Dog Health by LowchensAustralia.com

Natural Flea Control Products

Pyrethrins are insecticides derived from the chrysanthemum plant. They are common ingredients of flea control products and have excellent "knockdown" properties against fleas. They are neurotoxic at high levels, and may cause excessive salivation, vomiting, difficulty breathing, muscle tremors, depression, and ataxia (wobbling). Cats may develop excessive salivation, contractions of superficial muscles (ear flicking, paw shaking) or the signs mentioned above. However, the products are considered fairly safe when applied properly. Apply sparingly.
Reference: Hansen SR, Stemme KA, Villar D, et al. Pyrethrins and Pyrethroids in dogs and cats. Comp Cont Ed Pract Vet 16:707-712, 1994.

Rotenone is an insecticide derived from the root of Derris ellipta. It is used in shampoos, sprays, and rinses. Rotenone is quite toxic to fish and small mammals (e.g., guinea pigs), therefore caution should be exercised when applying this agent around those animals. The compound rapidly decomposes upon exposure to light and air, however ingestion by dogs or cats may result in vomiting.

Citrus fruit derivatives: D-limonene is the most commonly used derivative of citrus fruits. This substance is a volatile oil that has moderately good knockdown properties, but is fairly mild. The main advantage of this product is a high margin of safety, making it a good product for application on kittens and puppies, as well as in households with infants. Citrus derivatives are available as shampoos and rinses.
Reference: Hooser SB, et al. Effects of an insecticidal dip containing d-limonene in the cat. J Am Vet Med Assoc 189:905-908, 1986.

Thiamine (Vitamin B1) has been often discussed, but has not been shown to be an effective flea control agent when administered orally. I'm sure some people will disagree but the scientific evidence suggests there is little value in giving your pet thiamine for flea repellent effects. 
Reference: Halliwell REW. Ineffectiveness of thiamine (vitamin B1) as a flea repellent in dogs. J Am Animl Hosp Assoc 18:423-426, 1982.

Avon's Skin-So-Soft®: Skin-So-Soft has been shown to partially repel fleas when topically applied at a concentration of 1.5 ounces of SSS per gallon of water. The repellent effect is not complete, but significantly fewer fleas were found on dogs treated with SSS vs. water in one controlled study. The effects seem to last at least 8 days. No toxic effects of the treatment were observed in the study, however long-term effects have not been studied.
Reference: Fehrer SL, et al. Effectiveness of Avon's Skin-So-Soft as a flea repellent on dogs. J Am Anim Hosp Assoc 23:217-220, 1987.

Melaleuca oil is derived from the Australian tea-tree, Melaleuca alternifolia. It does have antibacterial and antifungal properties and has been used for those purposes topically on dogs and cats. Inappropriate application of products not intended for topical use may result in toxicity, with animals showing signs of incoordination, weakness, tremors, and depression. The efficacy of this agent to repel or kill fleas has not been established at this time.
Reference: Nicholson SS. Toxicity of insecticides and skin care products of botanical origin. Vet Dermatology 1995:6;139-142.

Garlic has not been shown to consistently repel fleas (despite the evidence that garlic has many beneficial effects in humans). 

Cedar chips or wood may have some repellent properties, however my personal experiences suggest it is nether complete nor consistent.

Pennyroyal oil is derived from the leaves and flowers of the pennyroyal, squaw mint, or mosquito plants. Pennyroyal oil contains a volatile compound called pulegone, which is responsible for the toxic effects of the plants. Historically, the plant has been used as an abortifacient in folklore medicine and is used as a component of fragrances. The product is used for flea control and is available in flea shampoos, powders, and as pennyroyal oil. The effectiveness of the compound is unclear, however the toxicity is clear. Exposure to pennyroyal oil may induce depression, vomiting, hepatic necrosis, diarrhea, epistaxis (nose bleeds), seizures, and death. Toxicity is dose-related and the possibility of severe signs is more likely if the pure oil is applied to the pet.
Reference: Sudekum M, et al. Pennyroyal oil toxicosis in a dog. J Am Vet Med Assoc 200:817-818, 1992.

Diatomaceous earth: Diatomaceous earth is a dessicant (drying agent) (See Treatment of the House) and also works as a chaffing agent to fleas. It may be spread in an environment to help reduce the humidity in carpet. Diatomaceous earth is available at stores catering to health or natural foods/products. Its effectiveness is variable. The product may be toxic to humans, since it contains a significant percentage of silica, and silica can cause lung disease in humans if inhaled. An alternative to the application of diatomaceous earth is the application of the borates.

Biologic control using the nematode Steinernema carpocapsa is based on the fact that these nematodes parasitize the flea (and other insects) larvae and result in their destruction. The nematodes are applied as a spray to the ground. Application of the nematodes must be periodically repeated. This product is best suited for situations where the pet spends a high percentage of time outdoors and the product is applied to shaded areas. The full effects of this treatment on other insects (both beneficial and harmful) are unknown. This form of treatment would only be one part of a larger flea control program.
Reference: Smith CA. Searching for safe methods of flea control. J Am Vet Med Assoc 206:1137-1143, 1995. 

See our page on Diatomaceous earth