Before you panic, take a look. Half the time it's not a leak — it's condensation. When warm vapor hits the cooler mouthpiece, it turns back into liquid. Wipe the mouthpiece and the air holes with a dry cloth. If the liquid is clear and thin, it's condensation. If it's sticky and sweet, that's e-liquid.

Another common cause is temperature change. If you went from a warm car to the cold outdoors, the juice thins and expands. Let the device sit upright for 15 minutes so excess liquid can settle back into the wick.