Tests have shown that Brewer's yeast does not protect pets from fleas. The pet's living areas should be treated at the same time that the pet is treated. This kills immature and newly emerging fleas and prevents re-infestation of the pet. Several low-toxicity treatments are available for indoor use. These products kill fleas on contact, but evaporate quickly and leave little residual protection against emerging fleas.
Borates kill immature fleas by contaminating their food supply.
Because adult fleas feed on fresh blood only, boron insecticides do not control this life stage. Borate treatments are best applied as shampoos to avoid problems with dustiness, abrasion to carpets, and contamination of furniture or food preparation surfaces. Outdoors treat only flea breeding sites such as bedding areas, the ground under decks and shrubbery, and wherever pets spend a lot of time. Well maintained lawns in sunny sites are unlikely to harbor many fleas. Because flea pupae are hard to kill with insecticides, an additional followup treatment is usually needed 7 to 10 days after the first application.