My daughter was 7 when she contracted chicken pox. The itchiness was preventing her from sleeping, so I made up a solution of pure peppermint oil & water. (You can also use pure lavender oil). To 1 litre of water add 1 drop. Shake vigorously, tip out half the water, top up with water to again make 1 litre and then do it again, so you end up with 1/4 oil to 1 litre of water. This works on the homeopathic principle of attenuation (to weaken/reduce in intensity). I applied it where-ever the spots were, and within minutes the itching had stopped, and she was able to sleep peacefully. I prefer peppermint oil, as it has a soothing & cooling effect, and the spots clear up quickly with no scarring.
Have respect when using this oil, (as it is very potent) and be careful not to get any near your eyes or face, as it burns! (I can tell you this from personal experience!) Flush with plenty of water should this happen. However, reduced down to a quarter of its strength, it makes a formidable ally against chicken pox itching and scratching!