Almost nightly, I suffer several very disturbing hours before falling into an exhausted sleep as a result of spasmodic twitching in either one of my legs. Various doctors have diagnosed this as restless legs but none has been able to explain the cause, or offer a remedy. Can you?

You seem to have classic 'restless legs'. These are muscle twitches that occur just before you drop off to sleep. We aren't sure of the cause, but it may be a nerve irritation or linked to local circulation problems in the legs. Either way, the general advice is to eat earlier in the evening, don't drink alcohol in the evening and don't smoke at all. Two prescription medicines are licensed to treat restless legs - pramipexole (Mirapexin) and ropinirole (Adartrel). There is an International Restless Legs score, believe it or not, and you may be advised to take one of these drugs if your score is 24 or more. Talk to your doctor again about them.

How long are children infectious with chickenpox? And when can they go back to school?

They can spread the disease from two days before the rash appears (when they feel a bit ropey but no one yet knows the diagnosis) until around five days after the rash has appeared. Children can return to school or nursery after the spots have dried and crusted. That's usually around six days after the start of the rash, but can be longer. Tell friends who may be in very early pregnancy not to visit, as chickenpox can harm a developing foetus.

· Do you have a question for Dr Smith? Email doctordoctor@theguardian.com