Picaridin

Effectiveness

Picaridin and DEET are the most effective insect repellents available. A 2018 systematic review found no consistent performance difference between picaridin and DEET in field studies and concluded that they are equally preferred mosquito repellents, noting that 50% DEET offers longer protection but is not available in some countries.

Picaridin has been reported to be as effective as DEET at a 20% concentration without the irritation associated with DEET. According to the WHO, picaridin "demonstrates excellent repellent properties comparable to, and often superior to, those of the standard DEET".

Picaridin-based products have been evaluated by Consumer Reports in 2016 as among the most effective insect repellents when used at a 20% concentration. Picaridin was earlier reported to be effective by Consumer Reports (7% solution) and the Australian Army (20% solution). Consumer Reports retests in 2006 gave as result that a 7% solution of picaridin offered little or no protection against Aedes mosquitoes (vector of dengue fever) and a protection time of about 2.5 hours against Culex (vector of West Nile virus), while a 15% solution was good for about one hour against Aedes and 4.8 hours against Culex.

The United States Centers for Disease Control and Prevention recommends using repellents based on picaridin, DEET, ethyl butylacetylaminopropionate (IR3535), or oil of lemon eucalyptus (containing p-menthane-3,8-diol, PMD) for effective protection against mosquitoes that carry the West Nile virus, eastern equine encephalitis and other illnesses.

Adverse effects

Picaridin can cause mild to moderate eye irritation on contact and is slightly toxic if ingested.

Environmental impact

A 2018 study found that a commercial repellent product containing 20% picaridin, in what the authors described as "conservative exposure doses", is highly toxic to larval salamanders, a major predator of mosquito larvae. The study observed high larval salamander mortality occurring delayed after the four days of exposure. Because the widely used LC50 test for assessing a chemical's environmental toxicity is based on mortality within four days, the authors suggested that picaridin would be incorrectly deemed as "safe" under the test protocol. However, picaridin was also non-toxic in a 21-day reproduction test on the water flea Daphnia magna and a 32-day early life-stage test in zebrafish.

Since only the picaridin content of the tested repellent product is known, the observed effects cannot be readily attributed to picaridin. Furthermore, the effects of the repellent product showed no dose-response relationship, i.e., there was neither an increase of the magnitude or severity of the observed effects (mortality, tail deformation), nor did the effects occur at earlier time points. The study has been regarded as invalid by the Danish Environmental Protection Agency, which has evaluated picaridin prior to its approval under the EU Biocidal Product Regulation. The reasons for rejection were the testing of a mixture of undisclosed composition, the use of a non-standard test organism, the lack of analytical verification of actual test concentrations, and the fact that the test solution was never renewed with the 25 days of study duration.

Mechanism of action

In 2014, a potential odorant receptor for picaridin (and DEET), CquiOR136•CquiOrco, was suggested for Culex quinquefasciatus mosquito.

Recent crystal and solution studies showed that picaridin binds to Anopheles gambiae odorant binding protein 1 (AgamOBP1). The crystal structure of AgamOBP1•picaridin complex (PDB: 5EL2) revealed that picaridin binds to the DEET-binding site in two distinct orientations and also to a second binding site (sIC-binding site) located at the C-terminal region of the AgamOBP1.

Research on Anopheles coluzzii mosquitoes suggests picaridin does not strongly activate their olfactory receptor neurons, but instead reduces the volatility of the odorants with which it is mixed. By reducing their volatility, picaridin effectively "masks" odorants attractive to mosquitoes on the skin, preventing them from reaching the olfactory receptors to some extent.

Chemistry

Picaridin contains two stereocenters: one where the hydroxyethyl chain attaches to the ring, and one where the sec-butyl attaches to the oxygen of the carbamate. The commercial material contains a mixture of all four stereoisomers.

Commercial products

Commercial products containing picaridin include Cutter Advanced, Muskol, Repeltec, Skin So Soft Bug Guard Plus, Sawyer Picaridin Insect Repellent, Off! FamilyCare, Autan, Smidge, PiActive and MOK.O.

