Mechanism of Action
Chamomile's best studied calming compound is apigenin. In preclinical research published in Planta Medica in 1995, apigenin was identified as a ligand at the benzodiazepine binding site of GABA-A receptors, the receptor system through which the brain's main inhibitory messenger works, with anxiety-reducing effects in laboratory animals. Chamomile also contains other flavonoids and oils that may contribute.
Evidence Summary
The strongest clinical evidence is human. A 2009 randomised double-blind placebo-controlled trial by Amsterdam and colleagues in the Journal of Clinical Psychopharmacology found a pharmaceutical-grade chamomile extract reduced generalised anxiety symptoms significantly more than placebo over eight weeks, in a small group. The same team extended the work with a longer-term trial published in Phytomedicine in 2016.
In dogs the position is simpler: no controlled canine anxiety trials of chamomile have been published. Its place in a dog supplement rests on traditional use, the characterised mechanism and human findings at human doses. That is worth stating exactly because a small trial in people using a standardised extract is not evidence about your dog.
In Petz Park Products
Stress + Anxiety for Dogs contains 60mg of chamomile per scoop, from $34.95 AUD for 45 scoops up to $99.95 AUD for 180, rated 4.7 stars from 590 reviews. Stress + Anxiety for Cats contains 15mg of chamomile extract per scoop, $32.95 AUD for 60 scoops or $58.95 AUD for 120, rated 4.7 stars from 235 reviews.
Safety and Considerations
Chamomile is in the daisy (Asteraceae) family and animals or people sensitised to related plants such as ragweed or marigolds are more likely to react to it. Human references also note possible interactions with warfarin and some liver-metabolised drugs, plus a theoretical additive effect with sedatives. Problems at pet supplement doses are uncommon but stop and see your vet if you notice skin irritation, vomiting or unusual drowsiness. The dog formula also contains St John's Wort which interacts with many medications, so check with your vet if your dog takes any medication.