Organic tick repellents differ widely in efficacy, study shows

By Mariam Sunny

(Reuters) – Increasingly popular botanical oils for repelling and killing ticks are not always as effective as regulated chemical products, according to a report published on Wednesday by the U.S. Centers for Disease Control and Prevention (CDC).

Some of these unregulated products have only minimal impact on ticks, a review of existing research found.

Different products with the same active ingredients showed “highly variable” efficacy against black-legged ticks that transmit bacteria causing Lyme disease, Babesiosis, Ehrlichiosis, and other infections, the study found.

Most research has consisted of field studies involving wild ticks on vegetation.

When Sandoz (SIX:) products Eco-Exempt IC2 and Essentria IC3, both containing rosemary oil and peppermint oil as active ingredients, were evaluated in field trials, the former showed 87% suppression of ticks while the latter showed only up to 53% suppression, the study found.

In a separate field test, Eco-Exempt IC2 was as effective as an Environmental Protection Agency-approved (EPA) synthetic chemical product for several months after application.

Little is known about the effectiveness of oil-based products when applied to skin, the study found.

Oil-based tick repellents, called minimum risk products, are not regulated by the EPA as they are considered safe for people and the environment.

“More work needs to be done to better understand the effectiveness of minimum risk products,” said Lars Eisen, the CDC researcher who conducted the analysis published in the Emerging Infectious Diseases journal.

Active ingredients allowable in minimum risk products include spices such as cinnamon, citronella, and rosemary, and botanical oils such as castor oil, clove oil and lemongrass oil.

EPA-registered synthetic pesticides were more stable in the environment and highly effective in suppressing the disease carrying ticks for longer periods compared to oil-based products, the report said.

Pesticides based on cedarwood oil are commonly offered by commercial firms providing tick control services in the northeastern United States. Tests of two such products found neither provided more than minimal tick control, the report said.

Use of EPA-registered products is recommended by public health agencies, but consumers may choose organic tick repellents believing them to be safer, the report said.

“Independent sources of information on the effectiveness of specific products are often lacking,” Eisen said.