Adrian Kingsley-Hughes/ZDNET
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ZDNET's key takeaways
Lithium button cells can cause severe injury or death if swallowed.
Many makers coat their batteries in a bitter substance to discourage ingestion.
Energizer has now added a marker dye to make it easier to spot ingestion.
Lithium button cell (sometimes called coin cell) batteries are everywhere, from car key fobs to AirTags. And while they seem innocent enough, if ingested, they can cause severe injury from esophageal or airway damage in less than two hours, which can, in the worst cases, result in death.
Each year in the US alone, some 3,500 button cells are swallowed, mostly by children. I've encountered one such injury myself, and seen a number of examples in first aid training materials, and it is no joke.
Making button cells safer requires two things: preventing accidental ingestion and being able to spot if a button cell has been ingested.
Also: The best rechargeable batteries you can buy
For a few years now, several button cell manufacturers have been coating their batteries in Bitrex, a harmless chemical compound that's the most bitter substance known. A thimbleful in an Olympic-sized swimming pool can make all the water bitter.
This substance is added to a wide array of products to prevent ingestion, from bleach and antifreeze to Nintendo game cards. And let me tell you, this stuff is awful (if you don't believe me, you can actually request a free taste test kit from the maker).
Another step that manufacturers have taken is to make the packaging hard to open without using scissors. This makes it much harder for adults and children alike to access new batteries.
Getting into the packaging is the first hurdle that toddlers have to cross. Adrian Kingsley-Hughes/ZDNET
It's not even easy with scissors! Adrian Kingsley-Hughes/ZDNET
Battery maker Energizer has taken things a step further with its Color Alert line. In addition to hard-to-open packaging and a liberal application of Bitrex, a patch of dye has been applied to the battery to make it more obvious if it has been in someone's mouth. The Color Alert line covers common button cell sizes such as CR2032, CR2025, and CR2016.
The food-grade dye is applied in dots to the back of the battery. It doesn't look like much, but it's more than enough!
These dots are the dye. Adrian Kingsley-Hughes/ZDNET
Once this comes into contact with water or saliva, it dissolves and spreads rapidly, going everywhere. The bright blue really shows up against skin, especially in the mouth and on the tongue.
Release the dye! Adrian Kingsley-Hughes/ZDNET
The dye stains skin for many hours (in my tests, it stayed on my skin for many hours, resisting several attempts to wash it off), and can alert caregivers to the fact that a button cell may have been ingested.
The dye gets everywhere and is very persistent! Adrian Kingsley-Hughes/ZDNET
Oh yes, and don't forget about the Bitrex in the dye. I taste-tested it and regretted it!
Yes, there's Bitrex in the dye. Here I applied a small dot of the dye to my tongue and regretted it! Adrian Kingsley-Hughes/ZDNET
If you suspect that a button cell has been ingested, go immediately to the emergency room.
If you are unsure, call Poison Control immediately on 1-800-222-1222.
The dye and Bitrex coating seem to have no effect on the usability of the batteries. There was an issue with some Duracell cells being problematic in some devices -- notably AirTags -- but I've not had any similar issues with the Energizer cells.
These are the safest button cells I've used, and as such, I recommend that you buy only them. They keep you safe (not that most of my readers are going to eat batteries), keep children and vulnerable people around you safe, and also help to keep pets safe (yeah, some of them will eat coin cells, too).
I've had no problem with Energizer batteries -- I also use the lithium AA and AAA batteries where I need long life or resistance to cold temperatures -- and prices are reasonable. A six-pack of CR2032, the most commonly used size, and the one that fits into AirTags, is only $7.