Apple unveiled the iPhone 5S at a press event at its Cupertino Calif. headquarters on Tuesday. One of the biggest new features the company showcased was the smartphone's new Touch ID fingerprint scanner. While the idea seems good in theory, in practice, even Apple has admitted that the Touch ID scanner isn't perfect and doesn't like sweaty fingers.

An Apple spokesperson told the Wall Street Journal that the phone doesn't always work with moisture-laden fingers. In other words, people whose fingers are covered in sweat, lotion or other liquids will give the Touch ID difficulty in unlocking the device until such substances are wiped clear. In other words, if you're prone to sweaty hands or are a fan of keeping your hands and fingers moisturized with lotion, Apple's newest security features might not be for you.

An Apple spokesperson did point out that the other security features on the iPhone are enough to keep the device safe if Touch ID doesn't sound right for you. In fact, the phone will require users who want to use Touch ID to create a passcode as a backup. Only the passcode (not a finger) can unloick the phone if the phone has been rebooted or hasn't been unlocked in 48 hours. This feature is meant to block hackers from stalling for time as they try to find a way to circumvent the fingerprint scanner.

The device will also have some difficulty reading some fingers, particularly those with scars on them by accidents or surgery. Of course, in those cases the users can simply use another finger to scan on the device instead.

Apple called the iPhone 5S one of the most secure smartphones on the market as a result of the fingerprint scanner. However, problems with the technology are likely to crop up. Users won't know until the phone hits shelves on Sept. 20 if the functionality is really worth it. It remains to be seen if the phone will keep unwanted visitors out or if it will keep users out instead.