Not all PCM's are created equal. ThermApparel’s PCM is USDA-certified non-toxic and biodegradable. We chose it because it outperforms paraffin, salt hydrates, gel, and ice in several areas such as long-term stability, sustainable materials, safety on the skin, and zero dangerous oils or hard-to-clean waxes. Our lightweight and flexible PCM Cooling Packs are reusable, making them able to be recharged over and over again. Read more info about PCM and see our safety data sheet for more info.