A well-known side effect of Botox is the inability to fully express emotions. Now research reveals another side effect: the inability to fully feel emotions.

Botox, a popular cosmetic injection used to fight facial wrinkles, is made of an extremely toxic protein called Botulinum toxin. Botox works by temporarily paralyzing muscles that cause wrinkles.

Scientists think that facial expressions themselves may influence emotional experiences, so a person with a limited ability to make facial expressions may also have a limited ability to feel emotions.

“With Botox, a person can respond otherwise normally to an emotional event, [such as] a sad movie scene, but will have less movement in the facial muscles that have been injected, and therefore less feedback to the brain about such facial expressivity,” said researchers. “It thus allows for a test of whether facial expressions and the sensory feedback from them to the brain can influence our emotions.”

With Botox, looking good and feeling less.