6 mins

Putting up barriers against mosquitos

Now you know all the options, here we explain just why they are necessary and how you can maximise your protection against mosquitoes

Prevent mosquito bites and you'll stop the risk of disease (thecrazyfilmgirl)

What are the risks?

There are – sadly – a host of diseases to be caught from mosquito bites, ranging from the inconvenient to the rapidly fatal.

The big problem with malaria and many other ‘tropical diseases’ is that the symptoms they cause are not peculiar to any one disease so diagnosis is difficult – even for doctors. Any nasty diseases acquired in the tropics or sub-tropics – including those spread by mosquitoes – tend to cause fever above 38ºC. 

In regions where mosquitoes transmit serious disease such a fever should therefore send you scuttling to a doctor for proper diagnosis and treatment. Most infections – if promptly treated – will cause no long-term problems. 

Four species of malaria commonly infect people. Falciparum malaria is the form that can cause cerebral complications and kills by parasitising up to half of all the red blood cells in your body. Once it gets this bad, no treatment on earth is likely to save you. The other forms of malaria are rarely deadly but can linger and can be difficult to completely eradicate from the liver. 

Liver failure is the key to why yellow fever is so deadly – this viral infection gets its name from the jaundice it causes. It is difficult to treat and perhaps a quarter of those infected die from yellow fever; the vaccine is completely protective though. 

Dengue is another viral infection that has no specific treatment. It causes ‘break-bone fever’, so called because of the joint and muscle aches that accompany the illness. Generally this resolves without complications or long-term problems but sometimes a dangerous haemorrhagic form develops where the blood-clotting mechanisms become deranged. 

Given that there are a range of serious mosquito-borne infections, only some of which are treatable, and that no anti-malarial medication is 100% protective, it is wise to avoid bites as best you can.

Personal choice

Your risks of serious disease, as well as your individual sensitivity to bites, are factors to consider when deciding whether to choose a natural or a chemical repellent. Many of the ‘naturals’ work well enough but if I was in a high-risk zone where my life depended on it, I’d pick the most effective product I could find, even if cosmetically it might not be so pleasant to use.If you are using a product that is new to you, test it on yourself before you go as almost anything that is applied to the skin has the potential to cause an allergic reaction in a minority of people. 

Those who have eczema, or inflamed, broken or very sensitive skin may not be able to tolerate DEET-based repellents. (Note that if your eczema is poorly controlled, you should try to get your doctor to sort this before departure.)

Maximum effect

Once you have selected and tested your repellent it is important to be aware that the way you use it influences its effectiveness. You need to try to apply repellent evenly and not leave any skin unprotected, especially in very bitey environments. However, it is unwise to apply repellent under socks or other clothes items.

Manufacturers advise washing repellent off when it is no longer required, but that advice can be hard to follow. Yes, if you are retiring under a nice, safe insecticide-impregnated mosquito net then the repellent is theoretically redundant, but what if you need to trek down the corridor for a middle-of-the-night pee?

You should be careful when using DEET. It can dissolve plastics, including spectacles and watch-faces. It will also render condoms microscopically perforated, so hands must be washed before handling any of these vulnerable materials.

Even the best repellents need to be reapplied frequently – but how frequently? Unfortunately it is impossible to give fail-safe rules but it is important to register that, even when a repellent claims protection for ‘up to eight hours’, in the worst conditions it may only protect for perhaps two hours.

Unfortunately regions with high bite prevalence are also often regions with high ambient temperatures and high humidity; in these conditions you’ll probably need to reapply repellent every couple of hours. The hotter the climate and higher the humidity, the quicker you will sweat it off. 

Clearly repellent needs to be reapplied after swimming or if the skin has been rubbed with a towel. Should you need to apply both a sunscreen and a repellent, the sunscreen goes on first, is allowed to soak in for 30 minutes, then the repellent goes on afterwards.

Repellents are only part of the armoury against insects. Using several approaches reduces any (albeit theoretical) problems with toxicity as well as keeping costs down and reducing the number of bottles of repellent that you need.

Repellents should be used intelligently and in association with insecticide sprays on clothes, nets and even the precaution – for medicinal reasons only, of course – of retiring to a screened bar.

Dr Jane Wilson-Howarth’s 'Bugs, Bites & Bowels' is packed full of travel health tips and advice

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