The Food and Drug Administration issued a warning on Friday regarding the possible side effects of Botulinum toxin injections, which in some cases have been linked to the death of approximately 16 people, four of which occurred in children, and the development of serious conditions for 164 people.

In the Friday announcement, the FDA linked the reactions with what appeared to be a form of botulism, which is a rather rare, but serious illness, caused by the botulin toxin, leading to respiratory and muscular paralysis. The Food and Drug Administration’s review focused on Botox, Botox Cosmetic (Botulinum toxin Type A) and Myobloc (Botulinum toxin type B), all of them sold in the United States.

The investigation started after several patients were hospitalized after receiving a cosmetic treatment with one of the products; however, a direct link between the injections and the side effects has not been established so far. The Public Citizen Health Research Group, an organization defending the consumers’ interests, has forwarded a petition to the FDA asking to begin an investigation and start issuing warning on the possible adverse reactions.

Sidney Wolfe, director of the Public Citizen Health Research, released a statement on Friday, saying: “Our analysis of FDA data found that between Nov. 1, 1997, and Dec. 31, 2006, the makers of the drugs had reported 180 U.S. cases of people developing serious conditions after receiving injections.”

Russell Kratz, director of the neurology products division at the Center for Drug Evaluation and Research belonging to the FDA, said however that it is very unlikely that the drugs were responsible for the cases of severe illnesses developed in some patients, and that in most cases the injections were used for non-neuromuscular disorders, which is the possible reason for triggering side effects.

According to Kratz, dozens of patients have been injected with the Botulinum toxin at the recommendation of their doctor, which is perfectly fine if the physician believes they are appropriate. Such off-label treatments have been used for some time now for patients who declared they’ve had absolutely no side effects. The FDA will continue to investigate the matter.