Calming treats for dogs: what the ingredients actually do

The honest answer is: a little, sometimes, for some ingredients, in some situations. Merck, the standard veterinary reference, says evidence for natural products in dogs is somewhat limited, while noting a calming effect has been observed with alpha-casozepine and that diets with tryptophan and casozepine might help decrease stress. (Merck)

L-theanine for dogs

L-theanine is one of the most common calming ingredients, yet a search of PubMed found no controlled study of it for anxiety in dogs. The only pet trial listed was in 33 cats, with no placebo group. We are not saying it does not work, only that we could not find the trials that would show it does. (Dramard 2018, Merck)

L-tryptophan

Tryptophan is the raw material for serotonin, so the idea is sound, but the results are mixed. In 36 dogs fed added tryptophan for 24 weeks, behaviour towards familiar and unfamiliar people did not differ consistently from dogs on the control diet. An older crossover study in 33 dogs found lower territorial aggression on one supplemented diet. A 2024 evidence review concluded tryptophan is not enough as a sole treatment. (Templeman 2018, DeNapoli 2000, Sofyan 2024)

Alpha-casozepine

This milk protein has the most direct test. In a randomised placebo-controlled trial, dogs given casozepine for two days before a vet examination had lower stress scores and lower pulse rates than dogs on placebo. But cortisol rose in the treated dogs, dogs in both groups stayed excited, and the authors called the effect weak. (Schroers 2024)

Melatonin for dog anxiety

The ASPCA notes melatonin is sometimes used for separation anxiety in dogs, but we found no controlled study of melatonin alone for anxiety behaviour. The one controlled dog study we found, in 14 puppies, measured pulse, breathing and blood markers during road transport, not anxiety. (ASPCA, Uchendu 2022)

Chamomile, valerian and passionflower

We found no controlled dog study of chamomile at all, or of valerian or passionflower on their own. A randomised double-blind trial in 44 dogs tested a blend of tryptophan, valerian and passionflower given for some time before New Year’s Eve, and found a greater fall in fireworks fear than placebo. Because it was a blend, it cannot tell you which ingredient helped, and the maker paid for the study. (Ramos 2024)

Probiotics

The gut is a newer target. One randomised placebo-controlled trial in 40 dogs reported better owner-rated anxiety and aggression scores after 4 weeks on a single probiotic strain. The maker funded the trial and helped design it, and a result for one strain does not carry over to other probiotics. (Bijaoui 2025)

CBD has more dog trials than any other calming ingredient, and they disagree. In studies run by a pet food company, a single dose eased some stress measures in 40 dogs left alone or taken in a car, and daily CBD over six months reduced cortisol, whining and lip licking in 19 dogs during car travel at one or more time points. (Hunt 2023, Flint 2024)

Other trials found nothing. In 16 dogs played a fireworks noise, CBD treats did not lower cortisol or change behaviour, while a prescription anxiety medicine did lower cortisol; the authors said the results do not support an anti-anxiety effect. A trial of 20 dogs found no behavioural difference from a control oil. (Morris 2020, Marliani 2024)

Is CBD legal for dogs?

In the US, the FDA has not approved cannabis, including CBD, for any use in animals, and says it cannot ensure the safety or effectiveness of these products. It has also concluded that adding CBD or THC to any food, including animal food, is prohibited in interstate commerce. The FDA cautions pet owners against these products and recommends talking with your vet about treatment options. (FDA)

• When the FDA tested CBD products, many did not contain the levels of CBD they claimed. (FDA)
• Some CBD products also contain THC, which can make dogs very sleepy and unsteady. (ASPCA)
• A systematic review of 22 articles found no serious adverse events reported, but said long-term safety and optimal dosing remain unclear. (Moreno-López 2025)

We also tried to read the American Veterinary Medical Association’s pages on cannabis and pets, but they would not load for us, so this section relies on the FDA.

Most calming ingredients carry no specific poisoning warning in Merck or ASPCA pages. The danger is usually something else on the label, or a product made for people. (Merck, ASPCA)

Too much of an otherwise safe ingredient can still cause trouble: an overdose of melatonin can cause vomiting, lethargy, sedation and wobbliness. Keep calming chews out of reach like any medicine, because dogs will happily eat a whole tub of something tasty. (Merck)

A treat might take the edge off a car ride. It will not fix fear that has a pattern. Merck is clear that even prescribed medicine works by making learning possible, and that lasting change needs behaviour modification. The plan should be reward-based: AVSAB’s position is that only reward-based methods should be used for all dog training, and it does not support shock, prong or choke collars. (Merck, AVSAB)

Signs that your dog needs a plan rather than a product:

• Fear or panic that happens again and again, or is getting worse. Start with our dog anxiety guide to work out the type. (Merck)
• Distress only when left alone: barking, damage at exits or toileting. See separation anxiety in dogs for a graduated departure plan. (Merck)
• A sudden change in behaviour, or signs of pain or illness, which vets must rule out first. (Merck, VCA)
• Fear that could lead to a bite, or aggression of any kind. (Merck, VCA)

For a one-off event such as a storm or a vet visit, our guide on how to calm an anxious dog gives a before, during and after checklist, and our page on the dog anxiety vest covers what the studies found on pressure wraps. Merck notes that several studies support pheromone therapy, a firmer statement than it makes about calming supplements. (Merck)

If a treat is not enough, your vet may talk about prescription medicine, some of which is FDA-approved for specific anxiety problems in dogs. These are the classes Merck lists for fear and anxiety in dogs. We give no names of products and no doses: your vet may discuss these only after examining your dog, and always as part of a behaviour plan. (Merck)

• Selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), which Merck names as core classes for fear, anxiety and aggression. (Merck)
• Situational medicines given before a known trigger, such as alpha-2 agonists, trazodone, clonidine and gabapentin. One oral alpha-2 agonist gel is FDA-approved for noise aversion in dogs. (Merck)
• Benzodiazepines, which Merck describes as powerful anti-anxiety drugs to be prescribed with caution. (Merck)
• Buspirone, sometimes added to an SSRI or TCA. (Merck)

Merck also notes that two medicines are FDA-approved for separation anxiety in dogs when used with a behaviour modification plan. Tell your vet about any calming treat you are giving, because several of these medicines act on serotonin, as do tryptophan and 5-HTP. (Merck, Merck)

Start with your own vet. Behaviour changes can come from pain or illness, which a vet must rule out before anything else, and your vet can prescribe medicine and refer you on. (Merck, VCA)

A veterinary behaviourist is a vet who has gone on to complete an internship, a residency of 3 to 5 years and a board examination, and is certified by the American College of Veterinary Behaviorists (ACVB). They can diagnose medical problems that affect behaviour, prescribe anti-anxiety medicine and design a behaviour plan, working with your own vet. (VCA)

You can search for a board-certified veterinary behaviourist on the ACVB’s own site, dacvb.org, or ask your vet for a referral.

Every figure and threshold on this page comes from the veterinary sources below, and each one is linked where it is used. Where no source gives a cut-off, we say call your vet rather than invent one.