What Does Concentration Mean?
Concentration means the amount of DEET (the active ingredient) in a repellent product. For ticks, the CDC notes that a minimum 20% concentration is important for protection that lasts several hours. For mosquitoes, the entire range of concentrations are effective. The duration of efficacy depends on many factors, including how much you perspire, and other considerations. The important thing to remember is that 5% works as well as 100%, just not as long. Most experts suggest matching the product to the duration of exposure (for mosquitoes). Use products from 5-30% in the US.
Why is an EPA Registration Number important?
The US Environmental Protection Agency (EPA) has issued registration numbers for active ingredients used in repellents sold in the U.S. This means that each of these ingredients has been evaluated by EPA for both safety and efficacy. In addition, end-use products, such as the repellents available for consumer use, are also registered with EPA and have been subject to the same evaluation as the ingredients.
Products marketed as repellents that do NOT carry this EPA registration number are generally regarded by experts as minimally effective against mosquitoes. For more information on non-EPA registered repellents and efficacy, please click here and here.
Expiration dates are not required to appear on repellent labels. Consider replacing products that have been open longer than three years.
Contacting the Company
If you have questions on product expiration or other topics, please contact the product manufacturer. Most companies that formulate DEET-based products provide a toll-free number for consumers, which can be found either on the label or the manufacturer’s website.