My cat had fleas a couple of months ago, and because I don't like using chemicals in general, I did some research on other ways of killing off fleas.
I ended up using something called Diatomaceous Earth (DE), which has been used for a long time in the food industry to kill off small bugs of all kinds. It's completely safe (as long as you don't breathe in the powder), and the way you use it is to
1. Rub the powder into the cat's fur, especially where the fleas are. My cat had them around the neck so I focused on that area but also covered the rest of the body.
2. Put the powder on the cat's bedding and any areas where they like to sleep/play etc. Leave on for as long as possible (I kept the powder on for about 6 hours, and I left the powder in his bed for four days). Then wash off the powder.
3. Sprinkle the powder on your mattress (under as well, if you have a mattress that comes off) - I just left this, it's still there
4. Add a large teaspoon of the powder to the cat's food every day, this helps prevent the fleas from coming back.
5. Comb the cats every day.
6. Add a little powder to the cat's fur every day, if necessary. I only did one 'whole body' application, and then one 'neck only' application a few days later.
After less than a week the fleas were gone, and they've not been back since. I still give him the powder in his food, but not every day. I'd say I'm now down to three times a week.
As a side effect, it also removed a stain that was on my mattress! And, it can also be used to treat worms in all animals.
I bought mine here:
Wiggly Wigglers, the really rural store