Dr Margaret answers e-mailers' embarrassing problems in this biweekly problem page.

Scabies

Dear Dr Margaret
I’ve just had scabies (from I don’t know where). I had treatment about 2 weeks ago. The spots are almost gone, but the scabies nodules on my penis are still there and still itchy. They are not as bad as they were, but do I need more treatment?

If you used a good anti-scabies treatment, and you used it properly, you should be alright. The usual anti-scabies treatments are permethrin 5% cream, malathion 0.5% liquid or benzyl benzoate 25% emulsion. Scabies is caused by a tiny parasite that likes to live on human skin. All these treatments are fairly effective at killing the mites. Permethrin 5% cream is probably the best (about 90% success rate). Another treatment, lindane, is unavailable in the UK, so I am not familiar with it. The fact that you seem to be getting better suggests that the treatment has worked in your case, but here is some advice for anyone needing anti-scabies treatment.

It really is important to use these treatments exactly as the instructions tell you, otherwise they may not work. Benzyl benzoate has to be applied once a day for 3 days (i.e. three applications in all). Permethrin or malathion have to be applied twice, 1 week apart. You must apply the treatment to the whole of your body (except your head and face), even if only part of your body is itchy. Scabies mites often lurk under the nails, so use a cotton wool bud to put some treatment there. Before applying the treatment, cut your fingernails and toenails really short, and give them a good scrub to get rid of any dirt under the nail, because the mites could hide under the dirt and the treatment would not reach them.

Don’t have a hot bath just before applying the treatment, because the increased blood flow to the skin may carry the drug away from the skin too quickly. Don’t wash your body between treatments. You will probably need to wash your hands, so apply some more treatment to your hands afterwards. If you have a partner and/or family, they need treatment at the same time, even if they don’t have any itching or rash.

During the treatment, wash your bedlinen and clothes at 60° C.

The itching and other signs of scabies are actually an allergy to the saliva and faeces of the mite. After the mites are killed this allergy takes several weeks to go away. So it is normal to have itching or the rash for several weeks after successful treatment. But if the itching seems to be worsening you may need to use the treatment again, or to try another type. For more information about itching, look at our section on itching.

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