Boiled eggs are a summer lifesaver - quick protein for a salad, a snack or breakfast. But it's precisely in high temperatures that they also become a potential hazard if stored wrong, and the mistake almost everyone makes is simple: leaving them out of the fridge for too long.

The rule is clear. A boiled egg must not sit at room temperature for more than two hours. When the thermometer goes past 30 degrees, that window shrinks even further. As soon as the egg has cooled a little after boiling, it goes into the fridge - and not in the door, but inside, away from the frequent temperature changes every time it's opened.

There are a few more rules that cost nothing and save your stomach. Don't leave eggs in the car or in direct sun after shopping. Don't wash them before storing - the natural coating of the shell is a protection against bacteria. Cool the boiled ones and put them in the fridge straight away. And always check the shells for cracks or damage.

And if you're not sure whether an egg is still fresh, there's an old, foolproof test: drop it into cold water. If it lies flat on the bottom - it's fresh. If it floats or stands upright - throw it out. The air pocket inside has grown, which means the egg has lost its freshness. Simple, free and faster than any date on the shell.