Thank you all for the very helpful replies and sorry for delay in coming back on here again - 5 people fighting over sharing one laptop here.
bochead - thanks for tips re supplements, I will investigate the magnesium and zinc supplements. Unfortunately epsom salts in bath is probably a no no at the moment as she says even plain water stings.
oodlesofdoodles - we have tried exclusion diets as she tested as allergic to long list of foodstuffs, but with no particular improvement in her skin.Suspect the food allergies are just part of the cause.
frizzcat - thanks for the tip re detoxpeople spray.
debs75 - from your description of the benefits for your son, it sounds like ther would be times when it would help dd's older brother too (also a very grumpy asd teenager). He is very hard to get off to sleep but thankfully normally stays asleep unless he's having a major stress about something.
grumpypants - I can understand you being put off by GP's warning. I think I will have to do some more googling to see what info is out there about potential side-effects
hyperotreti , cansu, intothewest, lovely boys - good to hear that it is effective - at least with the getting off to sleep for your dcs
zzzz - interesting that it seems to be less restricted in mainland Europe than here
fanjo - getting the right medication does seem to be all about trial and error, many anti-histamines that would knock out most adults seem to have no effect on dd whatsoever.
I think I will try to find out more about any potential medical contra-indications/risks vs benefits and then if it sounds like it is appropriate for her I will raise it with the consulatnt next time we see her.
Thanks again for taking the time to reply.