During the recent annual GEDAC days held last June in Ajaccio, our colleague Anne Roussel had the opportunity to update our knowledge on Phytotherapy and Aromatherapy in Veterinary Dermatology.
The increasing interest in alternative therapies in veterinary medicine, particularly in dermatology, prompts us to meticulously examine the efficacy and role of phytotherapies and aromatherapies in the treatment of canine skin conditions. First, it must be remembered that despite significant enthusiasm from dog and cat owners, the lack of rigorous, randomized, placebo-controlled clinical studies, as well as the intrinsic variability of plant extracts, constitute major limitations to an objective evaluation of their therapeutic potential. Here is an in-depth analysis of the available data, highlighting the strengths and weaknesses of current approaches and proposing recommendations for future research, to clarify the role of these therapies in veterinary clinical practice.
Definitions and Regulatory Framework
Phytotherapy, defined as the therapeutic use of plants, their extracts, and their natural active principles, aims at healing, relieving, or preventing ailments. Aromatherapy, a specific branch of phytotherapy, exploits the therapeutic properties of essential oils, concentrated volatile compounds extracted from different parts of plants (flowers, leaves, bark, roots, etc.). These essential oils, administered topically (local skin applications), orally (ingestion), or as an aerosol (inhalation), benefit from significant enthusiasm in human and veterinary medicine, fueled by the perception of a more “natural” alternative to conventional treatments. However, it is crucial to emphasize that the scientific basis supporting the efficacy and safety of many applications remains fragile, despite a long tradition of use in traditional medicine.
The World Health Organization (WHO) lists over 22,000 medicinal plants used in traditional medicine worldwide. However, only a few thousand have been the subject of in-depth scientific studies respecting the rigorous methodological standards necessary to establish proof of efficacy and safety. This significant difference between traditional use and scientific validation poses a major challenge for the integration of phytotherapy into modern medical practice.
In human medicine, phytotherapeutic drugs generally require a Marketing Authorization (MA), issued by a competent regulatory agency (such as the National Agency for the Safety of Medicines and Health Products – ANSM in France). However, the very nature of the MA for phytotherapeutic products is often different from that of synthetic drugs. Full clinical trials are not always mandatory, and approval often relies on a long tradition of use and pharmacological and toxicological data, rather than large-scale clinical studies demonstrating superiority over a placebo.
In veterinary medicine, obtaining a Marketing Authorization (MA) for phytotherapeutic drugs appears to be a major obstacle to the development of this type of treatment. The high costs associated with rigorous clinical studies and stricter regulatory requirements than in humans are often prohibitive for pharmaceutical companies. This phenomenon favors the use of food supplements, which are less regulated and therefore less subject to quality and efficacy controls.
Nevertheless, in the face of growing concerns about antibiotic resistance, initiatives such as the Ecoantibio 2 Plan (in France) have favored the easing of MA requirements for veterinary phytotherapeutic drugs, especially those based on well-established use for at least ten years. This measure aims to encourage the exploration of alternatives to antibiotics, but it does not fully resolve the problem of rigorous scientific validation of these treatments.
Application of Phytotherapy in Canine Dermatology
Transposing data from human dermatological research to veterinary applications poses serious challenges. Physiological and pharmacokinetic differences between humans and dogs complicate the extrapolation of results. A systematic review of the scientific literature, such as that by Tresch et al. (2019), evaluated the effectiveness of four medicinal plants (Calendula officinalis, Hypericum perforatum, Matricaria chamomilla, and Salvia officinalis) in the treatment of various canine dermatological conditions, such as pyoderma, atopic dermatitis, otitis externa, wounds, and dermatophytosis.
These plants have demonstrated broad-spectrum antibacterial and antifungal properties in vitro, including activity against antibiotic-resistant bacteria. Calendula, St. John’s wort, and chamomile have shown wound-healing and anti-inflammatory properties; chamomile notably possesses soothing properties. In vitro studies have also highlighted the antimicrobial activity of pomegranate extract against Malassezia pachydermatis and Staphylococcus pseudintermedius, two pathogens frequently involved in canine dermatoses.
