St. John's Wort vs a Dog Calming Chew: Which One Actually Belongs in Your Cabinet

By Claire Tusch, DVM, CVA, CVMMP

✓ Medically reviewed by Claire Tusch, DVM, CVA, CVMMP — August 17, 2026 For general education — not a substitute for veterinary care.

Supplements · August 21, 2026 · 5 min read

St. John's Wort is a human antidepressant herb with real toxicity risk in dogs; it isn't a swap for a calming chew, and I wouldn't reach for it at all.

A dachshund named Pretzel taught me this one. His owner had read online that St. John’s Wort was “nature’s Xanax” and started giving him capsules from her own medicine cabinet before a move across the state, three days before the truck arrived. By the second day, Pretzel’s ears and the thin skin around his muzzle were red, and he wouldn’t stop pawing at his face after an afternoon in the yard. That’s photosensitization, and it’s the single most common reason I tell owners not to substitute a human supplement for a dog-specific calming chew. We stopped the herb, kept him indoors during peak sun for a week, and the redness resolved. It could have been worse if he’d gotten into a full bottle instead of a few loose capsules.

Do this first: don’t substitute St. John’s Wort for a calming chew. It’s not a straightforward swap, and the safety profile in dogs is different enough from the human supplement aisle that I’d skip it entirely for situational anxiety — storms, travel, fireworks, the vet visit. Here’s how the two options actually compare, and what I reach for instead.

What St. John’s Wort actually does in a dog’s body

St. John’s Wort (Hypericum perforatum) inhibits reuptake of serotonin, dopamine, norepinephrine, and glutamate — which is roughly why it’s marketed as a mood herb for people. In dogs, two things matter more than the mechanism. First, ASPCA lists Hypericum as toxic to dogs, with hypericin as the toxic principle: ingestion can cause photosensitization, meaning skin exposed to sunlight afterward can blister and ulcerate, along with vomiting, diarrhea, and lethargy. Second, because it acts on serotonin pathways, it can interact with other serotonergic medications and raise the risk of serotonin syndrome — tremors, agitation, rigidity, elevated heart rate. VCA Animal Hospitals covers the plant’s toxic effects and the sun-sensitivity risk in more detail, and it’s worth reading before you consider giving any human supplement to a dog on other medication.

None of that means every dog who licks a leaf ends up in the ER. It means the margin for error is narrow, dosing for dogs isn’t standardized, and there’s no calming-specific evidence base behind it the way there is for ingredients formulated for dogs.

What a dog-specific calming chew is built to do instead

A calming chew formulated for dogs isn’t trying to replicate a human antidepressant. It’s built around ingredients with actual behavioral research behind them, dosed for a dog’s body, without the photosensitivity or serotonin-interaction baggage. Ashwagandha is one of the better-studied ones: a systematic review of multiple randomized controlled trials found that Cureus: KSM-66 Ashwagandha has a moderate positive impact on stress reduction and cognitive performance. L-theanine, the amino acid found in tea, has been studied for its calming properties, and a research review notes a positive effect in one study on psychotic anxiety at 400 mg/day for 8 weeks — a human dose, not a canine one, so it’s directional evidence rather than a green light to self-dose. Chamomile has a longer history than a clinical record: for most species, the review literature notes, evidence is derived mainly from preclinical studies or traditional use, which is honest framing rather than a knock against it.

Boops Pets’ Calming & Stress Relief chews lean on that same ingredient set — KSM-66 Ashwagandha, L-theanine, chamomile, valerian root, ginger, magnesium, and a modest dose of melatonin — formulated specifically for dogs and third-party tested for purity and potency. It’s the option I’d point Pretzel’s owner toward for the next move: something built for the species, at a dose meant for the species, with a safety profile that doesn’t require avoiding sunlight for a week afterward.

Head-to-head: the tradeoffs, plainly stated

The honest counterargument is that some owners have used St. John’s Wort in dogs for years without incident, and a few holistic protocols still reference it. I take that seriously — anecdote isn’t nothing, and I don’t dismiss it out of hand. But “some dogs tolerated it” isn’t the same as “it’s the better tool,” and when a purpose-built, tested alternative exists at a comparable price point, the risk-reward math doesn’t favor the herb. I’d rather manipulate the routine — a predictable wind-down, a settle mat, the chew given thirty minutes before the trigger — than manipulate a human antidepressant dose down to guesswork for a 22-pound dog.

What I’d actually tell an owner standing in the aisle

I’ve had this conversation more times than the Pretzel story alone. The owners I see most often aren’t looking for a miracle; they’re looking for the dog to stop shaking under the desk when the thunder starts, or to make it through a car ride without drooling on the seats. In my practice, I start every one of those conversations the same way: what’s the trigger, how long does it last, and what’s already part of the routine. A chew is one lever, not the whole plan. If a dog is pacing at 2 a.m. every night regardless of weather or schedule, that’s a different conversation — possibly one for our melatonin guide or a vet visit to rule out pain, which is often mistaken for anxiety in older dogs with early joint changes (see our dog hip and joint supplement guide if stiffness is part of the picture).

For situational stress specifically, pair the chew with the routine: a predictable wind-down does as much as the ingredient itself. That’s not a dodge — it’s the same thing I’d say about any supplement, including the ones I formulate around. Our broader look at what’s actually in most calming chews walks through which actives have real support and which are decorative.

So which one actually goes in the cabinet

By the time an owner asks me this question, they’ve usually already ruled out the herb — the search that got them here was really “is there a safer option,” and there is. This is situational calming support, for the storm, the trip, the fireworks, not a treatment for a diagnosed anxiety disorder; if a dog’s fear responses are severe or constant, that’s a conversation with your vet, not a supplement aisle decision.

Between the two, I’d choose the dog-specific chew every time, and Boops Pets’ Calming & Stress Relief is a defensible pick on the ingredients, the dosing, and the testing. St. John’s Wort stays out of the cabinet in my house and in my recommendations. The harder question, honestly, is whether the dog needs a supplement at all, or just a quieter room and a predictable evening. Which one is it in yours?