Melissa officinalis (Lemon balm)

What Is Melissa officinalis (Lemon Balm)?

Melissa officinalis, commonly known as lemon balm, is a perennial herb in the Lamiaceae (mint) family native to southern Europe and western Asia. It has been used in traditional medicine for centuries primarily for its calming, sleep-promoting, and digestive properties in humans. It has recently attracted scientific attention for potential anxiolytic effects in companion animals.

The herb's bioactive profile is complex. Its leaves contain a mixture of phenolic acids, flavonoids, and volatile oils, the most pharmacologically studied of which is rosmarinic acid (RA), a polyphenol with documented antioxidant and GABAergic properties. Additional bioactive constituents include caffeic acid, protocatechuic acid, flavonoids (quercitin, rhamnocitrin, luteolin), and volatile oils including citral and citronellal. (Roy et al., 2025)

This chemical complexity is both lemon balm's strength and one of the key reasons its mechanism of action in dogs remains incompletely characterized, the whole extract may exert effects that neither rosmarinic acid alone nor any other single compound fully accounts for.

How Lemon Balm May Work: The Proposed Mechanisms

Melissa officinalis is thought to exert its calming effects through at least three partially overlapping mechanisms, each targeting a different component of the central nervous system's stress and anxiety response.

GABAergic modulation via rosmarinic acid

The primary and best-characterized mechanism involves the GABA system - the central nervous system's chief inhibitory neurotransmitter network. Rosmarinic acid, the principal active compound in lemon balm extract, inhibits the enzyme GABA-transaminase (GABA-T), which is responsible for breaking down GABA after it has been released into the synapse. By slowing this degradation process, rosmarinic acid increases the availability of GABA in the brain, prolonging and enhancing the inhibitory signal that GABA provides. The net effect is an increase in the brain's inhibitory tone, which may translate clinically to reduced neuronal excitability, anxiolytic activity, and calmer behavior. (Roy et al., 2025)

This mechanism is supported by metabolomic data: in the only published canine study to date, dogs supplemented with lemon balm extract showed a measurable decrease in 4-hydroxybutyric acid (GHB), a direct metabolite of GABA, compared to placebo controls. This biochemical shift is consistent with reduced GABA breakdown and increased GABAergic activity, the proposed mechanism operating at the molecular level, measurable in blood. (Roy et al., 2025)

Cholinergic system modulation

In addition to GABAergic effects, the volatile oils in lemon balm, particularly citral and citronellal, are thought to interact with muscarinic and nicotinic acetylcholine receptors in the brain. The cholinergic system plays a complex role in arousal, attention, and stress reactivity. By modulating receptor activity at these sites, lemon balm volatile oils may help dampen the physiological "fight-or-flight" arousal response, contributing to the herb's overall calming profile through a pathway distinct from its GABAergic effects. (Roy et al., 2025)

HPA axis suppression

Melissa officinalis is also thought to modulate the hypothalamic-pituitary-adrenal (HPA) axis, the body's primary stress response system, which governs cortisol release. By suppressing HPA overactivation, lemon balm may reduce the sustained physiological stress response that contributes to chronic anxiety, fear-based behaviors, and arousal states in dogs. This mechanism is consistent with the broader literature on lemon balm's anxiolytic effects in humans and other species, though it has not yet been directly quantified in canine studies. (Roy et al., 2025)

The whole-extract vs. isolated compound question

A key finding from the one published dog study is that the full Melissa officinalis extract outperformed isolated rosmarinic acid at a dose equivalent to the RA content of the full extract. This suggests that the complete phytochemical profile of lemon balm, including flavonoids, additional phenolic acids, and volatile oils, contributes to its calming effect through mechanisms beyond rosmarinic acid alone. The synergistic or additive contributions of these compounds remain an active area of investigation. (Roy et al., 2025)

The Clinical Evidence: What the One Published Dog Study Shows

The entire evidence base for Melissa officinalis in dogs currently rests on a single published study. This is essential context for any clinical interpretation of the available data.

Roy et al. (2025), published in BMC Veterinary Research, conducted a randomized four-arm study in 20 healthy adult Beagle dogs at Oniris (the National Veterinary School of Nantes, France). Dogs were allocated to one of four groups (5 dogs per group): placebo (maltodextrose 200 mg/kg daily), a commercial hydroalcoholic Melissa officinalis extract (MOE, 200 mg/kg daily), isolated rosmarinic acid (10.6 mg/kg daily — the equivalent dose of RA present within the MOE), or alpha-casozepine (225 mg Zylkene daily), which served as the active reference comparator given its established evidence base. All supplementation continued for four weeks. (Roy et al., 2025)

Behavioral assessment was conducted using a standardized evaluation grid developed by Oniris, with a novel object test (a yellow trash can the dogs had never previously encountered) used as the mild stress paradigm. Observers evaluated behavioral responses in a standardized enclosure.