However, the interpretation of these in vitro results and their extrapolation to clinical applications in dogs require the utmost caution. The wide disparity of studies (over 8295 publications according to Tresch et al., 2019), their generally poor methodological quality, and the difficulty of standardizing plant extracts make the evaluation of clinical efficacy complex. The chemical composition and concentration of active principles vary considerably depending on the geographical origin of the plants, cultivation conditions, extraction methods, and storage. This variability makes it difficult to reproduce results and limits the reliability of conclusions. It is therefore crucial to develop standardization methods to ensure the quality and reproducibility of extracts used in research and clinical practice.
Aromatherapy and its Role in the Treatment of Skin Infections
Aromatherapy, with the use of essential oils, offers interesting prospects, particularly in the treatment of skin infections. Numerous in vitro studies have demonstrated the antimicrobial activity of various essential oils against bacteria and fungi responsible for dermatological infections in dogs.
Manuka essential oil (Leptospermum scoparium), for example, shows remarkable activity against Staphylococcus pseudintermedius, including methicillin-resistant strains (MRSP), and even inhibits the formation of bacterial biofilms. Commercial preparations containing Manuka essential oil, combined with essential fatty acids and antiseptic compounds, have demonstrated clinical efficacy in the treatment of pyoderma, in synergy with antibiotic treatments, allowing a reduction in the duration and dose of antibiotics needed, thus decreasing the risks of antimicrobial resistance.
Tea tree essential oil (Melaleuca alternifolia) also possesses antimicrobial potential, but it is crucial not to confuse it with Manuka essential oil. In vitro studies have compared the antimicrobial activity of several essential oils on S. pseudintermedius. Cinnamon essential oil (Cinnamomum zeylanicum) has distinguished itself by its low minimum inhibitory concentration (MIC), demonstrating powerful bactericidal activity. The growing interest in conducting aromatograms in some veterinary laboratories opens the way for a personalized approach in the choice of essential oils based on the sensitivity profile of bacteria isolated from each patient.
A comparison of the antimicrobial activity of honey and essential oils revealed that honey, in some cases, exhibits lower MICs than certain essential oils, notably Manuka essential oil and propolis. This observation highlights the need to compare different therapeutic approaches and determine the most effective protocols depending on each pathology and context.
Stimulation of Antimicrobial Peptide Synthesis: An Interesting Mechanism of Action
In vitro studies have shown that certain plant extracts, such as Peumus boldus and Spiraea ulmaria, stimulate the production of antimicrobial peptides (AMPs). These peptides, naturally produced by skin keratinocytes and sebocytes, play a crucial role in innate immunity by disintegrating bacterial membranes and recruiting inflammatory cells. The non-specific action of AMPs makes them effective against a wide spectrum of bacteria, including S. pseudintermedius (SPSM and SPRM), Gram-negative bacteria, and Malassezia pachydermatis. This stimulation of the innate immune response by plant extracts represents a promising mechanism of action for the treatment of skin infections.
Discussion and Perspectives: Research Needs and Challenges to Overcome
Current data regarding the efficacy of phytotherapies and aromatherapies in canine veterinary dermatology are limited by the crucial lack of controlled, randomized, blinded clinical studies in dogs. Most information comes from in vitro studies or clinical studies conducted in humans, whose extrapolation to dogs must be extremely cautious due to physiological and metabolic differences. The intrinsic variability of plant extracts, already mentioned, represents another major challenge.
To guide practitioners in their therapeutic choices, rigorous clinical studies, conducted with standardized plant extracts and following precise administration protocols, are imperatively needed. The precise identification and quantification of bioactive compounds in these extracts will allow for a more precise and reproducible approach. The evaluation of the pharmacokinetics and pharmacodynamics of phytotherapeutic and aromatherapeutic compounds in dogs is also indispensable to optimize their use.
