A Psychological Guide to Upper Face Botulinum Toxin Injections: Baseline Emotional Functions of Facial Expressions

The upper face is central to human nonverbal communication, with the glabellar complex, forehead, and lateral canthal area signaling core emotions such as anger, sadness, fear, surprise, and joy. Botulinum toxin type A (BoNT-A) is widely used to modulate muscle activity in these regions, not only reducing dynamic wrinkles but also affecting emotional expression and perception.

The aim of this narrative review is to synthesize psychological and neurobiological insights into a region-focused framework, helping clinicians incorporate emotional considerations into BoNT-A treatments of the upper face.

A narrative literature review was conducted using PubMed and Scopus, combining the search terms "botulinum toxin", "facial expression", "emotion", "mimicry" and "psychology". Peer-reviewed articles addressing facial Action Units (AUs), neural mechanisms, or psychological outcomes were included. Citation tracking and the authors' clinical expertise further informed the synthesis.

The upper face is integral to various facial expressions, with each region contributing distinct signals relevant to intrapersonal experience and interpersonal communication. BoNT-A can alter these facial expressions, with potential benefits such as mood enhancement, but also possible limitations in conveying authenticity. While neuroimaging and behavioral findings support links between facial feedback and limbic activity, systematic data on region-specific psychological outcomes remains scarce.

Understanding baseline emotional functions of facial expressions is crucial for clinicians, as these movements shape intrapersonal experience and interpersonal communication. Integrating this knowledge into counseling enables transparent, well-informed discussions before BoNT-A application. Future research should systematically evaluate expressive flexibility and patient-reported satisfaction with emotional communication.