Hope this might be of use to someone. Last week I started adding Grapefruit Seed Extract (which apparently has brilliant anti viral properties) and Tea Tree Oil to DD's baths and have also made up a mixture of the two in a base of olive oil that I have been putting directly onto them every night (using new cotton wool balls for each area to try and prevent it spreading).
I can honestly say within a day or two I could see a noticeable difference and a week on they have changed massively. They have shrunk right down, gone much flatter and look less sore (a few stubborn ones on her arms aren't responding as quickly as those on her torso). I think it must be to do with what I've been putting on rather than them reaching the end of their life cycle as most of them were relatively new ones.
Just a word of caution the Grapefruit Seed Extract is very strong and can be an irritant to the skin so if anyone does try it please make sure it is diluted and only use a tiny bit first in case of any reaction to it.
I am going to persevere with this and will keep you posted! HTH