A more precise analysis of the mechanisms of action would allow for a refined selection of the most effective plants and essential oils for each canine dermatological condition. In particular, studying the interactions between active plant compounds and the various components of the cutaneous immune system could open up novel perspectives in the development of more targeted and effective treatments. The use of biomarkers could also contribute to a better assessment of therapeutic efficacy and a better understanding of patient response to different therapies.
Conclusion
The use of phytotherapy and aromatherapy in canine veterinary dermatology remains promising but requires much more robust scientific validation. Future research must focus on conducting large-scale, randomized, placebo-controlled, blinded clinical trials, using standardized, controlled, and precisely quantified plant extracts, with reproducible extraction methods and precise administration protocols.
It is important to emphasize the need for a multidisciplinary approach, integrating expertise in botany, chemistry, pharmacology, and veterinary clinics to ensure the reliability of results. In-depth studies on the pharmacokinetics and pharmacodynamics of active compounds in dogs are essential to define optimal doses and minimize the risk of toxicity.
It is also essential to consider potential interactions between phytotherapeutic or aromatherapeutic products and conventional allopathic treatments. An integrated approach, combining conventional therapies and natural approaches, should be considered with caution and under the strict supervision of an experienced veterinarian with solid knowledge of medicinal plants and their interactions. This integrated approach will allow for the best possible use of both types of treatments and provide optimal care for canine patients.
FAQ
1. What are the main limitations of current studies on phytotherapy and aromatherapy in veterinary dermatology?
The main limitations are the lack of controlled, randomized, and blinded clinical studies in dogs, the variability of plant extracts, the difficulty in standardizing extraction and preparation methods, and the unjustified extrapolation of human data. Furthermore, most studies lack rigorous statistical analysis and clear, objective evaluation criteria.
2. How can the quality and standardization of plant extracts used in research be guaranteed?
Rigorous methods of cultivation, extraction, and analysis of bioactive compounds are necessary to guarantee the quality and consistency of the extracts. The implementation of quality standards (for example, by following ISO standards) and the traceability of products, from cultivation to final formulation, are essential. The use of high-performance liquid chromatography (HPLC) and mass spectrometry (MS) to quantify bioactive compounds is a crucial step in the standardization of extracts.
3. What are the next steps for a better scientific evaluation of these alternative therapies?
The priority is to conduct randomized, placebo-controlled, blinded clinical trials, with large control groups and standardized dosages. The identification of specific biomarkers to monitor disease progression and treatment response will also be of great help in evaluating efficacy. Collaboration between clinicians, researchers, chemists, and botanists will allow for a more rigorous methodological approach.
4. Is there a risk of toxicity associated with the use of medicinal plants and essential oils in dogs?
Yes, there is a risk of toxicity, particularly in cases of overdose or inappropriate use in fragile or young animals. Some plants may interact with other medications. Careful administration, adhering to appropriate doses and a precise protocol, under the strict supervision of a veterinarian, is imperative. It is crucial to consult a veterinary toxicology reference before using any medicinal plants or essential oils in dogs. It is also vital to determine the long-term effects of exposure to active compounds.
5. How can the use of a phytotherapeutic or aromatherapeutic approach be reconciled with conventional treatment?
An integrated approach, combining conventional treatments and natural approaches, should be considered with caution and under the supervision of a veterinarian. A thorough understanding of possible interactions between allopathic drugs and plant active principles (synergistic or antagonistic effects) is imperative to avoid the risks of adverse effects or reduced therapeutic efficacy. Communication between the owner and the veterinarian is essential to ensure optimal patient care.
References:
Tresch M, Mevissen M, Ayrle H, Melzig M, Roosje P, Walkenhorst M. Medicinal plants as therapeutic options for topical treatment in canine dermatology? A systematic review. BMC Vet Res. 2019 May 27;15(1):174. (and other references mentioned in the original text)
