Mosquitoes are transmitters of a variety of deadly diseases, including malaria, dengue, and Zika virus. Mosquito repellents are vital in the fight against mosquito-borne diseases. This article goes into the science of mosquito repellents, investigating their chemistry, the methods by which they repel mosquitos and the different mosquito repellent testing available.
Understanding mosquito behavior and their attraction to humans
Mosquito sensory perception
A variety of sensory signals are used by mosquitoes to find their hosts. These indicators include body temperature, CO2, and certain chemicals that are present in perspiration. Because of their highly developed olfactory systems, female mosquitoes—which bite and consume blood—are able to perceive stimuli from a distance.
Attraction to bodily odor and carbon dioxide
Carbon dioxide emitted by people and animals is a main mosquito attractant. When mosquitoes detect CO2, they follow the gradient to find their host. Specific chemicals in human sweat, such as lactic acid, ammonia, and certain fatty acids, can attract mosquitos. These chemical clues differ from person to person, which explains why some people are more susceptible to mosquito bites than others.
The chemistry of mosquito repellents
Active ingredients in mosquito repellents
Active ingredients in repellents interfere with mosquitoes’ ability to perceive their surroundings, making it more difficult for them to locate their hosts. DEET (N,N-Diethyl-Meta-Toluamide), picaridin, IR3535, and natural oils like citronella, eucalyptus, and lavender are the most widely used active ingredients in repellents.
DEET
DEET is a highly efficient and extensively used insect repellent. Its chemical structure, N,N-Diethyl-meta-toluamide, affects the function of mosquito olfactory receptors, particularly those sensitive to lactic acid and CO2.
Picaridin
Synthetic repellents like picaridin, also referred to as Icaridin or KBR 3023, offer similar levels of protection as DEET. It functions by stopping mosquitoes from identifying host cues, just like DEET does. Because picaridin has no smell and is less greasy, it is a preferred option for many people.
IR3535
Synthetic amino acid derivative IR3535 (Ethyl butylacetylaminopropionate) imitates the skin’s naturally occurring component beta-alanine. It functions by perplexing mosquitoes’ olfactory sensors, preventing them from locating their prey. Pregnant mothers and children can benefit greatly from the safety and versatility of IR3535.
Natural repellents
Plant-derived essential oils like citronella, eucalyptus, and lavender have long been utilized as natural insect repellents. These oils include volatile molecules that either conceal the aroma of human skin or irritate mosquitos. Despite being less effective and lasting less time than synthetic repellents, some looking for natural alternatives prefer them.
How mosquito repellents work
The basic effect of mosquito repellents is to disrupt the mosquito’s sensory perception. Mosquitoes recognize humans via sensors that gather up chemical, thermal, and gaseous cues. Here’s how repellents affect certain senses:
Olfactory interference
Most repellents emit compounds that confuse mosquito olfactory receptors, preventing them from recognizing people as a food source.
Thermal disruption
Some repellents also diminish the body’s thermal signature, which mosquitoes can sense via their antennae.
Visual deterrence
Although less prevalent, certain repellents create visual disturbance to help mosquitos avoid detection.
Efficacy and duration of protection
Factors influencing efficacy
The concentration of the active ingredient, a person’s skin chemistry, and external influences are some of the variables that affect how effective insect repellents are. Higher concentrations of active chemicals often provide longer-lasting protection. However, sweating, being in the water, and the surrounding temperature can all alter how long something is effective.
Comparing different repellents
Repellents containing DEET usually offer protection for several hours; at higher dosages (20–30%), protection can continue for up to 8–10 hours. In the same quantities, picaridin offers comparable protection. Depending on the concentration, IR3535 offers 4 to 8 hours of moderate protection. Natural repellents with shorter half-lives, such as eucalyptus and citronella oils, usually last two to four hours.
The importance of mosquito repellents
Disease prevention
The most important reason to use insect repellents is disease prevention. Mosquito-borne diseases are responsible for millions of fatalities globally, particularly in tropical and subtropical areas.
Comfort and productivity
Insect repellents increase comfort and productivity by letting people enjoy outdoor activities without being bothered or disturbed by mosquitoes.
Testing and validation of mosquito repellents
To ensure the safety and efficacy of mosquito repellents, rigorous testing and validation are essential.
Efficacy testing
Efficacy test is performed to evaluate how effectively a repellent can prevent mosquito bites. This involves controlled laboratory tests and field trials.
Safety assessment
Safety assessment is performed to ensure that the repellents are safe for human use, especially for long-term application.
Performance testing
This test measures how long the repellent remains effective on the skin or clothing.
Mosquito repellent tests available at MIS
- The arm-in-cage test method is designed to evaluate the effectiveness of mosquito repellent compositions. This mosquito repellent test includes topical repellents (such as lotions, cremes, and spray formulations) as well as impregnated textiles.
- The room test is designed to evaluate the efficacy of repellent formulations in more realistic conditions while limiting volunteer exposure to mosquito-borne diseases. The “Room test” evaluates the efficacy of a repellent formulation with free-flying mosquitos in more controlled conditions in a room environment.
- Tunnel test is a laboratory assay used to measure the mortality (death) and blood feeding success of host-seeking mosquitoes on an insecticide treated material.
- Olfactometer test is a procedure used in entomology to determine the behavioral responses of mosquitos towards mosquito repellents and attractants.
At Microbe Investigations Switzerland, we provide comprehensive testing services to ensure your mosquito repellents are both effective and safe. Our team of expert microbiologists employs state-of-the-art methodologies to evaluate the efficacy of your products against mosquitoes, providing you with reliable and accurate results. Trust MIS to help you understand the science behind your repellents and enhance their marketability through rigorous testing.
To learn more about our mosquito repellent testing services or to schedule a consultation, please contact our specialists today.
