Botox is also approved for treating cervical dystonia, which is a condition that causes rigid neck muscles. Both Botox and Myobloc are derived from the botulinum toxin and work by blocking nerve impulses in the affected muscles.

Public Citizen said that it had reviewed 180 case reports submitted to the FDA by the manufacturers and found several cases of muscle weakness, difficulty swallowing or aspiration pneumonia. The latter is a dangerous condition that is caused by inhaling foreign particles into the lungs.

Of the 16 deaths alleged to have been caused by the injections, just one death was traced to the cosmetic use of Botox. The rest of the deaths were attributed to use of the injections for painful muscle conditions, but the exact causes are unknown at the moment, Public Citizen said.

“Nobody should die from the medical use of Botox,” said Dr. Sidney M. Wolfe, director of health research group at  Public Citizen. “The fact that they are shows that patients don’t have a clue about these problems.”

Allergan said in a statement that there were no safety issues "in the petition that are not already addressed in the labeling for Botox."

Public Citizen maintained that stronger warnings would benefit both doctors as well as patients, "These significantly improved warnings to doctors and patients would increase the likelihood of earlier medical intervention when symptoms of adverse reactions to botulinum toxin first appear, and could prevent more serious complications, including death," it added in a statement.

According to the National Institutes of Health, Botox is a drug made from a toxin produced by the bacterium Clostridium botulinum; the same toxin that also causes fatal food poisoning called botulism.

"Botox injections work by weakening or paralyzing certain muscles or by blocking certain nerves. The effects last about three to four months," the NIH said, adding that pregnant or breast feeding women must not use the product.