You have probably used an insect repellent at some point in your life, or wish that you had. Bites from insects such as mosquitoes, biting flies, deer flies, black flies and sand flies leave a small lump on the skin and can cause discomfort and itching. Bites and stings are naturally red, swollen, itchy and uncomfortable; of course, each insect leaves a different size/shape/colour of bite. But occasionally the bite an become infected, cause a severe allergic reaction (anaphylaxis) or spread serious illnesses.
Have you ever thought about what is inside insect repellents and how they work? This is a poster that I made about what attracts insects to humans in the first place; what is in insect repellents; and potential future developments in the industry.
What I didn’t touch on in the poster was what insects actually do when they bite you. When they first land on your skin, they make a small hole in the skin. Most bite as a form of defence, and they therefore inject venom into the person. This venom is a liquid blend of biologically active substances, usually including toxins. Toxins damage enzymes and thus undermine countless bodily functions—inhibiting the production of hemoglobin in the blood, for example. Thus, they result in the immune response which causes the swelling that we see. Many insects bite to feed on blood (proboscis), such as mosquitoes. They feed on our blood for the protein and iron in our blood which is used to make eggs, which is why only female mosquitoes bite. In the process of feeding, the mosquito injects some of its own saliva, which contains an anticoagulant that prevents your blood from clotting around the proboscis and trapping the insect. Your immune system recognizes the proteins in the mosquito’s saliva as a foreign substance and releases histamine as part of the immune response. Histamine causes itching which you may have experienced. When bites break the skin, the bacteria that live on the surface of your skin can then enter those small puncture points and develop into an infection, or you may have an allergic reaction to one of the substances in the venom. These two things cause worsened effects from bites.
But, the worst effects from bites come from diseases which the insects transmit to us. For example, malaria, which is caused by he Plasmodium parasite is mainly spread by female Anopheles mosquitoes (only live in certain areas), which mainly bite at dusk and at night. When an infected mosquito bites a human, it passes the parasites into the bloodstream. Another transmitted disease is lyme disease. To contract Lyme disease, an infected deer tick must bite you. The bacteria enter your skin through the bite and eventually make their way into your bloodstream. Zika, dengue and chikungunya viruses are transmitted to people primarily through the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus).
Therefore, if possible, I recommend that you use insect repellent.