Results were notable. Mean behavioral score differences relative to baseline showed a striking separation between groups: the placebo group scored -3.4, reflecting behaviorally detectable stress in response to the novel object, while the MOE group scored +2.0, the rosmarinic acid group +1.4, and the alpha-casozepine reference group +0.8. The lemon balm extract produced the largest behavioral improvement — outperforming not only placebo but also the established reference supplement alpha-casozepine on this measure. (Roy et al., 2025)

Metabolomic findings reinforced the behavioral data. GHB levels decreased in all supplemented groups compared to the placebo group, consistent with increased GABA availability. The untargeted metabolomic analysis revealed that MOE supplementation produced distinct changes in lipid and bile acid metabolism pathways, while rosmarinic acid alone primarily affected fatty acid and lipid metabolism, suggesting the full extract activates metabolic pathways that isolated RA does not. (Roy et al., 2025)

Safety markers — including liver enzymes (ALT, ALP, AST), renal function (creatinine, urea), and complete blood counts, showed no adverse changes in any supplemented group across the four-week period, suggesting acceptable short-term safety at the doses studied. (Roy et al., 2025)

Critical Limitations: Why One Study Is Not Enough

The results are genuinely interesting, but several limitations prevent these findings from serving as the basis for firm clinical recommendations.

Sample size is extremely small. Five dogs per group is insufficient to draw statistically robust conclusions, calculate meaningful confidence intervals, or control for individual variation. A dog that happened to be naturally calmer or more reactive in a given group could substantially skew the group mean. Any finding from a study of this size should be treated as hypothesis-generating, not confirmatory.

The study used healthy dogs exposed to mild stress, not clinically anxious patients. Dogs with genuine anxiety disorders, separation-related behaviors, or noise phobias may respond very differently than healthy laboratory Beagles encountering a novel object in a controlled enclosure. The gap between a stress response to an unfamiliar object and clinical separation anxiety is clinically significant.

Potential industry involvement. The commercial lemon balm extract used in the study (Nor-balm) is manufactured by Nor-Feed SAS, a company that appears affiliated with some of the study authors. Industry-affiliated research is not automatically invalid — but it warrants increased scrutiny of the study design, outcome selection, and interpretation.

This is the only published canine study. The broader human and rodent literature on Melissa officinalis is more developed, but direct translation from human or laboratory animal research to clinical veterinary application is not reliable, particularly for behavioral outcomes.

What the Evidence Supports and What It Doesn't

Based on the current published literature, the following positions are defensible:

Melissa officinalis has a biologically plausible mechanism of action: rosmarinic acid's inhibition of GABA-T is pharmacologically coherent, and the metabolomic evidence from Roy et al. 2025 demonstrates measurable downstream GABAergic effects in dogs. The behavioral improvement over alpha-casozepine in the one published study is an encouraging signal that warrants further investigation.

What the evidence does not yet support is a clinical recommendation for use in dogs with anxiety disorders. A single study of five dogs per group, conducted in healthy animals under mild stress conditions, with potential industry involvement, is insufficient to make evidence-based prescribing or supplement recommendations. The clinical effect size and durability in anxious client-owned dogs is entirely unknown.

Practical Guidance for Owners

If you are considering lemon balm for a dog with anxiety or stress-related behavior, the following principles apply:

• Consult your veterinarian first. Anxiety in dogs has multiple causes and presentations. A behavioral assessment is the appropriate starting point before any supplement is trialed.
• Understand the evidence ceiling. One small study in healthy dogs is not the same as clinical trial evidence in anxious dogs. Expect uncertainty, not certainty.
• If used, choose a standardized extract. The Roy et al. study used a commercial hydroalcoholic extract standardized to a defined rosmarinic acid content. Unstandardized dried herb products will have highly variable active compound concentrations.
• Monitor behavioral response systematically. The caregiver placebo effect is well-documented in veterinary behavioral research. Tracking behavior with a simple validated rating scale before and after supplementation is the only reliable way to determine whether an individual dog is actually responding.
• Do not use as a substitute for behavioral medicine in dogs with severe anxiety. For dogs with clinically significant separation anxiety, noise phobias, or aggression, pharmacological behavioral medicine combined with structured behavioral modification remains the evidence-based standard of care.

Final Thoughts 

Melissa officinalis has an interesting and increasingly well-characterized mechanism of action, a favorable short-term safety profile at the doses studied, and one genuinely intriguing published canine study showing behavioral improvements that exceeded those of an established reference supplement. That is a more encouraging starting position than many herbal supplements bring to veterinary medicine.

What it does not yet have is the repeated studies, sufficient sample sizes, the clinical population validity, or the independent research base needed to support evidence-based recommendations. PetEvidenceProject will update this review as further controlled trials in client-owned dogs with anxiety disorders become available. Until then, Melissa officinalis sits in the same category as SAMe for cognition: a supplement with a plausible mechanism, an early positive signal, and a genuine need for better data before firm clinical conclusions can be drawn.