What effects do herbs have on pets’ health?

In the spotlight

Botanicals are attracting increased interest, not just from pet food makers in search of the new ingredients, but also from owners and veterinarians in search of a holistic approach to pet health. 

Herbs are an abundant source of ingredients with a plethora of pharmacological effects, and thus have always been in the spotlight of drug research and development. They come in numerous forms: dried, tinctures, solid and liquid extracts and fresh plant extracts, to name but a few. All of them contain hundreds of chemical ingredients, such as polyphenols, alkaloids, volatile oils, phytosterols, glycosides and many more. 

Given their complexity, the health effects of herbs will also be complex, whether systemic (respiratory, reproductive, digestive) or antimicrobial (antibacterial, antiviral, antifungal). Multimodal action and a low rate of side effects makes them often suitable for long-term use, which sometimes gives them an advantage over a single active pharmaceutical ingredient. 

For instance, when it comes to bacterial resistance development, theoretically, a mixture of antimicrobial ingredients would be more difficult for bacteria to resist. However, when used inattentively, herbs can cause toxicities like any other active substance, regardless of the origin and method of preparation. 

Does natural mean safe?

The common perception that natural products are a safer and better option than chemically synthesised drugs is not based on scientific evidence. Herbs are often variable which means that their composition changes depending on certain factors, such as humidity, temperature, soil quality (even contamination) in the area where plants are grown. They are more unstable during storage, due to the presence of enzymes. 

This means that there are important challenges to ensure quality, safety and efficacy of herbal products. A proper stabilisation and standardisation during good manufacturing practice of herbal medicinal products will mitigate these risks and optimise batch-to-batch consistency, so the health effects of the herbal product can be more predictable.  

Empirical evidence

When it comes to real efficacy of herbs in treating health problems in companion animals, there is a lack of data, and the recommended doses are mainly empirical or extracted from research on humans. Given the possible benefits of herbs and the lack of solid clinical evidence, when it comes to use of herbs in companion animals, the emphasis should be on their safety.

Some of the studied herbs with proven efficacy in dogs and cats are:

• aloe vera – used as laxative or wound healing agent, while its compound acemannan has been studied in dogs and cats for its immunostimulating properties
• andrographis – has a proven beneficial effect on heart and antiparasitic efficacy on microfilaria in dogs 
• ginger – reduced the vomiting frequency in dogs taking chemotherapeutic cisplatin. It also showed antiparasitic activity in dogs naturally infected with Dirofilaria immitis 
• ginseng – has improved liver regeneration and ameliorated liver injury in dogs 
• neem – improved the efficacy of common synthetic insect repellent DEET in reduction of flea infestation in cats and dogs, and in another study in dogs it enhanced healing of ulcers 
• milk thistle – two constituents from milk thistle, silymarin and silibinin had protective effects in dogs given toxic chemicals that specifically damage the liver 

A cautious approach

Clearly, there are many more herbs with potential health benefits in companion animals. However, a cautious approach regarding dosage and route of administration is advised. For example, the use of comfrey in small animals should be limited only to external use. Garlic can cause anemia in small animals, but this blood toxicity happens in higher doses. According to Wynn and Fougére (Veterinary Herbal Medicine, 1st ed. 2007) one clove of garlic per 20-25 kg is not toxic. 

The simple recommendation for pet owners interested in the possible benefits of herbs for their companions, but confused by scarce or contradictory information, would be to talk to a veterinarian with a background in botanical medicine in order to define how to use herbs safely and effectively. With responsible use, botanicals can be a great support in companion animal health protection.