pyrethrin
noun
py·re·thrin
pī-ˈrē-thrən 
-ˈre-
-ˈre-
: either of two oily liquid esters C21H28O3 and C22H28O5 having insecticidal properties and occurring especially in the flowers of pyrethrum
Examples of pyrethrin in a Sentence
Recent Examples on the Web
Complicating matters further is the fact that lice appear to have evolved some resistance to pyrethrin and permethrin, the active ingredients in many over-the-counter lice shampoos.
—
Anna North, Vox, 7 Dec. 2018
Look for products containing ingredients such as pyrethrin, bifenthrin, or carbaryl.
—Nafeesah Allen, Better Homes & Gardens, 26 July 2024
According to the county, the pesticide is an ultra-low volume spray of pyrethrin or pyrethroids, which is approved by the Environmental Protection Agency.
—Nollyanne Delacruz, The Mercury News, 26 July 2024
Also, research shows that lice have built up resistance to many popular over-the-counter lice products that contain permethrin and pyrethrin, which are insecticides.
—Lindsey Bever, Washington Post, 28 June 2024
Look for shampoos that contain ingredients like pyrethrin or permethrin, which are known to be effective against fleas at all stages of their life cycle.
—Amber Smith, Discover Magazine, 8 Nov. 2023
Similar to permethrin lotion, pyrethrins don't kill unhatched eggs, so a second treatment is usually recommended 9 days after the first.
—USA TODAY, 16 Mar. 2024
Use them sparingly, and only if necessary; most feature pyrethrins or their synthetic version, pyrethroids.
—Brett Martin, Popular Mechanics, 17 May 2023
This seasonal favorite contains many different toxins, including pyrethrins, which can cause GI upset, drooling, vomiting, and diarrhea.
—Arricca Elin Sansone, House Beautiful, 22 Apr. 2023
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Anna North, Vox, 7 Dec. 2018
Look for products containing ingredients such as pyrethrin, bifenthrin, or carbaryl.
—Nafeesah Allen, Better Homes & Gardens, 26 July 2024
According to the county, the pesticide is an ultra-low volume spray of pyrethrin or pyrethroids, which is approved by the Environmental Protection Agency.
—Nollyanne Delacruz, The Mercury News, 26 July 2024
Also, research shows that lice have built up resistance to many popular over-the-counter lice products that contain permethrin and pyrethrin, which are insecticides.
—Lindsey Bever, Washington Post, 28 June 2024
Look for shampoos that contain ingredients like pyrethrin or permethrin, which are known to be effective against fleas at all stages of their life cycle.
—Amber Smith, Discover Magazine, 8 Nov. 2023
Similar to permethrin lotion, pyrethrins don't kill unhatched eggs, so a second treatment is usually recommended 9 days after the first.
—USA TODAY, 16 Mar. 2024
Use them sparingly, and only if necessary; most feature pyrethrins or their synthetic version, pyrethroids.
—Brett Martin, Popular Mechanics, 17 May 2023
This seasonal favorite contains many different toxins, including pyrethrins, which can cause GI upset, drooling, vomiting, and diarrhea.
—Arricca Elin Sansone, House Beautiful, 22 Apr. 2023
Dictionary Entries Near pyrethrin
Cite this Entry
“Pyrethrin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/pyrethrin. Accessed 3 Dec. 2024.
Copy CitationMedical Definition
pyrethrin
noun
py·re·thrin
pī-ˈrē-thrən
-ˈreth-rən
-ˈreth-rən
: either of two oily liquid esters C21H28O3 and C22H28O5 that have insecticidal properties and are the active components of pyrethrum
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