1.  How does Citriodiol® work? What is its mode of action?

Female mosquitoes and other biting insects are attracted to humans and other animals by a combination of CO2, heat and odour. While the mode of action of insect repellents generally is not well understood, research indicates that repellents disrupt the odour receptors on biting insects and prevent them from landing on the skin.



2.  What insects is it effective against?

Studies have shown Citriodiol® to be effective against the following species of insect and parasites:

  • Mosquitoes

  • Ticks

  • Midges

  • Horse Flies

  • Sand Flies

  • Head Lice

For more information about the species and the relevant viruses and diseases, please click here, or view our summary sheet by clicking here.



3.  Is it effective against leeches?

Citriodiol® is very effective in repelling land leeches. There is published data to support this and which can be made available to support a product claim.  We do not have data on water leeches.

We are keen to understand and promote the repellence properties of Citriodiol® so if you decide to conduct efficacy testing of your own, we’d welcome the opportunity to review your results or even to comment on the proposed study protocol in advance.



4.  Can it be used on animals such as horses?

As part of our development programme, Citrefine has begun to generate efficacy data for use of Citriodiol® based products as a repellent on horses. The results are promising and we will be continuing this work. 

We have not yet prepared internal risk assessments as to the safe use of Citriodiol® on horses; however, it has been used at low concentrations on horses in Europe for at least a decade. In addition, our consulting toxicologist with full access to our acute toxicity, repeat dose toxicity and teratogenicity (developmental) studies is of the professional opinion that we can readily support a bridging argument and risk assessment for higher concentration formulations applied to horses. 

If you are interested in more information on horses or in a product for other animals please contact us.



 5.  How else can Citriodiol® be used?

The data on Citriodiol® supports the use of the active substance against a range of biting insects and other arthropods in a dermally applied personal repellent. Citriodiol® is used in other applications, such as application to horses to repel insects or to human hair to repel lice.  While these specific uses are not included in the EU dossier, US EPA or Canadian PMRA registrations, customers are able to support these uses by developing appropriate risk assessments and efficacy data for inclusion within their product authorisation dossiers or national registrations. 

If you have questions about how to use Citriodiol® in other applications please contact us.



6.  Is it as effective as DEET?

Comparing PMD content to DEET content in similar concentrations, independent entomologists have stated the efficacy of these substances is reasonably similar.   See, for example, Carroll 2006, Trigg 1994. Our own internal testing shows efficacy results to be similar where comparable amounts of DEET and PMD are contained in the product. This is supported by a recent independent study by the US Consumer Reports testing the Citriodiol®-based product, Repel Lemon Eucalyptus and finding 30% formulations on par with DEET at between 7 and 8 hours of efficacy against Aedes and Culex mosquitoes and deer ticks.



7.  Is efficacy related to PMD content?

Yes, the PMD content is the principle factor in predicting the efficacy of a product. It evaporates slowly from the skin, and it is while it is in this vapour phase that it has a repellent effect.

It is worth noting that PMD, when applied in conjunction with the other naturally occurring constituents in the starting material (Eucalyptus citriodora), is substantially more repellent to biting insects than pure PMD.  Therefore it is more accurate to say that it is the Citriodiol® content of a product that determines efficacy. 



8.  What % active do you need to claim how many hours of efficacy?

Efficacy is impacted to a reasonable degree by the co-formulants in the product.  For example, lotions tend to have a slightly improved efficacy over a spray, and sprays incorporating a co-formulant that acts to slow down the rate of evaporation of the PMD (a fixative) may have longer protection times over those without.  In addition, efficacy times are affected by application rates, environmental conditions such as biting pressure, and by the target species.

With this said, if we look at the simplest formulations applied in field conditions, you might expect to be able to support a claim of complete protection for 6 hours with a 30% product (or up to 8 hours complete protection if the authority will allow this phrasing).



9.  Can it be used as a spatial repellent or in other products not applied to the skin?

In theory, yes, but it will depend on the delivery system. 

We have a large body of data supporting its safety as well as its efficacy. However, the efficacy data we have is based on dermally applied products, mainly for use on humans and not spatial repellency. While it may be possible to produce a spatial repellent product, we are not able to advise on the percentage of Citriodiol® required, or its efficacy.



10.  Can it be impregnated in material?

Citriodiol® has been successfully micro-encapsulated by several different companies and in this form can be used to impregnate fabric and clothing. Please contact us for further information.



Learn more in the FAQs section


Let's explore working together

Read next