Perfume won’t protect you from mosquito bites

VictorissecretThe headlines have been awash with claims that a popular perfume may repel as many mosquitoes as those regularly recommended by health authorities. Could it be true?

In short, no. There is little surprise that the results of this recently published study in the Journal of Insect Science has attracted so much attention. Everyone loves the idea that some unexpected substance could be used as a mosquito repellent. Even better if it performs as well, or even better, than those such as DEET or picaridin that are widely recommended by health authorities.

The scientists tested a range of commercial insect repellents. Three formulations of DEET based repellent, an oil of lemon eucalyptus (aka PMD) based repellent, three botanical-based repellents, a mosquito repellent patch (Vitamin B), a product not specifically designed as a repellent but often quoted as being effective (Avon skin so soft) and the perfume. Why include the perfume at all?

The logic behind including the perfume was a good one. It is often said that floral perfumes and other cosmetics attract mosquitoes. I’ve never thought this is actually the case. I mean, there is stronger evidence that mosquitoes re attracted to smelly foot bacteria than pleasant smelling cosmetics! I always suspected that the idea comes from the fact the mosquitoes (mostly the non-biting males) will feed on plant sugars. However, it was worth including in this study. Always good to gather some quantitative evidence on the response of blood-seeking mosquitoes. It could be a good opportunity to bust (or perhaps confirm) some urban myths.

I’ve written before about how you can test mosquito repellents. While the “arm-in-cage” methodology typically provides the best indication of how a mosquito repellent will perform, there are other methods commonly employed. In this case, the researchers used a “Y-tube” setup. This system basically allows mosquitoes to make a choice as to whether they preferentially fly towards one or the other ends of the tube. If you insert a hand treated with a substance into one end and another untreated hand as a control into the other, it is possible to measure the overall repellent effect by tracking the movement of mosquitoes.

Firstly, it is interested to note that the researchers found that some mosquitoes were attracted to the hand treated with DEET. If I was conducting an “arm in cage” test. I would be very surprised if I had any mosquitoes biting a DEET-treated arm within 2h of application. In one study, I found an approximately 7% DEET-based repellent stopped bites for a little under 2h. It makes me wonder how many mosquitoes may fly up to tube towards the treated hand but, given the chance, would actually bite the hand?

Fewer mosquitoes were attracted to hands treated with oil of lemon eucalyptus, not surprising either given this product is regularly recommended as an effective repellent by health authorities.

The testing of the perfume provided the headline grabbing results! For the first couple of hours, there wasn’t much difference in the proportion of mosquitoes repelled by the perfume compared to the other repellents. Why? It may be related to the strength of the odour overpowering the sensory organs of the mosquito. I think this is how some strongly smelling essential oils can provide some protection. It masks the normal chemical cocktails of smells on our skin that attracts mosquitoes.

We all know how overpowering the smell of some cosmetics can be. In this case of this experiment, a relatively high dose of the products as used. The authors make note of this too when they state “It must be noted that the concentration of perfume we used in this test was rather high and that lower concentrations of the same fragrance might have different effects.”

Could this perfume be used as a repellent?

Studies like this provide some fun headlines but they can be misleading to the public. What “works” for a relatively short period in a small laboratory based study does not necessarily stand up the practicalities of real life.

Notwithstanding the expense (the perfume is about AUS$80 for 100ml compared to less than AUS$10 for about the same amount of DEET-based repellent) I must admit that for some of these products, the smell can be so overpowering that applying them to large areas of skin would probably be more unpleasant than the bites of mosquitoes!

When trying to help the public choose and use mosquito repellents more effectively, it is critical that health authorities stick to products that are currently registered for use as a mosquito repellent and that have been demonstrated to provide suitable protection from biting mosquitoes over extended periods of time.

Perhaps the most important finding of the paper is not that the perfume repelled some mosquitoes but that patches infused with Vitamin B provide absolutely no protection from mosquitoes. This is one urban myth that never really seems to go away!

We also know that Victoria’s Secret perfume doesn’t stop bed bugs invading lingerie stores!

[The image used at the top of this piece is taken from here.]

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