My wife was seriously bitten by a mosquito recently. I have since become motivated to find out why mosquitoes seem attracted to her and not to me. I have discovered why they bite, what attracts them to particular people and which insect repellents work best. By sharing what I've found I hope I can make your life a little easier.
Let me say first of all that we shouldn’t ignore the risks. I have found out that diseases transmitted via mosquitoes are expected to be responsible for the deaths of 1 of every 17 people currently alive! Also mosquitoes that switch their hosts seasonally can transmit diseases from animal to humans but they cannot transmit HIV.
Anyway, enough of the scary stuff......
Why do Mosquitoes bite?
That’s easy. Only Female mosquitoes bite. THEY NEED A BLOOD MEAL IN ORDER TO PRODUCE EGGS. No wonder they seem so determined!
Female mosquitoes usually feed every 3 to 4 days. In a single feed they can consume more than their own weight in blood. Certain species prefer to feed at twilight or night time whilst others bite mostly during the day.
So, what attracts them?
- Mosquitoes are guided by three things on their journey to their chosen host – Sight, Heat and Smell.
- When people suggest wearing dark clothing to deter mosquitoes they are generally referring to those mosquitoes that prefer to feed during the day.
- Smell is considered to be the most important stimulant as the mosquito nears its host.
- There are over 100 volatile compounds detectable in human breath.
- Of these Carbon dioxide and Lactic Acid are the two best known mosquito ‘favourites’.
- Mosquitoes can detect carbon dioxide (also released through our skin) at a distance of up to 36 metres.
- Mosquitoes have chemoreceptors on their antennae (in other words they can pick up the presence of chemicals) and these are stimulated by the presence of lactic acid.
- At close range skin temperature and moisture (e.g from sweat) serve as attractants. The extent of this depends on the species of mosquito.
- Your overall smell has a greater influence than carbon dioxide and lactic acid alone.
- So, please note that perfumes, soaps, lotions and hair care products may also attract mosquitoes (and they can dilute the effects of repellents).
- In general, they are attracted to adult humans more than to children.
- Some humans become less attractive to them as they get older.
- In general, they are more attracted to men than women.
- In general, larger people are more attractive – possibly due to a greater output of heat and/or carbon dioxide.
Which insect repellents actually work?
I actually found a scientific study which revealed that, following many tests, it has been shown that plant-based repellents are generally less effective than DEET-based products. Those tests apparently required major distributors of natural insect repellents to provide scientific data, if available, to back up their own claims about their products.
I guess one can’t ignore such studies but we have to remember that scientific data isn’t always available for things that work and, for many people, such data isn’t always needed. After all the natural repellents that are selling well presumably do work, otherwise surely people wouldn’t go back for more. Would they? What seems certain though is that plant based repellents (e.g. ones with Citronella) are shorter lasting and therefore require more frequent application.
The following plant extracts have shown some repellent qualities: Citronella, cedar, lavender, pine, cinnamon, rosemary, basil, thyme, garlic, peppermint, verbena, geranium. When tested, most provide a short lasting protection only.
One experiment, I thought was interesting, concluded that people sitting near burning Citronella candles had 42% fewer bites, which is pretty good; however, people sitting next to ordinary burning candles had 23% fewer bites, anyway. That is probably because candles exude warmth, moisture and carbon dioxide which, as we have seen, attract mosquitoes.
DEET (N,N-diethyl-3-methylbenzamide) based repellents are, according to the above mentioned study, without question, the most effective insect repellents currently on the market. However, the product has to be used with some care to avoid any toxic reaction.
DEET products are also effective against biting flies, fleas, ticks e.t.c.
DEET comes available in solutions, lotions, sprays, creams, gels, aerosols, pump sprays and impregnated wipes/towelletes.
As a general rule the higher the concentration of DEET the longer lasting the protection. For casual use 10% to 35% will provide adequate protection in most conditions but for children it’s probably best to make this no more than 10%. However, in danger zones around the world the concentration might need to be significantly higher.
When DEET based repellents are combined with permethrin-treated clothing almost 100% bite protection is achieved. However, DEET repellents themselves are also effective when applied directly to clothes. They can also be applied to windscreens, mesh nets, tents or sleeping bags. If, in between use, treated materials are stored in sealed plastic bags the repellent qualities could last for weeks. DEET does not damage natural fibres but can damage plastics, other synthetic fabrics, leather and painted or varnished surfaces - so apply it carefully and always read the instructions.
Whichever repellent you apply you will need to consider the following:-
- Apply the repellent evenly to all areas of exposed skin – even small gaps in application leave you vulnerable.
- Rain, sweat, higher temperatures, windy environment can all reduce the repellents effectiveness.
- A 10% increase in temperature can reduce protection time by 50% so conditions will affect required frequency of application.
Just a quick comment about anti mosquito electronic devices – most have been shown to be ineffective as female mosquitoes are more attracted to humans than to the devices. They do however kill a lot of male mosquitoes which, as we know, don’t bite.
One more thing you can do, of course, is to limit their breeding – i.e. remove anything that allows water to collect, such as old tires, blocked gutters, bird baths, buckets e.t.c. Be aware that the female mosquito lays several hundred eggs at a time!
Just to follow up on my wife's situation she has been advised to take oral antihistamines, on future ocassions, without delay. They minimize bad reactions to mosquito bites.
That’s about it. I am no expert but hopefully the above information will help, at least in some way, to help you protect yourself and those you care about against mosquito bites.