Can I bring reusable hand warmers onto a plane in Europe?

I'll be travelling from the UK to Hungary, and I was wondering whether I could bring two reusable hand warmers (the crystallisation type ones, like these) onto the plane, preferably as a cabin baggage. As they would be gifts, they are in their original packaging, but I'm not sure whether they would consider them fluids (I also don't know whether they are <100ml or not, they seem to be around the limit), or whether they would ban them outright, as they can activate accidentally therefore they might pose a fire risk.

I have found this TSA blog, they say it's okay, but that link is for US flights, and it also doesn't mention whether it would be considered fluid or not. I haven't found anything for EU flights.