Important Note: the following article compares DEET with Permethrin as a tick repellent for humans. While Permethrin is fairly safe to humans when used properly, it is very toxic to cats, fish and aquatic life in general! More information is provided below, under the heading "Additional information about DEET and Permethrin".

DEET versus Permethrin as a Tick Repellent

By Tom Grier

Springtime is tick time. This means we will soon be seeing those cautionary ads on television telling us to use tick repellents. In almost every instance, the active ingredient in those advertised tick repellents will be DEET, which is the active ingredient in most mosquito repellents.

DEET is an excellent mosquito repellent, but it is a fairly poor tick repellent. We are inundated with so many DEET repellents because there are several huge corporations that manufacture hundreds of variations of DEET products. There is only one small company, Coulston Laboratory, that markets a handful of competitive tick repellent products for human use that contain 0.5 % permethrin.

There are pros and cons to each product, but as a tick repellent, permethrin wins hands down. Permethrin is an insecticide derived from a chemical found in the chrysanthemum family of plants. It is a spray that is used on clothes only, and is deactivated and made less effective by the oils on our skin. Once it is sprayed on our clothing, it becomes odorless and can last for several weeks with a single application. Once it is applied, most ticks will curl up and fall off if they make contact, and will eventually die if there is prolonged exposure.

Both DEET and permethrin have come under criticism for possible human side effects. DEET has been associated with human case histories of neurological damage and even death, and products greater than 40% were restricted in some states. Permethrin has been implicated in possibly contributing to the Gulf War syndrome. However, the studies involved mixing permethrin with DEET and applying it directly to the skin of mice that were then given military vaccines.

Pros and Cons:

Permethrin-containing products that are approved for human use are manufactured by Coulston labs, and can be found under labels such as Duranon, Permanone, and Congo Creek Tick Spray. A 0.5 % veterinary permethrin product can be found in most feed stores and horse supply shops as a horse tick repellent. The veterinary products tend to cost about half the price per ounce as the human-use product.

The Minnesota Insect-Borne Disease Education Council conducted a field test in Jay Cook State Park in northern Minnesota, and found that the permethrin products outperformed the DEET-containing tick repellents. A shoe was sprayed with Duranon (0.5% permethrin). Three weeks later, it was tested against a recently sprayed shoe using Deep Woods Off (35 % DEET). Ticks that made contact with the Duranon-sprayed shoe immediately rolled up and dropped off. Ticks on the soaking-wet DEET saturated shoe continued to crawl unimpaired.

One last tip for you fishermen out there: DEET is perhaps one of the most effective fish repellents known to man. Just a few parts per million can send game fish like salmon and trout to the other end of the fish tank. If you like to keep mosquito repellent in your tackle box, you may have unknowingly contaminated all of your fishing lures! Be sure to take care not to handle any fishing tackle once you have applied mosquito repellent. Just a few parts-per-million can repel more fish than mosquitoes!

To avoid ticks:

Keep your Family Safe! Do Tick Checks!

Additional information about DEET and Permethrin

Additional information about DEET and Permethrin is presented here, which also covers questions and comments that LymeNet Europe received from readers.

What is Permethrin?

Permethrin is a synthetic chemical, used as an insecticide, acaricide, and insect repellent. It belongs to the family of synthetic chemicals called pyrethroids.

Pyrethroids are similar to the natural pyrethrins produced by the flowers of pyrethrum (plants of the genus Chrysanthemum). Pyrethrum is also the name of a natural insecticide containing pyrethrins that is made from the dried flower heads of Chrysanthemum cinerariifolium and Chrysanthemum coccineum. The dried flower are crushed and mixed with water, and this mixture can then be used as a pyrethrum spray.

Essenstially, pyrethroid insecticides are chemically stabilized forms of the natural pyrethrins. The pyrethrins are a pair of organic compounds (pyrethrin I and pyrethrin II) that occur in the seed cases of the pyrethrum. The main source is Chrysanthemum cinerariaefolium. The flowers are pulverized and the active components, the pyrethrins, are extracted and sold in the form of an oleoresin. This is applied as a suspension in water or oil, or as a powder.

Permethrin Side Effects

Permethrin is not known to rapidly harm most mammals or birds, but is dangerously toxic to cats and fish. In general, it has a low mammalian toxicity and is poorly absorbed by skin.

Toxicology and safety

Permethrin is listed as a "restricted use" substance by the United States Environmental Protection Agency due to its high toxicity to aquatic organisms.