Scabies and head lice (Prescriber January 2011)

Guidelines for scabies treatment can be found here or here.  Some useful points, meanwhile:

  • Although manufacturers of scabicidal products only advise applying them from the neck downwards, the BNF actually advises applying them to the entire body, top to toe, including face, ears, scalp and neck. Then again, apparently the guidelines I’ve linked to above also advise applying from the neck down, so buggered if I know what we should be doing.
  • Benzyl benzoate is too irritant to use on children (and can be too irritant even on adults – some people have to wash it off within minutes due to the irritant effect).
  • The post-scabetic itch, which can take weeks to clear up, can be treated with emollients, mild/moderate topical steroids, crotamiton 10%, or a crotamiton/mild steroid combination (Eurax-HC).
  • Don’t forget oral ivermectin for Norwegian scabies, though it’s unlicenced.
  • For outbreaks in care homes, check the HPA guidelines above and consider the risk level for each staff member.

On to head lice:

  • They are only transferred by direct head-to-head contact and can’t jump from one head to another.
  • Nits can be seen in the hair after successful treatment and do not require further treatment in the absence of live lice (unless the treatment regime requires a second application to destroy newly-hatched lice).
  • Unlike scabies, lice does not require treatment of all family members – treat only those with visible lice in the hair.

Physical methods are usually the first port of call, as the lice can’t build up resistance to them the way they can to chemical methods.  Physical methods include dimethicone (in two different strengths), IPM/C (isopropylmyristate/cyclomethicone), and CAY (coconut, anise, and ylang ylang) spray.  All are applied to dry hair.  Do not use a hairdryer on them.

Dimethicone: The 4% strength is sold as Hedrin, and is the only method that’s cleared for use in pregnant/breastfeeding women and in children between 6 months and 2 years (and possibly <6 months on medical advice, although how I’m supposed to decide which under-6-month-olds can get it is not clear).  It’s left on for 8 hours, repeated 7 days later.

The 92% strength is sold as NYDA, and is also left on for 8 hours, but may not need to be repeated if there is no evidence of persisting head lice 8 – 10 days later.  It is not recommended in pregnancy, breastfeeding, or the under-2s, and the article is not clear on whether it’s OK in patients with asthma or eczema.

Both concentrations are flammable, so applying a naked flame to your hair is an even less good idea than it would usually be; on a more practical note, patients should not smoke while it’s on their hair, and should, presumably, beware of candles.

IPM/C: Sold as Full Marks (solution or spray).  This one only needs to be left on for 10 minutes, before being washed out using water and shampoo.  Repeat 7 days later.  (I can see that being considerably handier for disorganised people like us who never know what time in the evening the children are going to end up getting showered.)  It’s licenced for the over-2s and can be used in patients with asthma; the article claims it can also be used in patients with eczema but then states in the text that the NHS Clinical Knowledge Summary doesn’t recommend it for people with ‘skin conditions’.  No information is available on use in pregnancy or breastfeeding.

Coconut, anise, and ylang ylang spray: Sold, somewhat confusingly, as Lyclear Spray Away.  This one, again, only needs to be left on for 15 minutes before being washed out.  Repeat treatment 7 days later.  This one should not be used in people with skin conditions/broken or irritated skin, or with asthma.  There is no information on use in pregnancy or breastfeeding and it is not recommended for the under-2s.

If none of those suit, for whatever reason, then there are still the chemical treatments – malathion and permethrin.  Unfortunately resistance rates are very high.  Also, to complicate matters, the only form of permethrin that’s licenced for head lice is only supposed to be left on for ten minutes, which isn’t long enough to poison the lice.  On the plus side, malathion is considered safe in pregnancy and breastfeeding, so it could be another option for pregnant or breastfeeding women if Hedrin doesn’t work (unlikely to help, though, as Hedrin is about twice as effective).  Use the 0.5% aqueous solution of malathion, apply it to dry hair, and leave it on for 12 hours, repeating a week later.  You can use a third application if need be but don’t bother going for a fourth – if you haven’t cleared it up in three applications, repeated attempts just aren’t going to be helpful.

For people who dislike any mention of chemicals, there’s always wet combing – otherwise known as bug busting, it’s the process of combing wet hair with a fine-toothed comb to get rid of the lice as they hatch.  However, it’s time-consuming – you have to do it every four days for at least two weeks or until you have seen no lice on three consecutive combing sessions, whichever comes second – and failure rates are high (studies have shown between 38 and 57% cure at 14 days).


About Dr Sarah

I'm a GP with a husband and two young children.
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