References

References

1. "Picaridin".
2. (5 April 2010). "Efficacy Test of KBR 3023 (Picaridin; Icaridin) - Based Personal Insect Repellents (20% Cream and 20% Spray) with Ticks Under Laboratory Conditions". LANXESS Corporation.
3. [https://web.archive.org/web/20110809050453/http://www.picaridin.com/science.htm Picaridin]. Archived from [http://www.picaridin.com/science.htm the original] on August 9, 2011.
4. (4 August 2023). "Picaridin vs DEET: Which Is the Best Insect Repellent?". Appalachian Mountain Club.
5. (2 January 2016). "Percutaneous penetration and pharmacodynamics: Wash-in and wash-off of sunscreen and insect repellent". Journal of Dermatological Treatment.
6. "Picaridin Technical Fact Sheet".
7. (31 January 2005). "Bayer Completes Spin Off of Lanxess AG".
8. [http://cen.acs.org/articles/86/i20/Saltigo-Renames-Insect-Repellant.html Saltigo renames insect repellant], [[Chemical & Engineering News]]
9. (2013). "Travel Medicine".
10. "Commission Implementing Regulation (EU) 2020/1086 of 23 July 2020 approving icaridin as an existing active substance for use in biocidal products of product-type 19.".
11. (May 2018). "Mosquito repellents for the traveller: does picaridin provide longer protection than DEET?". Journal of Travel Medicine.
12. (2004). "Picaridin: a new insect repellent". Journal of Drugs in Dermatology.
13. (December 2014). "Field evaluation of picaridin repellents reveals differences in repellent sensitivity between Southeast Asian vectors of malaria and arboviruses". PLOS Neglected Tropical Diseases.
14. (30 May 2018). "Mosquito Repellents That Best Protect Against Zika". [[Consumer Reports]], April, 2016.
15. [https://web.archive.org/web/20080201140313/https://www.consumerreports.org/cro/cu-press-room/pressroom/archive/2005/07/eng0507det.htm?resultPageIndex=2&resultIndex=15&searchTerm=mosquito - Consumer Reports Confirms Effectiveness Of New Alternative To Deet] (link recreated from Wayback Machine Internet Archive – 19 May 2019)
16. (May 2004). "Field evaluation of repellent formulations containing deet and picaridin against mosquitoes in Northern Territory, Australia". Journal of Medical Entomology.
17. "Insect repellents: which keep bugs at bay?" ''Consumer Reports'', June 2006, vol 71 (issue 6), p. 6.
18. "Traveler's Health: Avoid bug bites". [[Centers for Disease Control and Prevention]].
19. (March 2009). "Picaridin Technical Fact Sheet". National Pesticide Information Center.
20. (October 2018). "High mortality in aquatic predators of mosquito larvae caused by exposure to insect repellent". Biology Letters.
21. (31 October 2018). "Widely used mosquito repellent proves lethal to larval salamanders". ScienceDaily.
22. "ECHA - Information on biocides".
23. "ECHA - Information on biocides.".
24. "ECHA - Information on biocides".
25. (10 December 2019). "Opinion on the application for approval of the active substance Icaridin, Product type: 19.".
26. (November 2014). "Mosquito odorant receptor for DEET and methyl jasmonate". Proceedings of the National Academy of Sciences of the United States of America.
27. (January 2017). "The crystal structure of the AgamOBP1•Icaridin complex reveals alternative binding modes and stereo-selective repellent recognition". Cellular and Molecular Life Sciences.
28. (November 2019). "Commonly Used Insect Repellents Hide Human Odors from Anopheles Mosquitoes". Current Biology.
29. "Insect Repellent Solutions | Repeltec | AFFIX Labs | Finland".
30. Cha, Ariana Eunjung. "[https://www.proquest.com/docview/1761035571/ Zika virus FAQ: What is it, and what are the risks as it spreads?] ''The Washington Post''. January 21, 2016.