08 August 2024
Summertime is mosquito time. These annoying little insects can drive holidaymakers by lakes to bouts of frenzied slapping of their arms and thighs and cause itching that can deprive them of sleep. What makes us so attractive to mosquitoes in the first place, and how is it that they can be driven away with insect spray?
Mosquitoes fly at people. To be precise, they are drawn to us by our smell — to be more exact still, by our exhalations. It’s the carbon dioxide in the air we breathe out that sets mosquitoes on our trail. Because pregnant women breathe for two, as it were, and also have a higher body temperature, they are among the most popular victims of female mosquitoes. These female fliers need the iron and proteins from their feast of blood to develop the eggs that will hatch into their brood.
You smell so good
The mosquito mothers-to-be also smell our sweat and the cocktail of scents on our skin, including ammonia, lactic acids and fatty acids. Depending on our genes and our current metabolism and hormone balance, we produce these substances in different quantities. This is one of the reasons why mosquitoes bite some people more often and others less often. Different mosquito species also seem to have certain preferences: Some are more into ammonia, while others make a beeline for lactic acid. It’s also possible that our blood type makes us differently attractive to mosquitoes: A Japanese research group found that subjects with blood type 0 were twice as attractive to the Asian tiger mosquito as those with blood group A. Since only 64 people were involved in the study, the findings are only partially reliable.
Reducing our attractiveness
One thing is certain in any case: We can all temporarily make ourselves less attractive to mosquitoes. Taking a shower will rinse the enticing sweat cocktail off our skin, protecting us in the short term from being bitten. Or we can use a fan to dissipate our body odour and confuse the mosquitoes’ navigation system. But unfortunately, we can’t stand in the shower all day. And we won’t always have access to a fan when we’re out for a walk.
This is where insect sprays come into play. The magic word here is repellents. These may contain, for example, diethyltoluamide (DEET) or icaridin, both of which rarely occur in nature. Applied thoroughly and without gaps, these will mask our body’s own scents. They make us invisible not only to mosquitoes, but also to other insects – it’s almost like wearing an invisibility cloak from a spray can.
Always on the go
DEET was developed and patented by the US Army in the 1940s. It was mainly used in foreign deployments in mosquito-infested areas in Southeast Asia, for example in the Vietnam War. DEET was also approved for civilian use in 1957 and marketed from the mid-1960s. Excluded from this approval were children under two years of age and pregnant or breastfeeding women. If you were one of these, you just had to do without. And unlike skin-friendly icaridin, DEET attacks plastics and leather. It therefore needs to be kept away from sunglasses and watch straps. According to a study, icaridin can in turn harm the larvae of caudates or other amphibians. So, if you’re planning to go wild swimming in the summer, you might be better advised to use other means instead.
Home remedies don’t help
Home remedies such as essential oils are not recommended. In tests carried out by the consumer organisation Stiftung Warentest, products based on essential oils worked for a short time at best and were significantly less effective than chemical mosquito repellents.
PMD straddles the dividing line between the two. This was originally extracted from the essential oil of eucalyptus, but is synthetically produced for protection from insects. It has been proven to offer protection against pesky biting insects but is weaker than icaridin and DEET and only lasts for four hours.
Depending on your personal tastes, however, mosquito bracelets can be an eye-catcher, and citronella candles, garden torches or oil lamps with tea tree or other essential oils can create a nice atmosphere – but what they won’t do at all is stop mosquitoes from biting you. But at least you will end up with a nicely scented backdrop as your involuntary blood donation helps bring the next generation of mosquitos into being.
