A common shampoo without anti-parasite substances doesn't help get a cat rid of fleas. (How to fight these parasites in another ways see below) The success of treatment depends both on processing of the animal and the surrounding furniture with insecticide chemicals. There are mach many fleas on the bedding than on a cat itself.
There are many kinds of shampoos today that contain insecticides. One may wash mature cats with them, but not kittens! After you wet the cat hair, rub the shampoo into fur intensively during 5 minutes; prevent it from getting it inside eyes and mouth. Wait the period of time pointed in a label (it depends on shampoo composition) and then douche the shampoo during 5 minutes till there's no any detergent on cat skin (otherwise shampoo will get into the cat stomach while it licks its' fur). Often it's useful to do the procedure described above before treating cat skin with an insecticide powder or aerosol.
There are firm kinds of soap containing insecticide substances but these are less convenient to use, moreover, the soap is more effective if not washed away from the fur, so there's a risk the cat will swallow insecticide. Anyway, firm soap is less effective than shampoo in flea control.
There's something more to explain. Washing (even with shampoo) doesn't guarantee that your cat will rid of fleas forever. Fleas may jump down during bathing and jump back after the end of procedure. Even if you have managed to do away with them there are too much insects around that are waiting for the opportunity to occupy the white space. Besides, fleas are very active and it is very difficult to get rid of them by simple brushing. Brushing may be useful for only one thing - detect the presence of fleas and their larvae.
Cat washing and treating of its' bedding with a disinfect solution doesn't deliver a cat from fleas. Disinfectants, in fact, don't mean this. Most flea eggs easily stand treatment of carpet and floor with insecticides. Disinfectants made of coniferous oil that are recommended for inside use (they may be on sale named differently) are relatively ineffective, and medical hygiene specialists don't take them seriously. Other antiseptics (remedies for skin disinfection) that are recommended to irrigate wounds are also not very effective for parasite control. These substances are unlikely to help you with flea control and will just frighten your cat by their smell, or will irritate skin, or cause alimentary disorder.
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).