Button batteries are small, round, single-cell batteries shaped like a button or coin. They power everyday devices from watches to hearing aids, and they come in sizes ranging from about 5mm to over 25mm in diameter. While convenient and widely used, they pose serious safety risks if swallowed, particularly by young children.
How Button Batteries Are Named and Sized
Every button battery has an alphanumeric code printed on it, and that code tells you everything about its chemistry and dimensions. The first one or two letters indicate the type of battery chemistry inside:
- CR: Lithium, producing 3 volts
- LR: Alkaline, producing 1.5 volts
- SR: Silver oxide, producing 1.55 volts
The numbers after the letters describe the physical size. The first two digits represent the diameter in millimeters, and the last two digits represent the thickness in tenths of a millimeter. A CR2032, one of the most common button batteries, is 20mm across and 3.2mm thick. An LR44 is 11.6mm across and 5.4mm thick. Once you understand the code, you can decode any button battery at a glance.
Lithium coin cells (CR types) are the largest and most powerful of the group. They’re also the most dangerous if swallowed, because their higher voltage causes tissue damage faster.
Where You’ll Find Them at Home
Button batteries are in far more household items than most people realize. The obvious ones include watches, hearing aids, and calculators. But they also sit inside car key fobs, digital thermometers, kitchen and bathroom scales, remote controls for TVs and garage doors, and small cameras.
Less obvious sources include musical greeting cards, children’s talking books, keychain flashlights, novelty items, light-up clothing and jewelry, and imitation candles. Many of these products have battery compartments that aren’t secured with screws, making it easy for a child to pop out a battery. After the holidays, greeting cards with embedded batteries are a particularly overlooked hazard.
Why Swallowed Button Batteries Are Dangerous
A swallowed button battery can cause severe internal burns in a remarkably short time. The primary damage doesn’t come from the battery leaking its contents. Instead, it comes from an electrical reaction between the battery and the moist tissue it’s resting against.
When a button battery lodges in the esophagus (the tube between the mouth and stomach), it generates a small electrical current that splits water molecules in the surrounding tissue. This process, called electrolysis, produces hydroxide ions at the battery’s negative pole. The tissue around that pole becomes extremely alkaline, reaching a pH of 11 within just 30 seconds. For reference, household bleach sits around pH 12.
Alkaline burns are particularly destructive because they don’t stop at the surface. Unlike acid burns, which form a barrier of damaged tissue that limits further penetration, alkaline substances dissolve proteins and fats progressively deeper into the tissue. In animal studies, necrosis extended into the outer muscle layers of the esophagus within just 15 to 30 minutes, even though the batteries hadn’t leaked at all. Visible ulceration appeared by four hours. The batteries didn’t actually leak their internal contents until they’d been lodged for more than 48 hours, confirming that the electrical burn, not chemical leakage, is the real threat.
Signs a Child May Have Swallowed One
Young children often swallow button batteries without anyone seeing it happen, which makes recognizing the symptoms critical. Common signs include coughing, drooling, difficulty swallowing, refusal to eat, irritability, vomiting, and fever. If a battery lodges higher in the esophagus, which is more common in younger children, breathing difficulties are more likely. Older children with mid-to-lower esophageal lodging tend to report pain along with feeding and breathing trouble.
Button batteries can also end up in the nose or ears. A battery stuck in the nasal cavity may cause nasal discharge, facial swelling, or swelling around the eyes. One lodged in the ear canal can produce a foul-smelling discharge if infection develops.
If you suspect a child has swallowed a button battery, the situation is a medical emergency. X-rays can confirm the location: button batteries show a distinctive double-ring or “halo” appearance on imaging that distinguishes them from coins.
Honey as a First Response
For children over one year old, giving small amounts of honey on the way to the emergency room may help slow tissue damage. Honey coats the battery and the surrounding tissue, creating a temporary barrier that reduces the severity of the alkaline burn. This approach has been endorsed by the National Capital Poison Center in the U.S. and by European pediatric gastroenterology guidelines. It’s not a substitute for emergency removal, but it can buy time during transport. Honey should not be given to children under one year old due to the risk of infant botulism.
U.S. Safety Regulations
In 2022, Congress passed Reese’s Law, named after an 18-month-old who died after swallowing a button battery from a remote control. The law requires that battery compartments on consumer products be secured so they need either a tool (like a small screwdriver) or two simultaneous hand movements to open. Products must also pass abuse testing to ensure batteries can’t come loose from impacts or rough handling. Warning labels are required on product packaging, on the product itself when practical, and in any included manuals or instructions.
Safe Storage and Disposal
Keep spare button batteries in their original packaging and store them out of reach of children, ideally in a locked or high cabinet. When you remove a used battery from a device, don’t leave it sitting on a counter or toss it loosely in a drawer.
For disposal, tape the terminals of used button batteries with clear packing tape before recycling or discarding them. This prevents the battery from creating a spark if it contacts other batteries or metal objects, which can start a fire. Only tape the terminals, not the entire battery, so waste handlers can identify the battery type. Alternatively, place each used battery in its own small, clear sealable bag. Any battery that shows signs of leakage or damage should go straight into a sealed bag.
Lithium (CR) and silver oxide (SR) button batteries contain heavy metals and should be recycled rather than thrown in the trash. Many electronics retailers have free drop-off kiosks near their entrance. Alkaline (LR) button batteries can generally go in household trash, though recycling is still the better option where available.