This is one nasty ‘trick’ this Halloween season…a new study has found that listeria may be harbored in a seasonal favorite.

Caramel apples with dipping stocks can lead to the growth of Listeria monocytogenes when stored at room temperature or even in the fridge.

The study tested caramel apples with and without dipping sticks and at different temperatures to see which conditions yielded the most growth.

After three days of observation and testing, the levels of listeria found on the room temperature apples with sticks increased 1,000 fold. By comparison, the growth of listeria on the refrigerated apples with sticks was significantly delayed.

Apples in the refrigerator with the stick showed no listeria growth for a week but then developed some growth over the next three weeks. The refrigerated caramel apples with no sticks showed no growth over four weeks.

Scientists describe that caramel has low water levels and apples are naturally acidic, two conditions which naturally would not make listeria growth likely. However, when the caramel apple is pierced with a stick, a little bit of juice leaks out and can be trapped underneath the caramel. This now creates the perfect breeding ground for listeria growth. This growth may start much more slowly when refrigerated, however, when kept at room temperature it will occur much faster.

Does this have to mean the end of your caramel-apple-loving days? Not necessarily. With this information in mind, you can take extra precautions (like refrigeration or eating apples fresh) to avoid contamination.