A South African game reserve has developed a treatment for rhino horns that is safe for the animals but causes convulsions and headaches to people who consume them, a wildlife group says.

The potion is a mixture of drugs used to kill parasites on the rhinos, and includes a dye that turns even finely ground horns neon pink when seen by airport scanners, Rhino and Lion Reserve spokeswoman Lorinda Hern told national news agency SAPA.

"The chemicals have the dual threat of keeping away both natural and human parasites ... and last for three to four years," she said.

The treatment has been tested on rhinos at the park outside Johannesburg, she said.

"A permanent solution would be to eliminate the demand for rhino horn altogether," Ms Hern said.