I have been following the research literature investigating the use of pheromones to manage behavior problems in dogs and cats since my first post of the subject in 2010. Here is a rough timeline of my conclusions over that period:
2010- Pheromone Therapy for Dogs and Cats: What’s the Evidence?
“The limitations in the quality of the evidence mean we cannot definitively declare that pheromone therapy doesn’t work. What we can say is that based on the best evidence to date, it does not appear to have a benefit. Further study is certainly reasonable, but as always I question the wisdom and the ethics of widespread sale and use of products which, despite years of testing, don’t seem to have much evidence that they work.“
2010- Does the Pheromone DAP Reduce Stress in Dogs Having Surgery?
“It is possible that purified or synthetic pheromones may ultimately have a role to play in treating behavioral problems in dogs and cats, or in otherwise ameliorating the stresses associated with illness and medical care. But the products currently on the market, and widely used, have so far not done a very impressive job of proving their value. Harmless? Probably. But also perfect candidate for placebo-by-proxy effects, making owners and veterinarians feel better rather than our patients.”
2016-Evidence Update: Pheromone Therapy for Stress in Cats
“The results were pretty clear. While the clinic environment is generally more stressful than the home (reflected in differences in heart rate and respiratory rate), cats tolerate being handled and restrained in an unfamiliar environment better than in their own home (reflected in behavioral differences). In neither environment did the pheromone make any difference in the cats’ responses compared with placebo. The authors concluded that the pheromone had no influence on the markers of stress evaluated in this study.
Given the consistency of results across a number of studies, it is pretty clear at this point that pheromone products are unlikely to have any beneficial effects for dogs and cats.”
2017- Evidence Update: Feline Facial Pheromone Doesn’t Reduce Stress or URIs in Shelter Cat Study
“The findings, however, were pretty consistently negative. No difference was seen in stress scores or in the occurrence of URI between cats exposed to the pheromone and those exposed to the placebo. No evidence of harm from the pheromone treatment was seen, though this was not specifically sought.
As usual, no single study should be taken as the definitive answer to any medical question. However, in light of the fact that pheromones have been in use and studied extensively for decades and strong, consistent evidence of significant benefits has not been seen, this study strengthens the argument that these products do not, in fact, provide such benefits.”
2018-Pheromone’s Therapeutic Use in Animals
“It is clear that pheromones play an important role in the regulation of mammalian behavior, so it is plausible that they might have therapeutic value in managing problematic or pathologic behaviors. However, there is little published preclinical evidence on the composition or effects of natural pheromones or synthetic analogues, and what is available comes from proprietary or commercial sources.
Results of clinical studies of these products are mixed. Consistent, replicable evidence of clinically significant effects is not available. No evidence of any harm from pheromone products has been published, and while adverse events seem unlikely, no study has been conducted specifically to look for them.
Available pheromone products are likely safe, but it is unclear what, if any, clinical benefits they may provide for any of the variety of indications for which they are commonly recommended.”
All in all, the evidence for clinical use of pheromones in dogs and cats has not strengthened significantly in the last decade. A new study has been published which purports to support one benefit for dog and cat pheromones, but as is all too common in veterinary research, it has a critical flaw that renders its conclusions unreliable.
Prior MR, Mills DS. Cats vs. Dogs: The Efficacy of Feliway FriendsTM and AdaptilTM Products in Multispecies Homes.Front Vet Sci. 2020;7:399. doi:10.3389/fvets.2020.00399
This study looked at the potential use of both dog and cat commercial pheromone products in reducing undesirable behaviors and promoting desirable ones in households with dogs and cats living together. The authors created a list of such behaviors and a survey instrument for owners to rate their view of the relationship between their dogs and cats. The study then recruited owners, online and through veterinary practices, who felt that there was room for improvement in the relationship between their dogs and cats to test the effects of dog and cat pheromone diffusers.
The owners spent two weeks scoring the behaviors between their dogs and cats. They were then randomly assigned a diffuser emitting either a cat pheromone or a dog pheromone, and they continued scoring these behaviors for an additional four weeks. The owners and investigators didn’t know which type of diffuser each group was using. The results showed a significant increase in desirable behaviors and a significant decrease in undesirable behaviors between the baseline and test period for both pheromones, with no difference between the dog and cat products.
Have you spotted the flaw yet? That’s right, there was no placebo control. Both groups got what they believed to be a device to improve their pets’ behaviors, and both groups saw such improvement. This is the perfect design for eliciting a caregiver placebo effect, but it is not a reliable way of testing the efficacy of a behavioral treatment.
This omission of a routine, standard aspect to any clinical trial is so glaring, it would be hard to imagine the investigators didn’t deliberately choose to omit it. Certainly, the authors were aware that this design could simply be an illustration of a placebo effect, because they address the issue in their discussion:
“There are two obvious possible interpretations of the absence of a significant difference between the treatment groups in these outcomes: either both groups were subject to a similar placebo effect; or both diffuser products were similarly effective.“
Unfortunately, their response to this problem is unconvincing. They choose to simply assert, without evidence, that the effect seen was too large to be explained by placebo effects. There was also some suggestion in the data that cats responded more to cat pheromone and dogs more to dog pheromone, which the authors also feel argues against the results being due to placebo effects. However, these post-hoc explanations are just speculation, and it is mystifying that the authors would choose not to include the most basic bias control technique for any clinical study.
Bias, of course, is always an issue in any research study, which is why controls such as placebo groups and blinding are so critical. This study had several potential sources of bias beyond the cognitive biases that could have led to an owner placebo effect. The company selling the products tested had some financial relationship to the study, providing their products for free and paying for the study to be made available as an open-access publication. One of the authors, Dr. Mills, has been a committed advocate of pheromone therapy for many years. While I don’t doubt this is based on his sincere believe in the scientific case for these products, it is well-established that research groups consistently pursuing validation of a particular hypothesis tend to have deep unconscious and conscious biases in favor of that hypothesis. Research from such sources merits careful critical appraisal, particularly when essential bias control tools are not employed.
This study, unfortunately, does little to clarify the potential value of dog and cat pheromones for behavior problems due to the glaring lack of a placebo group and other potential sources of uncontrolled bias. It is disappointing that despite decades of commercial sale and clinical use of pheromone products, we are still lacking robust, replicated, convincing scientific evidence of their effectiveness.
While there are likely no direct risks to using such products, I see numerous pet owners and veterinarians turn to them before pursuing appropriate behavioral or pharmacologic therapy for serious behavioral problems. The false impression that these are treatments with solid scientific support does cause indirect harm by delaying or replacing other therapies. Our pets deserve the best treatment possible, and this is always the treatment supported by the strongest evidence. So far, pheromones do not meet this standard.