Guests at the Cypress Cove Nudist Resort in Florida routinely emerge from the swimming pool and walk over to a nearby row of citrosa plants.聽聽They proceed to shake the shrubbery and then rub their hands on their thighs.聽聽No, this is not some sort of bizarre nudist ritual, it is just preparation for a spell of bite-free frolicking in the sun.聽聽The citrosa plants produce two compounds, citronella and citral, which are claimed to have mosquito repellent properties!聽
Have the nudists found a solution to a problem that has plagued mankind since times immemorial?聽聽If so, it would mean a lot more than peaceful barbecues and slap-free camping trips.聽聽It would mean the saving of lives!聽聽聽
Mosquitoes hold the unenviable record as the creature responsible for killing the most humans throughout our history.聽聽They have dispatched millions with malaria, yellow fever and encephalitis.聽聽Of course, the mosquito is not a conscious murderer;聽聽when it sinks its proboscis into our flesh, it is only trying to survive.聽聽Actually, the male is a vegetarian, it is only the female of the species that torments us.聽聽She bites, searching for a source of protein needed to nurture her eggs.聽聽Unfortunately, our blood is an ideal source of nutrients for this purpose.聽
As the female mosquito sucks blood, she injects a mix of chemicals to keep the blood from clotting.聽聽It is this mosquito saliva that can trigger the localized release of histamine, which in turn causes an allergic reaction and the associated itch.聽聽Far worse, disease-causing organisms which the prospective mother may have picked up from a previous meal may now be transferred to the new victim.聽
A great deal of research has been carried out to try and determine what makes a mosquito bite a certain individual.聽聽It is well known that some people are more attractive to the insect than others.聽聽Actually, if given the choice, many varieties of mosquitoes prefer animals.聽
Scientific evidence suggests that the mosquito selects its prey by sensing moisture, warmth, carbon dioxide and various bodily fragrances.聽聽Lactic acid, a product of muscle metabolism is a definite attractant.聽聽So is octenol, which is produced when plant material is digested.聽聽The breath of cows makes mosquitoes drool.聽聽They also find vegetarians particularly appealing.聽聽Mosquito traps that release carbon dioxide and octenol have already been used to significantly cut down on insect populations in the Florida Everglades.聽
Mosquitoes are also attracted by certain fatty acids produced by bacteria found on the skin.聽聽Since people have different microflora, they may indeed attract mosquitoes to different extents.聽聽Even certain parts of our anatomy may be more tempting to mosquitoes than others.聽聽Some species apparently prefer the fragrance of feet, others are drawn to more intimate areas.聽聽This of course may explain the nudists' habit of anointing their thighs with the citrosa scent.聽聽聽
So we are back to the citrosa.聽聽Promoters claim that the chemicals released by the plant block the mosquitoes' olfactory receptors and prevent them from zeroing in on their target.聽聽But scientific research, unfortunately, does not fully support this claim.聽聽When researchers thrust their hands into boxes filled with hungry mosquitoes, they find that citronella affords only minimal protection.聽聽聽
Consumers who rely on citronella-based bath oils, such as Avon's Skin-So-Soft, are buying into a myth.聽聽The amount of citronella it contains is not enough to repel mosquitoes.聽聽Neither is there a significant amount of coumarin, another plant-derived fragrance, which in high doses can act as a deterrent.聽聽Even the citronella candles that so many people rely on for backyard comfort owe their effectiveness more to the smoke they produce than the amount of citronella they disperse into the air.聽
Smoke really does keep the bugs away.聽聽But sound does not.聽聽The ultrasonic repellers on the market supposedly frighten insects away by mimicking the sound of the mosquito's greatest enemy, the bat.聽聽The Environmental Protection Agency in the U.S. concluded after extensive testing that none of the ultrasonic devices are effective.聽
There is one way that sound could, at least in theory, be put to a use.聽聽The characteristic buzzing of the mosquito is of course caused by the beating of its wings.聽聽When the female is desirous of mating, she produces a specific hum that brings the mate aflying.聽聽Indeed, a tuning fork struck at the right frequency will attract males.聽聽This idea could be used to trap the males and reduce the number of eggs laid.聽聽But of course, it would not prevent the females from biting.聽
So what does?聽聽The bugs can be attracted to blue light and zapped with electricity.聽聽This may make a dent in the population but some researchers suggest that the process can disperse microbes the insects may be carrying into the air.聽聽Not an attractive scenario.聽聽Better stick to chemistry.聽
Since the 1950s we have been relying on N,N-diethyl-meta-toluamide, mercifully abbreviated as DEET.聽聽This synthetic chemical does indeed bind to the mosquito's olfactory receptors and when properly used can keep the insects away for hours.聽聽The repellant effect is proportional to the concentration of DEET in a product.聽聽Unfortunately, so are the possible problems.聽
DEET can be absorbed through the skin; about 15% of a dose eventually shows up in the urine.聽聽In addition to allergic reactions, there have been rare reports of neurological problems including seizures and confusion.聽聽The risks can be minimized by not using products that contain over 35-40% DEET for adults and 10-20% for children.聽聽DEET also has an unpleasant odour and can damage some fabrics as well as plastics lenses in glasses.聽聽Still, millions of people use DEET regularly every year without significant problems.聽聽But a safer alternative is certainly desirable.聽聽And one may have been found.聽
Bite Blocker is a new entry in the mosquito repellent sweepstakes.聽聽The active ingredient, 2% soybean oil, is certainly innocuous.聽聽When mixed in a base of coconut oil, water, glycerin, lecithin, geranium oil and vanilla it protects as well as 20% DEET, and for a longer time.聽聽A single application can repel mosquitoes for ten hours!聽
There are various other folkloric repellants that people swear by although they have not been scientifically validated.聽聽Supposedly B vitamins block taste receptors that mosquitoes use when they search for blood.聽聽Advocates claim that taking yeast tablets raises the blood levels of vitamin B to an extent that affords protection.聽聽The mosquitoes may probe, but they will not bite.聽
Garlic also has a reputation as a deterrent to the sanguineous predator.聽聽But garlic loading hardly constitutes a convenient way of dealing with the problem.聽聽Neither does sleeping with pigs.聽聽According to some accounts, Mediterranean peasants capitalize on the mosquito's preference for pork over humans and allow their hogs to roam freely through the bedroom.聽
None of these remedies works for everyone.聽聽Not even DEET.聽聽Sometimes there is nothing left but bloodthirsty revenge.聽聽All you have to do is wait until the mosquito bites and then suddenly stretch the skin around the bite.聽聽This will trap the insect's proboscis and apparently cause the insect to keep sucking until it pops.聽聽One wonders what inquisitive mind discovered this phenomenon.聽
Maybe the same one that found that mosquitoes hate the scent of Bounce, the little sheet impregnated with fabric softener that we usually toss in the dryer.聽聽It seems that tying a sheet through a belt loop keeps the bugs away.聽聽Sounds great!聽聽But of course, having no belt loops, this does present a problem for nudists.聽聽I guess they will just have to keep shaking those citrosa plants.聽聽Or put on the DEET or the Bite Blocker.
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