Sunscreen and Insect Repellent - Which Goes On First?

If you’re in a country that requires you to apply sunscreen, there’s a good chance you’ll also need to apply insect repellent. But which goes on first for the most effective protection?

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Sunscreen vs DEET Photo © Getty Images/Orbon Alija

Is it true that putting sunscreen on first will cancel the effects of insect repellent?

DEET and Sunscreen

The debate on the application of sunscreen with DEET is an old one. Using DEET insect repellent with sunscreen decreases the effectiveness of the sunscreen by about 30-40%. So if using both at the same time, be prepared to re-apply sunscreen more often than if using sunscreen alone.

There are several commercial products that combine DEET and sunscreen into one cream or lotion. These are generally not as good as using two separate products.

Should You Apply Deet or Sunscreen First?

For several years, the Travel Medicine community has preached application of sunscreen first and then DEET applied over the sunscreen.

This information comes from the CDC Yellow Book. Put the sunscreen on first, allow a period of about 5-10 minutes to allow the sunscreen to dry, prior to applying DEET insect repellent. The UK's NHS Fit for Travel gives the same advice as the CDC.

Advice from the International Association for Medical Assistance to Travellers also says to apply the sunscreen first and DEET second. 

Studies on DEET and Sunscreen

It's important to note that evidence to support the application of sunscreen before or after DEET based insect repellent is limited.

Some medical experts have suggested that whichever way the two products are applied has little effect on the decreased efficacy of sunscreen. This decreased protective effect of sunscreen when used with DEET is unavoidable due to the product's chemical interactions.

It's been hypothesized that the sunscreen applied over the DEET may interfere with the evaporation of the DEET, thus lowering its ability to repel mosquitoes. However, there is no peer reviewed literature to back this statement.

The other belief is that DEET might be less absorbed by the skin if sunscreen were applied first, protecting the skin. Obviously, the goal is to reduce the skin's absorption of DEET as much as possible. This is also another theory without decent evidence.

Basically, there is no clear, scientifically robust evidence that support these theories; therefore a substantial study needs to be done examining this issue further.

In the meantime, it's advised you reapply both often to avoid being sunburnt and keep the bitey beasts at bay. This is particularly important if you go swimming, shower or sweat a lot.

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10 Comments

  • Robert Diller said

    I am no expert in any way shape or form, but I would hypothesize the since sunscreen absorbs into the skin, it would cause the Deet to absorb into the skin more if it were applied after the deet. The idea is that the sunscreen would act as a catalyst when mixed with the Deet. This may occur either way dpending on the ingredients in the suncreen or sunblock.

  • Stacy Z said

    There sunscreens that come with bug repellent included now. You can kill two birds with one stone!
    Stacy
    http://provenpestprevention.com

  • Stacy Z said

    There sunscreens that come with bug repellent included now. You can kill two birds with one stone!
    Stacy
    <a href="http://provenpestprevention.com">propane mosquito trap</a>

  • Mike M said

    Just an FYI, from my unscientific research everything I've read said the combo products are not as effective as the2 separate ones.

  • SAM said

    Interesting. A patient brought this to my attention.

    The link to see "the new advice" does not work so I am unable to review the info. As a member of ISTM for 25 years, I do not recall ISTM issuing this or any other advice. Yes, the professionals who are members do enormous research that is published in many scholarly journals, textbooks as well as the lay media. Actual health advice for public consumption is generally left to the CDC, WHO and ECDC or whatever governmental body has oversight in each sovereign nation.

    And yes, the combination products are less effective in the sunscreen component, necessitating very frequent reapplication.

  • Fred cutler said

    Sunscreen first then DEET. Then further applications of sunscreen. Is that the best, or worst of all cases?

  • Winnie said

    What's recommended with reapplication? If you need more sunscreen do you also need to reapply the deet?

  • Nichole said

    Hi,

    There is a fair amount of evidence for the things you say there is no evidence for. A quick Google Scholar search of "deet and oxybenzone" will turn up a series of papers out of Canada by Ting Chen. Happy reading!

  • Whitney Camarena said

    The percentages of DEET in bug spray relate to length of time that it will be active, NOT strength of effectiveness. Over 50%, there is no evidence that supports longer lasting protection. So, save yourself the money, go for 50% DEET products, follow the reapplication instructions, and apply sunscreen first then bug spray (DEET or any repellent registered with the EPA.

  • Rebecca Kleitz said

    What if you use DEET free bug repellent? I just cannot bring myself to use DEET products. I've had good results with Skeeter Beeter repellent that I buy at Lowe's. . .it's very expensive, but worth it to me, cos I can also use it on my pets. . .six cats and two dogs.

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