What causes a battery to leak?
When a (alkaline) battery is charged, the chemicals inside produce a gas. If this happens too frequently, the battery cell may rupture. This is where leakage could happen. The battery seal normally prevents this.
What's the issue with that? Should a battery be able to withstand this kind of stress? Both yes and no. A battery should not leak after normal use. The cell is strong enough to withstand the accumulation of gasses inside.
Leakage occurs when a battery is left in a device for an extended period of time, particularly when the device is not in use. Even when that device is turned off, it continues to 'check' for remaining power. This places some strain on the battery, increasing the likelihood of leakage.
How to prevent a battery leak?
If you are not going to use your device for an extended period of time, remove the batteries to prevent them from leaking.
In addition, when inserting multiple batteries into a device, always use the same brand, type, and energy level. Why? When you mix batteries, you create an imbalance: the 'stronger' a battery will overcompensate and discharge too quickly, putting it at risk of leakage.
What to do with leaking batteries?
What should you do if you discover a battery leak? Remove the battery right away, but use caution: work in a well-ventilated area away from heat sources. To avoid contact with the residue, wear protective eyewear and gloves if possible. After removing the leaking batteries, use a cotton swab or an old toothbrush to clean out the battery compartment. Recycle the batteries by placing them in a plastic bag.
At all times, avoid coming into contact with the discharge. After using soap and water, always thoroughly wash your hands. Seek medical attention immediately if you make eye contact.