A new study raises the concern the popular anti-wrinkle treatment Botox may travel from its injection site into the brain.

Researchers studied how a toxin found in Botox affected rats. It was injected into their whisker muscles. Three days later signs of the toxin showed up in their brains.

A California plastic surgeon says more research is needed.

"I sort of doubt that in the doses that we use, which are small and we are injecting locally, that it’s going to travel to those areas,” said plastic surgeon Dr. Edward Domanskis. “Although I have seen where you inject it into the glabellar area and you can get problems with ptosis or drooping of the lid.”

The maker of Botox says the study is inconclusive.

The FDA is looking into reports of illnesses in people of all ages who used the drugs for a variety of conditions, including at least one hospitalization of a woman given Botox for forehead wrinkles.