actually they can be fatal - if you have a really bad problem with fleas on your young dog/cat they can die due to blood loss. Obviously they have to be really bad but i had a kitten in work once who had such a horrible flea problem that its pcv(red blood cell volume) was 3% - a normal pcv is like 35-40. it died on arrival
Flea shampoos dont work - what i do to control my fleas. is start with the capstar tabs to kill the fleas and then use a spot on treatment - advantage, frontline or revolution. I use revolution because it controls most intestinal worms to! If you are consistant with your flea treatment you dont even have to spend all those hours controlling the environment. Get it under control on your dog and you wont see another flea. I have three dogs and not one of them has a flea anymore and i have never washed their beds. Flea pupae (the stage between larvae and adult flea) and very resiliant, they have a little protective cocoon which is almost impossible to penetrate)
The malaseb, sebazole, pyohex are not flea shampoos - they are medicated shampoos for dogs/cats with skin problems, they wont kill fleas. The best form of treatment is a monthly spot on treatment.