A foaming or hissing watermelon can be alarming, and for good reason. When a watermelon begins to ferment, pressure builds up inside the fruit, and in some cases it can burst unexpectedly. Fermentation can happen when bacteria enter small cracks in the rind, when the fruit is overripe, or when it was damaged during transport or storage. If you ever notice foaming, bulging, leaking, or a sour smell, it’s important to handle the melon carefully and remove it from your home.
Fermenting watermelons create internal gas that can cause the fruit to swell and eventually explode. This is why experts recommend moving the watermelon outside or into a safe, open area as soon as you notice unusual activity. Do not cut into it, squeeze it, or try to “check the inside.” Even slight pressure can trigger it to split unexpectedly. The safest option is to place it inside a garbage bag, tie it securely, and carry it outdoors. Avoid placing your face or hands directly over the melon while handling it.
Once the watermelon is outside, dispose of it in a trash bin or designated waste area. If it later explodes, it may create a mess, attract insects, or damage the container, but at least the risk is no longer inside your home. This is especially important during warm weather, when fermentation happens more quickly and pests can spread rapidly. If the explosion leaves behind residue or insects, clean the area with hot soapy water or disinfectant to remove bacteria and odors.
To prevent this from happening in the future, always inspect watermelons before buying. Avoid melons with soft spots, dents, cracks, or leaking areas. A fresh, healthy watermelon should feel firm and heavy for its size, with a symmetrical shape and no signs of damage. Store whole watermelons in a cool place and refrigerate them once cut. If you notice any bubbling, foaming, strange smells, or pressure buildup, treat the melon as unsafe and handle it with caution.
Fermenting watermelons are unusual but not rare, especially during hot seasons or when the fruit has been mishandled. By recognizing the signs early and knowing how to dispose of them safely, you can protect your home and avoid a messy—and potentially dangerous—surprise.
