Changes in your diet not only affect you physically,
physiologically inside,
but also mentally, how well you think,
psychologically, how well you feel.
But you’ll never know just how good you can feel
until you put it to the test and try eating healthy.
Welcome to the NutritionFacts Podcast.
I’m your host, Dr. Michael Greger.
You know I talk a lot about the killers in our food,
but what happens when we are the food?
Today we ponder the pros and cons of repelling mosquitoes with DEET.
The most dangerous animal in the world isn't the Great White,
or the King Cobra, or lions and tigers and bears.
In fact, only about 10 people die in shark attacks every year.
Coming in #2 as most dangerous?
Fellow human beings.
But the worst?
Mosquitoes.
Literally billions of people are at risk
of contracting dengue fever from mosquitoes,
and hundreds of thousands die from mosquito-borne malaria every year.
New threats like Zika continue to pose a global public health threat,
such that the World Health Organization suggested delaying pregnancy
in Zika-affected areas around the world.
What's the best mosquito repellent to wear?
There are products like permethrin,
a product originally derived from chrysanthemums interestingly,
that can be applied to clothes,
but what about repellents you actually put on your skin?
DEET is the repellent to beat, considered the gold standard
of protection when it's crucial not to get bitten.
It was developed back in the
It's long been considered the first-line mosquito repellent.
Effectiveness-wise 20% to 50% DEET repellents
provide up to several hours of protection.
That's rubbed on the skin, though.
DEET-impregnated wristbands don't work, repelling mosquitoes
only from areas covered by the band,
which I guess you could say about non-DEET-impregnated wristbands.
DEET or citronella wristbands have been clocked at working
more broadly for only
Safety-wise, DEET is considered safe
even in the second and third trimesters
of pregnancy,
and in children as long as they're older than two months.
Now it should be noted that DEET can damage plastics
and synthetic materials;
therefore, care should be taken when it's used
around plastic watches, eyeglasses, and synthetic fabrics.
Nylon is okay, but it's been found to damage spandex, rayon, acetate,
and pigmented leather, in addition to plastic and vinyl.
DEET is absorbed through your skin into your bloodstream,
but it's cleared from your system within a few hours.
Does it have any adverse effects?
DEET is probably far less toxic than many people believe.
DEET has a remarkable safety profile after now more than a half century
of use and billions of applications.
Fewer than 50 cases of serious toxic effects have been documented
in the medical literature since 1960, and most of them resolved.
Most reported cases of adverse or lethal events involved overuse
or incorrect use of the product --
incorrect use as in chugging it to commit suicide.
What's a correct usage?
Read and follow all directions on the product label.
Only apply to intact non-irritated skin.
Do not apply near eyes and mouth
and only sparingly around ears.
That's to avoid accidental eye exposure or ingestion.
It can be applied to the face, but don't spray it in your face.
Spray it on your hands and then you can dab on,
but still avoid the eyes and mouth.
Apply it to children so they don't swallow any.
Just use enough to cover exposed skin
or on the outside of clothing, not underneath.
And then once you're back inside, wash it off with soap and water,
and wash any treated clothing.
If you do have a reaction, stop using it, wash it off,
call your local poison control center.
And if you go to your doctor, bring the bottle.
So which mosquito repellent works best?
Well, in head-to-head tests, DEET crushed it.
But this was in reference to a study published about 20 years ago.
Anything new on the market that won't melt your eyeglasses?
We'll find out next.
DEET has been considered the most effective mosquito repellent.
Unquestionably, read this editorial in The Journal of Family Practice,
it should be the only mosquito repellent recommended
by physicians, with no other repellent coming close.
Given the dramatic efficacy,
it's hard to conceive that any other repellent would ever beat it.
However, there are some rare reports of severe reactions to DEET,
not the mention the fact that it can melt plastics, like eyeglass frames
and cellphone components,
and many consumers find the odor and sensation on the skin unpleasant.
Enter picaridin. Overall, studies have shown little difference
between DEET and picaridin applied at the same dosage,
with some evidence pointing to a superior persistence for picaridin,
all without the irritancy, odor, and melted glasses.
No wonder it got Consumer Reports pick
for the best overall insect repellent.
Note that concentration matters.
Their 20% picaridin product topped the list,
but at 5% it was one of their worst performing products.
Any toxicity? Adverse effects, when occurring,
primarily manifested as eye irritation/redness,
vomiting, and oral irritation,
but of course you're not supposed to eat it or spray it in your eyes.
But even unintentional ingestion was associated
with only relatively minor toxicity.
What about the electronic mosquito repellent gizmos?
Ten studies done, and all ten found that there was no difference
in the number of mosquitoes landing on people with or without the gizmos
and experiments out in the field confirm:
no effect on preventing mosquito bites.
Picaridin was roughly based on a black pepper compound,
but like DEET is a synthetic chemical.
Are there any natural repellents?
Of course, just because something is natural
does' t mean it's necessarily safe.
Strychnine is a natural product of the strychnine tree,
and ricin from castor beans is 10,000 times deadlier still.
In fact, the top 10 most toxic poisons are all natural.
But let's look at the mosquito repellent effects
of about 20 essential oils compared to a placebo
control group and to DEET.
Only five had any lasting effect at all.
Peppermint and lemongrass oil were effective for 30 minutes.
Spearmint and garlic oil started working
but didn't even last that long.
Cinnamon oil, though, reduced mosquito attraction
for one and a half hours.
The remaining essential oils had no significant effect
on mosquito attraction at any time point, and this includes citronella.
Citronella was the most widely used repellent before DEET was invented,
and is still used today in many formulations
despite inferior efficacy.
At lower concentrations, it may only last a few minutes,
and at higher concentrations citronella can cause skin irritation.
Compared to a complete protection time of 6 hours for DEET,
citronella may only last 10-1/2 minutes.
Therefore, citronella may be acceptable
for brief exposure to nuisance mosquitoes,
but it is not advised for protection if you really can't afford to get bit.
Essential oils, read this family medicine journal editorial,
have no effectiveness and are not recommended.
But that was before we learned about lemon eucalyptus,
the only plant-based repellent recommended by the CDC,
though should not be used by pregnant women
or children younger than three years of age.
Consumer Reports listed it as one of their top three picks,
warding off mosquitoes and ticks for at least seven hours.
All the other botanical products they tested failed.
But 40% lemon eucalyptus was shown to prevent bites for 4 to 7 hours
after application for aggressive species of mosquitos
and for greater than 12 hours for less aggressive mosquitoes,
a period of prevention greater than at least a 10% DEET repellent.
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Go to nutritionfacts.org/testimonials.
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To see any graphs, charts, graphics, images, or studies mentioned here,
please go to the NutritionFacts Podcast landing page.
There you’ll find all the detailed information you need –
plus, links to all of the sources we cite for each of these topics.
My last two books are “How to Survive a Pandemic”
and the “How Not to Diet Cookbook”.
Get ready this year for the launch of How Not to Age.
And, of course, all the proceeds I receive from the sales
of all my books goes directly to charity.
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whose own life was saved with evidence-based nutrition.