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---
  layout: post
  title: DEET Me Up
  author: Joe Schwarcz
  source: McGill Blogs
---
  HYPERLINK
"http://blogs.mcgill.ca/oss/2016/07/21/deet-me-up-how-best-to-repel-a-mo
squito/"  DEET Me Up: How Best to Repel a Mosquito 

  

When it comes to protection from mosquitoes, opinions are abuzz.  Burn
citronella candles.  Wear repellant bracelets.  Douse yourself with
Avon’s Skin-So-Soft.  Eat garlic.  Take vitamin B1 supplements. 
Use concentrated DEET.  Use dilute DEET.  People are confused. 
Needlessly.  There are many questions science cannot readily answer,
but the question of what is the most effective mosquito repellant is not
one of them.  That’s because it doesn’t take rocket science to
design an appropriate study.  You don’t need sophisticated equipment
and you don’t have to extrapolate from rat studies.  All you need are
some human volunteers who are willing to stick their bare arms into a
cage of hungry female mosquitoes.  And that is exactly what researchers
had fifteen volunteers do at the University of Florida in a study
reported in the New England Journal of Medicine.  And now we know what
works and what does not.

This study was very carefully done.  Temperature, humidity, density of
the mosquito population and state of hunger of the insects were all
controlled.  Sixteen popular products were purchased and tested
repeatedly with the time until first bite being accurately measured. 
Lets’ start with what doesn’t work.  You can forget about any of
the “repellant” wristbands.  They kept mosquitoes away for the
stunning time of about twenty seconds.  Avon’s “Skin-So-Soft” may
make your skin feel soft but will only keep the bugs away for about
twenty minutes.  After that your skin will get pretty bumpy from all
the bites. Other citronella preparations fared even worse.  So unless
you are willing to walk around constantly spraying yourself, forget the
citronella products.  So what works?  N,N-diethyl-m-toluamide or
“DEET.”

Some people worry about DEET because they’ve heard reports of toxic
reactions and are suspicious of the substance because it is a synthetic
chemical.  Whether a substance is synthetic or not has nothing to do
with its safety profile.  Indeed DEET has a remarkable safety record. 
It is estimated that since its introduction around 1960, about 8 billion
doses have been applied to humans.  And this has resulted in fewer than
50 serious toxic effects of which more than 75% resolved with any
further problems.  In the handful of cases where there were residual
effects, there was heavy, frequent application over the whole body. 
The New England Journal study has now shown that such applications are
not necessary.  A DEET concentration of 24% provided five hours of
protection.  Even a 5% concentration, which can be used on children,
kept the mosquitoes away for an hour and a half.  DEET should not be
used under clothing, on an open cut or with sunscreen.  So there it
is.  Look for a product that has between 25 and 30% DEET for adults and
apply it every four hours or so.  For young children use the 5%
stuff.  If you really want something “natural,” although I don’t
know why that should be appealing, “Bite Blocker” made with soy oil
offers about ninety minutes of protection as do products made with
eucalyptus oil.  And if you think that citronella has a pleasant smell,
you’re not alone.  Mosquitoes like it too.

A recent study by Consumers Union corroborated these results.  “Off
Deep Woods” with 98% DEET kept mosquitoes and ticks away for over ten
hours.  Products with 20-34% DEET worked for at least five hours.  The
best non-DEET product was Repel Plant Based Lemon Eucalyptus which
contains p-menthane-3,8-diol.  It worked for about three and a half
hours.  Products with picaridin did not work well, neither did a shirt
treated with permethrin.

 

Joe Schwarcz – July 21st/2016