Question about thermal heat patches

All right, I was using one of those “thermal heat patches” to help with my cramps. On the package, it says you can discard when cool, and as it wasn’t quite cool, I wet it. Curious as to what was inside, I cut it, and there was this black dirt like substance.

I threw it away and washed my hands.

Now, I just read the package again and it says:

Am I going to get some hideous rash? Or worse-iron poisoning?

Please help this stupid hypochondriac!


The black dirtlike stuff was very finely divided iron filings. They rust (oxidize) when exposed to air and give off heat. If you had opened the package before the iron was mostly oxidized, you could have gotten the stuff on your skin, where it would give off heat, and possibly burn you. Once the iron is oxidized, its no more dangerous than the scrapings from a rusty tailpipe. It can be pretty messy though !