Touching a cat's whiskers doesn't hurt, but pulling them does. The long, thick hairs that curve so gracefully from a cat's muzzle and above the eyes are not just decorations -- they're more like antennae or "feelers." They help the cat navigate, balance and keep out of trouble.
Look closely at a cat's face and you will probably see three horizontal lines of four whiskers each on either side of the nose; some cats have more than 24, but this is the average number. While the whiskers themselves are just hair, formed of keratin like your hair and fingernails, and have no feeling, they are connected under the skin to muscles that allow the cat to move them voluntarily and to nerves that register changes in the cat's environment and react to those changes. They also trigger involuntary reactions: touch your cat's whiskers on one side of his face and watch him wink at you -- just that fast, his whiskers told his brain to close his eye to protect it.
A cat can mobilize his whiskers at will. If he's hunting, he will point his whiskers as far forward as he can to detect any movement of his prey, to tell him when he's caught it and when it stops moving. Whiskers also give you a clue to a cat's mood -- if they're forward, he's feeling good, but if they're pasted back flat against his face, he's angry or afraid ... best leave him alone.
A cat's whiskers are almost a combination of radar and GPS -- they tell him where he is in space and what's around him. They're an important part of his sense of touch, and they contribute to his sense of balance. They tell him how big an opening is and whether he can get through it. They tell him about the weather and what's moving in his vicinity by reacting to variations in air flow. Even though he can see well in low light, in total darkness he can literally feel his way around obstacles.
If you suddenly lost your sense of touch, you'd have a hard time getting around, finding things and staying safe. If a cat loses his whiskers, he is likely to be slightly disoriented and will probably panic and hide or become frightened and aggressive in self-defense. Whiskers, like all other hairs, have a natural cycle and will fall out and grow back, but they do this individually in a pattern, so that the sensory function of the group is not disturbed. If all a cat's whiskers, or even most of them on one side, are damaged or cut, you may have a dizzy kitty for the two to three months it can take for them to grow back.