N,N-Diethyl-meta-toluamide, commonly known as DEET, is a synthetic chemical widely recognized as the active ingredient in many insect repellent products. This compound has been used by the general public since 1957. With increasing concerns over tick-borne illnesses such as Lyme disease and Rocky Mountain spotted fever, understanding which protective measures are effective is important. This article investigates the specific role of DEET in preventing tick bites, detailing its mechanism of action, proper use, and comparison with other available options.
DEET’s Effectiveness Against Ticks
DEET is an effective tool in a tick prevention strategy, working by confusing the parasites rather than killing them on contact. It is registered by the Environmental Protection Agency (EPA) for use against ticks, along with a wide variety of other biting arthropods. Studies have shown DEET to be approximately 85% to 89% effective at repelling ticks when applied correctly.
The compound functions by jamming the tick’s sensory receptors, which they use to detect chemical signals like carbon dioxide and lactic acid emanating from a host. By interfering with these receptors, DEET essentially masks the human scent, preventing the tick from recognizing a person as a potential blood meal. The duration of this protection is directly linked to the concentration of DEET in the product, though not in a simple linear fashion.
Higher concentrations do not equate to a stronger repellent effect, but they do extend the period of protection. For instance, a product with a 10% DEET concentration may offer about two hours of protection, while increasing the concentration to 25% or 30% can extend that time to five hours or more. Research indicates that concentrations above 50% offer negligible additional duration of protection against ticks.
Proper Application for Maximum Tick Repellency
Achieving maximum protection requires careful and targeted application of DEET to both exposed skin and clothing. Repellent should be applied sparingly, using only enough to lightly cover all exposed skin, avoiding application directly under clothing. Ticks typically crawl upward from the ground, making the lower body, including socks, shoes, and pant cuffs, particularly important areas for treatment.
When applying to the face, it is safest to spray the product onto your hands first, then carefully pat it onto the face, taking care to avoid the eyes, mouth, and nostrils. The chemical should not be applied over cuts, wounds, or any irritated skin, as this can increase absorption. Reapplication of DEET should only occur when the initial application wears off, and should not exceed once per day.
Using products that combine sunscreen and DEET is generally advised against because sunscreen needs to be reapplied frequently, while DEET does not. Repeatedly applying a combination product can lead to unnecessary and excessive exposure to the repellent. Following the specific instructions on the product label will ensure the intended duration of effectiveness is achieved.
Alternative Tick Repellents
While DEET is effective, several other EPA-registered active ingredients offer protection against ticks. Permethrin is one such option, though it is used strictly as a fabric treatment, never on the skin. Permethrin functions as a contact insecticide, meaning it kills or repels ticks that land on the treated fabric, providing a secondary layer of defense.
Once applied to clothing and gear, Permethrin bonds to the fibers and remains effective through multiple washings, lasting for weeks. This makes it a popular choice for treating boots, hiking pants, and backpacks. Combining Permethrin-treated clothing with a repellent on exposed skin offers the most comprehensive protection strategy.
Another effective topical repellent is Picaridin, a synthetic compound resembling a natural chemical found in black pepper plants. Picaridin is often favored because it is odorless, non-greasy, and does not pose a risk of damaging plastics or synthetic materials, unlike DEET. Products containing 20% Picaridin can provide up to eight hours of protection against ticks. Oil of lemon eucalyptus (OLE), which is not the same as pure lemon eucalyptus essential oil, is an EPA-approved plant-based alternative. While OLE provides tick protection, its duration of effectiveness is generally shorter than that offered by DEET or Picaridin.
Safety and Usage Guidelines
DEET is considered safe when used according to label directions. For children older than two months, health experts recommend using products that contain no more than 30% DEET. Repellent should never be applied to infants younger than two months of age.
When applying repellent to a child, an adult should spray the product onto their own hands first and then rub it onto the child’s exposed skin. Care must be taken to avoid a child’s hands, as they frequently put their hands in their mouths or near their eyes. Upon returning indoors, all treated skin should be thoroughly washed with soap and water. Clothing that has been treated with the repellent should be laundered separately. Applying the product in an open, well-ventilated space helps prevent the inhalation of the spray.