Advisory by Shane Liaw, Guardian Pharmacist
To get the most out of outdoor activities, take care to protect yourself from annoying insects, especially mosquitoes. Most insect bites, including mosquito bites, can cause skin eruptions, rashes and itching, which can be uncomfortable and induce scratching. More seriously, mosquito bites come with the risk of infections such as dengue fever. Hence, it is important to apply repellents on exposed skin surfaces or clothing prior to outdoor activities.
Types of repellents
Mosquitoes and other blood-feeding insects are attracted to the carbon dioxide from our breath and certain skin odours. Although the exact effects that mosquito repellents have on the winged insects are not fully understood, it is thought that some of the chemicals used in mosquito repellent may confuse the senses of the mosquitoes by blocking their ability to detect skin odours. Here are some of the chemicals that are commonly found in mosquito repellents.
DEET (N,N-Diethyl-meta-toluamide)
DEET is very effective against certain insects, including mosquitoes, ticks or fleas. In Singapore, DEET is available in spray or lotion form with concentrations ranging between 7% and 25%. Products with DEET concentration of no more than 10% are considered safe to use on young children and infants from two months of age.
While the effectiveness of DEET preparations does not increase with concentration, higher concentrations do confer a longer duration of protection.
Picaridin (Hydroyethyl isobutyl piperidine carboxylate)
Picaridin is also known as icaridin. The advantage of using picaridin over DEET is that this chemical does not damage plastic or man-made fabrics. Likewise, picaridin is also an effective repellent option and has also been formulated into sprays. This is also safe for use in infants from two months of age.
Citronella oil
Citronella oil is a plant-based ingredient which is useful for its insect repellent ability. However, citronella is effective only for shorter durations and hence, frequent reapplications are required. Citronella oil repellents are available in sprays and extended-release patches for use on clothing.
Ethyl butylacetylaminopropionate
Also known as IR3535, this compound in derived from the naturally occurring amino acid beta-alanine, which is a building block for proteins. Mosquito repellents containing IR3535 are formulated in spray form in concentrations between 10% and 30%. IR3535 preparations are usually safe to be used on children over the age of two.
How to use repellents
Insect sprays are simple to use and can be carried along for regular use whilst outdoors. For most repellent sprays, hold the bottle about 15 to 20 cm away from your skin or clothing and spray in a slow, sweeping manner. Repellent sprays should not be applied over cuts, wounds or irritated skin.
To avoid getting the contents into the eyes, mosquito repellent should not be sprayed directly onto the face. Instead, you can spray the repellent onto your palms and rub it carefully onto your face, leaving out areas surrounding the eyes and mouth.
Insect repellent patches are also convenient and generally safe to be used on young children and infants. These patches typically contain citronella oil and can last from eight hours to a few days. It is important to apply these patches on fabric as adhesion on skin may cause skin irritation.
Common side effects of repellents
Skin reactions such as rashes and itchiness may occur with the use of repellent sprays or lotions. These reactions are usually mild and tend to subside with discontinuation of the repellent.
Eye irritation may occur when contact has been made with the vapour. Immediate washing of the eyes under a running tap and referral to a doctor is advised.
Other tips to avoid mosquitoes
Aside from using repellants, you can also consider limiting your time spent outdoors, especially during dusk or dawn as most mosquitoes are active during these periods.
If you cannot avoid going outdoors, do consider wearing long-sleeved clothing to minimise skin exposure. In addition, do avoid wearing dark- or bright-coloured clothing, which makes you more visible to mosquitoes. Light or khaki clothing is less likely to attract mosquitoes.
