chemistry

Insect repellent

Insect repellent is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Insect repellent rather than just read about it. In short: An insect repellent (also commonly called "bug spray" or "bug deterrent") is a substance applied to the skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and control the outbreak of insect-borne (and other arthropod-borne) diseases such as malaria, Lyme disease, dengue fever, bubonic plague, river blindness, an…

Key takeaways

Insect repellent belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Insect repellent to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Insect repellent from memory before moving on to harder problems.

Reference excerpt

An insect repellent (also commonly called "bug spray" or "bug deterrent") is a substance applied to the skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and control the outbreak of insect-borne (and other arthropod-borne) diseases such as malaria, Lyme disease, dengue fever, bubonic plague, river blindness, and West Nile fever. Pest animals commonly serving as vectors for disease include insects such as flea, fly, and mosquito; and arachnids such as ticks . Some insect repellents are insecticides (bug killers), but most simply discourage insects and send them flying or crawling away.

Effectiveness Synthetic repellents tend to be more effective and/or longer lasting than "natural" repellents. For protection against ticks and mosquito bites, the U.S. Centers for Disease Control (CDC) recommends DEET, icaridin (picaridin, KBR 3023), oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), IR3535 and 2-undecanone with the caveat that higher percentages of the active ingredient provide longer protection. In 2015, researchers at New Mexico State University tested 10 commercially available products for their effectiveness at repelling mosquitoes. The known active ingredients tested included DEET (at various concentrations), geraniol, p-menthane-3-8-diol (found in lemon eucalyptus oil), thiamine, and several oils (soybean, rosemary, cinnamon, lemongrass, citronella, and lemon eucalyptus). Two of the products tested were fragrances where the active ingredients were unknown. On the mosquito Aedes aegypti, only one repellent that did not contain DEET had a strong effect for the duration of the 240 minutes test: a lemon eucalyptus oil repellent. However, Victoria's Secret Bombshell, a perfume not advertised as an insect repellent, performed effectively during the first 120 minutes after application. In one comparative study from 2004, IR3535 was as effective or better than DEET in protection against Aedes aegypti and Culex quinquefasciatus mosquitoes. Other sources (official publications of the associations of German physicians as well as of German druggists) suggest the contrary and state DEET is still the most efficient substance available and the substance of choice for stays in malaria regions, while IR3535 has little effect. However, some plant-based repellents may provide effective relief as well. Essential oil repellents can be short-lived in their effectiveness. A test of various insect repellents by an independent consumer organization found that repellents containing DEET or icaridin are more effective than repellents with "natural" active ingredients. All the synthetics gave almost 100% repellency for the first 2 hours, where the natural repellent products were most effective for the first 30 to 60 minutes, and required reapplication to be effective over several hours. Although highly toxic to cats, permethrin is recommended as protection against mosquitoes for clothing, gear, or bed nets. In an earlier report, the CDC found oil of lemon eucalyptus to be more effective than other plant-based treatments, with a similar effectiveness to low concentrations of DEET. However, a 2006 published study found in both cage and field studies that a product containing 40% oil of lemon eucalyptus was just as effective as products containing high concentrations of DEET. Research has also found that neem oil is mosquito repellent for up to 12 hours. Citronella oil's mosquito repellency has also been verified by research, including effectiveness in repelling Aedes aegypti, but requires reapplication after 30 to 60 minutes. There are also products available based on sound production, particularly ultrasound (inaudibly high-frequency sounds) which purport to be insect repellents. However, these electronic devices have been shown to be ineffective based on studies done by the United States Environmental Protection Agency and many universities.

Safety issues

For humans

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Insect repellent

Start with the simplest possible case. Write down what Insect repellent claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Insect repellent before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Insect repellent ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Insect repellent

In research: Insect repellent appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Insect repellent in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Insect repellent is common in secondary-school and first-year university syllabi. It links to neighbouring topics Australian inventions, Chemical ecology, Hiking equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Insect repellent outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Insect repellent in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Insect repellent means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Insect repellent out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Insect repellent in simple terms?

Why does Insect repellent matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Insect repellent?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Insect repellent.