exceeds) body heat, a female louse may lay eggs anywhere along the hair shaft, because the eggs will not depend on body heat to incubate. Even in cooler climates, heads that are hotter and perspire more will generally have eggs further away from the skin than cooler drier heads. Furthermore, a long hair that lays across & contacts the scalp for several centimetres, could have viable eggs at any point along it.
These obvious, but widely unrecognised facts, could account for many puzzling re-infestations - especially in fair-haired people.

10. When is a nit not a nit?
When its a pseudo-nit.  Pseudo-nits may be mistaken for nits (eggs). On closer examination they may be dandruff, hair spray residue, or skin cells. These are easily removed whereas real nits are securely stuck to the hair shaft. The exception is the pseudo-nit known as a DEC (desquamated epithelial cells) plug which encircles the hair, and is sometimes hard to remove.

11. How do I to tell “non-poison” from “harmless substances”?
Okay, okay. Let's get technical! In Australia a poison is a substance that is listed in the Uniform Poisons Schedules. Everything else is deemed to be a “non-poison”. Consumers sometimes have a difficult task in interpreting this. For example, a State Health Department Head Lice pamphlet says "There are a number of alternative products on the market, such as tea-tree oil and sassafras oil. These have varying degrees of effectiveness." The Department also recommends the olive oil treatment.  Readers could consider that these three products are harmless, on the basis that because olive oil is a harmless edible oil, the other oils (as such, or ‘neat’) may also be used without hazard. The fact is that there is a very steep increase in toxicity and hazard from olive oil to sassafras oil. Although sassafras oil was traditionally used for scabies and is listed in the British Herbal Pharmacopoeia as a pediculicide, it is now inappropriate. It can be likened to recommending mercurials as topical anti-infectives. As advised elsewhere, small amounts of ingested sassafras oil are both neuro- and hepatotoxic. Larger doses can cause respiratory paralysis. The oil’s carcinogenicity due to its safrole content is widely acknowledged. Australian authorities (Talalaj & Czechowicz) on herbal remedies have stated about sassafras oil, “Even external use of the oil is hazardous because it can easily be absorbed through the skin and exert its general toxic effects.” In Australia, adoption of the American GRAS (Generally regarded as Safe) classification as a basis for a general guide to hazard would go a long way in alerting consumers to risks in their product choice. In the USA, substances and food additives are classified as GRAS where safety is generally recognised by qualified experts. i.e. they require both technical evidence of safety, and a basis to conclude that this technical evidence of safety is generally known and agreed by experts.  A GRAS classification would  give the unwary & ignorant an objective measure of hazard on which to base their options, should they wish to make enquiries. For example, in Australia, sassafras oil for internal use is not classified as a poison unless it contains a specified amount of safrole, in which case it is prohibited for internal therapeutic use. However, even without safrole the product is hazardous, as already stated. A consumer-friendly GRAS classification would alert people, whose children may be at risk, to the unknown hazards of accidental ingestion of substances not included in the GRAS list. Such people may then chose not to have such products at home. (The ingredients of dual-action Electric Blue Headlice Cream are GRAS.) 

12. Do we have to kill headlice to be rid of them?
No we don’t, if that is the answer you need for your ethics project! (But do read on!) Concerning headlice treatments, a State health department brochure says “If all lice are dead (no movement at all) the preparation has worked” This is rational ‘thinking within a box’. A more enlightened statement would be “If all lice are removed, the preparation has worked”. Death by an immediate toxic effect is an absolute measure of a product’s effectiveness, and is what most people want from pesticidal poisons. However, treatments that cause lice to stop feeding are potentially effective; this will cause death within a day or two. Or, a treatment that causes lice to lose their ability to claw-hold onto the hair shaft could also be effective. In this case, although alive, lice will be washed out on rinsing out the treatment with shampoo. (A product that stops lice breeding, or produces non-viable eggs, or repels them from the scalp would also be effective in the longer term). Bearing in mind that many people harbour head lice for weeks and months, products that work in non-conventional ways may be considered as rational alternatives.  Such products include oils of aniseed, cinnamon leaf and nutmeg. Electric Blue contains a combination of aromatic oils and works in several ways. It’s ultimate effect on headlice is demise by aromatherapy!

13. Why do some head lice treatments fail?
Problems in head lice eradication can occur for several reasons.

1) Not enough product and/or not enough time. Headlice products cannot work unless they come into contact with lice. No contact; No action! (And, if one pregnant female avoids contact, her eggs will develop into the next generation.) All hairs on the head should be covered with sufficient product to treat from roots to tips, particularly for long hair. To ensure proper coverage, comb it in with a normal comb (except for dreadlocks or tightly curled hair). The resulting detangled hair also facilitates fine-tooth combing at the end of the treatment. The product should remain in contact with the hair for about 30 minutes to ensure sufficient exposure.

2) Lice are resistant to the treatment. Head lice have become resistant to some insecticidal ingredients. Some lice are resistant to two ingredients simultaneously. Resistant lice look just the same as sensitive lice, and the best choice treatment will depend on resistance patterns in your area. If lice are moving at 4-8 hours after treatment, use a different insecticide class for a subsequent treatment. Resistance is more likely to occur with products such as malathion, pyrethrins, permethrin (& other synthetic pyrethroids) that leave a very small, non-fatal to lice, residue on the hair after washing. In the USA the CDC says "Treatment failures are common" with pyrethrins and permethrin. Malathion resistance is not a problem in the USA because, being restricted to prescription-only, head lice have not been widely exposed to it.

3) Failure to retreat to kill baby lice newly emerged from eggs. No matter what the product label says, NO product kills 100% of eggs. Eggs take 7-10 days to hatch. Therefore, starting from 1 day after treatment up to 7-10 days, nymphs (baby lice) may be emerging from eggs that survive the first treatment, or were not removed by fine-tooth combing. That's why re-treatment at 7-10 days is vital. If the treatment is effective, you would expect to find nymphs - but no adults - after the first treatment. The second treatment will mop up all remaining nymphs, well before they reach adulthood and reproduce.

4) Re-infection. Re-infection can give an impression that a treatment is not working. Don't forget that head lice can be 'caught' almost immediately after treatment if there is head-to-head contact with someone else who is already infected. (An exception is with oral medication that is not generally available.) Cross infection is likely if an adult louse is detected (with weekly detection combing) within a short time of a head being lice-free. Head lice is a 'communicable disease'. Therefore, to overcome constant re-infections, the challenge is to trace likely contacts, who should be checked for lice and treated if lousy.

5) Formulation and cosmetic elegance ("Yuk factor"). A product which is pleasant and easy-to-use is more likely to be used correctly than one which is not. For example, alcohol based products can cause problems such as stinging and burning, can trigger asthma and worsen eczema. Products with a low "yuk factor" are easier for children to accept on their heads for the full treatment time on both the first and follow-up application. (In the case of Electric Blue products, children approvingly report that it looks and smells like blue bubble gum.)

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