The body's national medication control officer, Dr Warwick Vale, said there was a risk such products might contained a prohibited substance.
He advised members, horse trainers, owners, exhibitors, riders and their veterinarians to apply caution in using herbal or natural medicinal preparations, tonics, pastes, powders, and products of any kind because of the risk they might contain a banned substance.
"The classification of many of these substances as prohibited is neither a new policy nor a recent development," he said.
"Herbal and natural medicinal products are classified as prohibited because of their potential actions on various body systems when administered."
Herbal or natural medicine preparations include those used either intravenously, topically, intramuscularly, beneath the skin or orally, and products where the ingredients and their quantitative analysis are not specifically known.
"This advice should also be applied to the use of homeopathic remedies," he said.
"Persons responsible should be aware that ingredients labelling for such preparations is often not complete or accurate.
"This is especially true of those products containing plant ingredients. The plant origin of any herbal or natural medicine ingredient does not preclude it from containing a pharmacologically potent and readily detectable prohibited substance."
Some examples of the hundreds and perhaps thousands of herbal/natural or plant ingredients that would cause a product to be classified as prohibited are: valerian, kava, passionflower, skullcap, chamomile, vervain, lemon balm, leopard's bane, night shade, capsaicin, comfrey, devil's claw, hops, laurel, lavender, red poppy, and rauwolfia, not to mention tea, coffee, chocolate and Coca-Cola!
Many prohibited substances have their origin in plants, he said, such as salicylates, digitalis, reserpine, caffeine and atropine.
"Especially problematic are preparations that are claimed to calm or relax while at the same time being said to contain no prohibited substances," Dr Vale said.
"The use of any herbal or natural product to affect the performance of a horse in a calming (tranquillising) or an energising (stimulant) manner is expressly prohibited by the FEI and EA anti-doping rules.
"The use of a calming product during competition may also have important safety consequences."
Dr Vale said herbs and plant extracts are also marketed as horse feed supplements.
"Many herb products are marketed as sedatives. While many herbs are generally regarded as safe to feed to horses, there is a scarcity of independent scientific data in horses on the safety and efficacy of most herbal products and supplements. Most of the information available on these products is anecdotal."
In addition, he said, the levels of the natural constituents in herbs can vary greatly as a result of the parts of the plant harvested, the growth stage of the plant at harvest, and the processing methods.
"Herbs may also contain chemicals that can be harmful, such as certain alkaloids. Toxicities have been associated with comfrey and chaparral in humans, and horsetail and snakeroot are known to be toxic to horses."
He said horse owners should be most careful about any claims by manufacturers or others that their preparations are "legal" or permissible for use at competitions recognised by Equestrian Australian or the FEI.
"The FEI and EA do not test or approve herbal or natural products to verify a possible violation of the FEI/EA anti-doping rules. Therefore, a claim that the product does not violate FEI/EA rules or is undetectable by drug testing is the sole responsibility of the manufacturer or individual making such a claim."
Persons administering herbal or natural product could ultimately find themselves misled by such claims, he said.
"Although the use of some of these products may not have resulted in adverse analytical findings from medication control tests in the past, this may change as the FEI/EA Drug Testing and Research Laboratories incorporate new methods into their battery of screening tests," he said.
"This is a deliberate and ongoing process.
"The analytical techniques used in the testing laboratory are becoming more refined, and the fact that these products have not been detected by testing in the past does not hold any guarantee for their safe use in competition.
"It is important to note that many herbal products that are produced for the equine market routinely have their formulations changed without any published notice.
"It is for this reason that Equestrian Australia typically does not comment on products by name, but requests lists of ingredients. It would be irresponsible for the EA to list or name the brand of products as prohibited or permitted as there is often no control or notification of changes in their ingredients."
He said Equestrian Australia "cautions most strongly" against any use of herbal and natural products and products, for which the ingredients and properties are not known, in competition horses.
"The doping of horses is against the policies of EA and the FEI.
"Doping is contrary to the spirit of sport. The use of a herbal or natural medicine product in a competition horse is implicitly associated with a desire to affect or improve the normal competition performance of the horse.
"This desire is at odds with the FEI and EA code of conduct and core values relating to horse welfare and the spirit of the sport."