Mosquito repellent bracelets are increasingly popular for personal protection from mosquito bites. They are developed as a chemical-free, wearable solution intended to ward off mosquitoes, thereby decreasing the chances of bites thus avoiding vector-borne diseases such as malaria, dengue, and Zika virus. Though widely used, questions remain as to their efficacy under real-world conditions. Here we explore how mosquito repellent bracelets work, what is generally contained in them, and how their effectiveness can be measured. This will come in handy for manufacturers, consumers, and regulators.
How do they work?
Mosquito repellent bracelets work on the principle of emitting volatile compounds that function to create a barrier around the user. These compounds, which in most instances come from either natural or synthetic sources interfere with the capability of the mosquito to detect the carbon dioxide and human body odors, thus masking the presence of the user. The effectiveness of these bracelets is mainly determined by the type of repellent applied, the concentration of active ingredients, and environmental factors.
Mechanism of action
Silicone, fabric, or plastic materials with active repellent compounds are used in the bracelets. When worn, these compounds gradually evaporate into the atmosphere and create a protective cloud enveloping the human body. These clouds will protect their host from mosquitoes and give them a reduced chance of getting bitten.
Common ingredients
Most active ingredients used in mosquito repellent bracelets are of either natural or synthetic origin. Because of the difference in the properties of each active ingredient, effectiveness and length of protection, it is inevitable that the performance as a whole gets affected.
Natural ingredients
1.Citronella oil: The oil drawn from lemongrass is best known for keeping mosquitoes at bay. The pungent smell of this oil causes confusion to the mosquito’s ability to pinpoint the target. However, the short-term effect of citronella often lasts only until it evaporates or when the weather is too windy or damp, and replenishing or replacing it quite often is required.
2.Lemon eucalyptus oil: P-menthane-3,8-diol (PMD) is a naturally occurring compound in lemon eucalyptus oil, which the CDC has confirmed to be a powerful natural repellent. Compared to other plant-based oils, lemon eucalyptus oil offers longer protection and protects against many species of mosquitoes.
3.Lavender oil: Even though lavender oil is known for its calming aroma, the oil is also rich in linalool, a compound that deters mosquitoes. Lavender oil is less potent than citronella or PMD; however, the oil often gets used in combination with other repellents to complement the bracelet’s effectiveness.
Synthetic ingredients
1.DEET (N,N-Diethyl-meta-toluamide): DEET is a highly potent synthetic repellent that disrupts the mosquito’s sense of smell for its target. While DEET is used mainly in sprays and lotions, it can also be applied in a bracelet for long-lasting protection. In laboratory experiments, wristbands treated with DEET showed high levels of protection from mosquitoes but potential skin irritation issues preclude its application in some wearable devices.
2.Picaridin: Picaridin an alternative to DEET is deemed to provide similar protection but has a less greasy feel as well as a more pleasant odor. Commonly used in mosquito repellent products, it is noted to have broad-spectrum efficacy with a favorable safety profile.
3.DEPA (N,N-Diethyl phenylacetamide): DEPA is yet another synthetic repellent that has been proven to be very effective against a number of mosquito species. A recent study comparing DEET and DEPA-treated wristbands reported that both repellents gave significant protection against major vectors such as Anopheles stephensi, Culex quinquefasciatus, and Aedes aegypti.
Methods to assess the efficiency of mosquito repellent bracelets
Lab and field testing are the methods used to test the effectiveness of mosquito repellent bracelets. These methods test the control of mosquito bites by the bracelets both in artificial and natural conditions.
Laboratory-based testing
Mosquito repellent bracelets can be tested through laboratory-based testing. Laboratory-based testing is a controlled experiment to measure the effectiveness of repellents on bracelets.
1.Arm-in-cage tests: A human arm with a mosquito repellent bracelet wrapped around the wrist, is placed in a cage, into which mosquitoes enter, and the number of landings or bites is recorded. This number is compared to a control without a bracelet in order to measure the repellency of the bracelet. The arm-in-cage test represents one of the most universally accepted standards in personal protective wear testing, where protection level could be directly measured.
2.Wind tunnel tests: Such tests represent outdoor conditions, varying wind speed and direction. It considers how the compounds may be spread out from the bracelet. The technique of wind tunnel tests represents how effective a bracelet would be in dynamic conditions. It demonstrates how environmental conditions interfere with the repellent performance.
3.Cage tests with artificial attractants: Cage tests use artificial attractants, including carbon dioxide and mimic human scent, to attract mosquitoes to a test chamber containing the bracelet. Reductions in mosquito landings give an estimate of the effectiveness of the bracelet in the laboratory-controlled environment.
Field testing
Field testing is the assessment of the live performance of mosquito repellent bracelets in the field when mosquitoes are present.
1.Human landing rate tests: Volunteers wear the bracelets in localities known to be infested with mosquitoes and the number of mosquitoes landing on exposed skin is measured. The method gives direct evidence of the effectiveness of the bracelet in real life when, for example, outdoors.
2.Outdoor exposure trials: People wear the bracelets while outside throughout their daily activities, such as hiking or camping, and then test how well the product works in the environment. The number of bites inflicted is tracked in order to determine the effectiveness of the bracelet.
Factors influencing the efficacy of mosquito repellent bracelets
Environmental conditions
Major driving factors for the spread of the repellent chemicals from the wristband include: climatic factors such as wind, temperature, and humidity. Wind readily disperses the active ingredients rapidly by decreasing the concentration near the wearer. A higher humidity can also alter the evaporation rates and lower the protection offered by natural oils.
Duration of effectiveness
The duration of protection varies depending on the type of active ingredient in the mosquito repellent bracelets. Natural oils such as citronella have a tendency of evaporating fast, a factor that renders a bracelet to be frequently replaced or reinforced. Synthetic ingredients, however, such as DEET and picaridin offer longer durations of protection but increase the risk of irritating the skin.
Safety and skin sensitivity
While most ingredients used to make mosquito repellent bracelets are harmless, a few, including DEET, irritate on some skin types. Products should be tested for safety, causing no harm to humans, mostly to kids and sensitive-skinned individuals.
Regulatory compliance and standards
The mosquito repellent bracelets must meet regulatory requirements to ensure safety for proper and effective use. In the United States, mosquito repellents with registered insecticides like DEET or picaridin fall under the oversight of the Environmental Protection Agency. Compliance would prevent unsafe products from being marketed to consumers and ensure they actually do as claimed. Comparable controls in Europe, or anywhere else for that matter, would entail adequate testing and verification of efficacy claims.
Mosquito repellent bracelets represent an effective, useful product for personal prophylaxis against mosquito bites, though the effectiveness may vary with a number of factors, including formulation of the product worn or environmental conditions. Laboratory and field testing are needed to validate such performance and give consumer confidence. As the market for wearable repellents grows, so does the need for producers to test products while maintaining regulatory requirements to provide both safe and effective protection.
Ensure that your mosquito repellent bracelets meet the highest possible standards of safety and efficacy with our expert testing and validation services here at Microbe Investigations Switzerland (MIS). Contact us today to learn how we can help facilitate product development, compliance, and go-to-market success.
