You can void your warranty if water or other liquids gets into the headphone jack of your mobile.
Most smart phones have a sensor inside which turns red when it comes in contact with liquids. This can cause the phone to malfunction, which can be annoying, frustrating, time consuming and potentially costly!
Refer to Apple's website for warranty terms and conditions.
Also refer to the below link which high-light the potential problems.
Promote longevity of your device by purchasing an iCatchi Plug which is inexpensive when compared to the cost of your smartphone, game or iPad.
Think of it as an insurance policy for your phone!