It's disgusting when your cat is infested with fleas. Even worse though, is that fleas carry a variety of illnesses that can affect you and your cat. Sometimes an extreme treatment like dunking your cat in flea dip is necessary to get rid of the pests.
Why?
A flea dip is a pretty harsh treatment if you're a cat. Not only will your cat probably resent being dunked in liquid, but toxins in a flea dip can be hard for your kitty's body to process. Even dips designed specifically for cats use dangerous chemicals. Before dipping your cat, decide whether it's the best treatment. If your cat has a severe infestation and waiting for other types of treatments to take effect is not an option, then a flea dip might be the right thing. However, if it's a small infestation and you have the liberty of waiting a few hours or days for the treatment to do its job, then a different type of flea treatment is probably a lot safer and less stressful for your cat.
Effectiveness
Flea dips are generally pretty effective -- as long as you can get your cat completely dipped. When done right, the dip will kill any adult fleas on your cat. Some dips will repel fleas as well. The dip may not necessarily kill the flea eggs, and another treatment may be necessary to get rid of the problem. Also, as your cat grooms himself and his natural oils take back over, any repellent will be reduced.
Safety
The biggest issue with giving a cat a flea dip is safety. Not the safety of the humans involved -- although that could also be a problem -- the safety of the chemicals being used on the cat. Flea dips designed for dogs can kill a cat. A cat's body cannot process the chemicals the way a dog does, and the result is a poisoned kitty. Never use a flea dip that is marked only for dogs. Be sure the dip is intended for use on cats. Also, if you intend to dip a young kitten, check the label to see if it's safe for young kittens or only for adult cats. Follow the manufacturer's instructions exactly so that you don't accidentally poison your cat. Cats with health problems or that are very skinny should not be dipped, even in solutions designed for cats. Your cat should be healthy before getting a flea dip.
Dipping a Cat
Health concerns aside, dipping a cat for fleas can be tricky. Very few cats will simply let you pick them up and put them in a sink full of water. You'll want to have the dip solution already prepared and a few towels nearby. An assistant will probably be necessary too. With one hand, hold your cat's front paws together while supporting his body weight. The other hand should have a firm grip on the scruff on the back of his neck, but don't use the scruff to support his body weight. Your assistant should hold your cat's back legs together. Lower your cat into the dip and hold him there as long as recommended by the directions. You may also need to have the assistant wipe his face with a washcloth soaked in the dip. Be careful not to get the flea dip into his eyes or ears. When the time is up, lift your kitty out of the dip and wrap him in a dry towel.
Alternatives
There are a lot of effective alternatives to dipping your cat. Spot treatments both control and repel fleas and are simple to apply to your cat's fur. Just like with dips, make sure the product is meant for cats and not for dogs. You can also use a fine tooth flea comb to remove fleas manually.