[ghporter]

Without going into too much detail for background, it’s pool season so it’s time to mix a batch of “ear drying drops” to ward off swimmer’s ear. This is half 70% isopropyl alcohol and half 5% vinegar. The vinegar acidifies the ear canal to kill bacteria, and the alcohol dissolves any water, allowing it to either quickly evaporate or drip out with the head tilted.

But there’s another DIY ear drop for addressing stubborn ear wax, made of half 70% alcohol and half 3% hydrogen peroxide. Again, the alcohol helps keep the drops from staying around for too long, and the peroxide works to break up the wax.

Here’s where I’m going: supposedly making an “combination ear drying and ear wax drop” with the above components is Very Very Bad. The acetic acid and the hydrogen peroxide react to produce paracetic (or peroxyacetic) acid.

Internet randos have posted horror stories about the dangers of paracetic acid which “in its concentrated form it is highly corrosive and unstable” (per the USDA) (emphasis mine).

But…. (Here’s the chemistry part.) If I put 10ml of 5% acetic solution in a container with 10ml of 3% hydrogen peroxide solution, that’s 19.2ml of water and 0.8ml of “reactants”. Just how dangerous/unstable/corrosive is 0.8ml of paracetic (peroxyacetic) acid in 19.2ml of water?

[reader50]

I buy off-the-shelf earwax removal drops, rather than test home chemistry. They're labeled as "carbamide peroxide 6.5%".

It's been a long time since chem class. But testing how strong an acid is, by dripping it into one ear is definitely the way to go. If it's too strong, you always have the spare ear.