There is a call for a "black box" warning on a popular anti-wrinkle procedure.

Researchers at the consumer group Public Citizen said Botox should carry a black box warning. They reviewed adverse event reports submitted to the FDA and found 16 deaths have been reported. The manufacturer of Botox said these risks are already listed on the drug label.

Botox is famous for smoothing facial wrinkles, but has also been approved for treating rigid neck muscles.

Researchers at the consumer group Public Citizen said the botulinum tox spreads inside the body causing serious problems.

The report detailed cases of muscle weakness, difficulty swallowing or aspiration pneumonia, a serious condition caused by breathing a foreign material into the lungs.

Officials at Allergan, Solstice and the FDA could not immediately be reached for comment.