Aren’t rubber hot-water bottles just made of rubber? Yes, some are, but others use thermoplastic instead.
Two important factors to note concerning rubber hot-water bottles are: Rubber hot-water bottles are thicker than plastic — and thus take longer for the heat to make its way through — and people with latex allergies should avoid rubber hot-water bottles entirely.
Thermoplastic bottles have a few pros and cons compared to rubber. They’re usually thinner and slightly transparent, which can make it easier to see the water level and for heat to transfer faster, but they also increase the chances of leaks, ruptures and tears. Thermoplastic is also safe for those with latex allergies to use.