Rare but serious side effects can result when soft tissue fillers are unintentionally injected into blood vessels in the face, according to a press release from the Food and Drug Administration.

Blood vessels can be blocked and blood flow restricted following unintentional soft tissue filler injection. The injection material can also migrate and embolization may cause vision impairment, blindness, stroke, and skin necrosis. Some injection sites result in blood vessel blockage more often, including the glabella and the periorbital region, though blockage can occur at any site on the face.

The FDA recommends that only people with appropriate training and knowledge of injection areas deliver injections, and that patients understand the risk beforehand and potential symptoms afterwards. A full list of recommendations can be found on the FDA website.

“FDA is working with manufacturers to update their labeling. The request asks that the labeling include additional warnings, precautions, and other statements about the risk of unintentional injection into blood vessels, consistent with the recommendations in this communication, so that both health care providers and patients would have a better understanding of the risks,” the FDA said.

Find the full press release on the FDA website.