I came across a website called hairnailskincare.com just after my last post, and they were suggesting that users were experiencing reactions to bismuth oxychloride. They thought that this was due to chemical sensitivity – but I think this is unlikely.
I tried to post this reply but their comments feature wasn’t working correctly. I will leave it up here until I hear back from them.
I don’t think it is at all likely that bismuth oxychloride would react chemically with the skin. It is much more likely that any reactions are simply down to the particle size and shape. It probably isn’t going to help very much looking at the chemical names on the pack because different grades of the same material might well be very different. Look at the difference between icing sugar and granulated sugar. Both are exactly the same chemical but they behave very differently. Its unfortunate, but there isn’t really any substitute for trying things out and seeing if they work for you or not.