Pet owners should seek the advice of a vet before paying for alternative therapy, according to the British Veterinary Association (BVA).
Dogs can be treated with homeopathy and acupuncture
It says the therapies, popular for dogs and horses, are often used to treat skin and joint problems.
But the BVA warns that some animals can be misdiagnosed and owners could be "throwing their money down the drain".
Niki Senior, an "animal healer" for 25 years, says there are a lot of therapists "doing good work".
The BVA is concerned that pet owners who do not consult a vet before seeking alternative treatment could prolong the suffering of their pet.
Nicky Paull, president-elect of the BVA, said that in the worst cases, animals had been diagnosed by an alternative therapist speaking to the owner on the phone. She said some had been asked to supply hair samples.
She said: "I'm a scientist. I believe in evidence-based medicine... some important problems can be missed."
Ms Senior insisted that she would not treat an animal without a vet's recommendation.
"There are lots of charlatans out there, but there are a lot of people doing good," she said.
She specialises in reiki, spiritual healing and crystal healing, treating horses, hamsters and gerbils.
Among the successes she cites is a horse whose tumour reduced in size following treatment.
Chronic back pain
She has also worked with rescued battery hens.
"[After] two treatments, the chickens which had hands-on, and crystal, healing, had their feathers grow back more rapidly than the chickens which didn't have any form of healing.
"It was quite astounding actually."
The BVA said some of its vets did work with alternative treatments, mainly homeopathy and acupuncture, and they were able to refer their clients to the therapists.
"It's quite rare for us to be approached, but there are people who look directly for alternative treatments," says Ms Paull.
She has experienced one case where a dog had been suffering chronic back pain, but was not initially seen by a vet.
It later emerged that the animal had a more serious condition and she said it had suffered unnecessarily.
The BVA advises pet owners, who have bypassed their vet, to report any problems with alternative therapists to trading standards officers.
It adds that alternative therapists are not regulated, and only a qualified vet can legally diagnose health problems in animals.