Determining Repellent Effectiveness

Higher Percentage Means Longer Lasting

A higher percentage of DEET in a repellent does not mean that your protection is better—just that it will last longer.

DEET concentrations higher than 50% do not increase the length of protection. 

Based on a recent study:

  • A product containing 23.8% DEET provided an average of 5 hours of protection from mosquito bites.
  • A product containing 20% DEET provided almost 4 hours of protection.
  • A product with 6.65% DEET provided almost 2 hours of protection.
  • Products with 4.75% DEET or 2% soybean oil provide roughly 1-1/2 to 2 hours of protection.

Choose a repellent that provides protection for the amount of time you will be outdoors. A higher percentage of DEET should be used if you will be outdoors for several hours, while a lower percentage of DEET can be used if time outdoors will be limited. 

You should also re-apply a product if you are outdoors for a longer time than expected, before you start to be bitten by mosquitoes.

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