Pain is processed and experienced differently on the left (L) and right (R) sides of the body; however, L/R pain asymmetry with cosmetic treatments of the face has not been evaluated.

The authors compared patient ratings of L/R facial pain during and immediately after injectable cosmetic treatments.

In this cross-sectional multicenter pragmatic study, pain levels were evaluated for 302 patients who underwent facial treatments with botulinum toxin (BTX) and/or impermanent soft-tissue filler (STF). Patients indicated pain intensity on each side of the face with a visual analogue scale (VAS; 0, no pain; 10, worst pain).

Combined mean VAS scores for BTX and STF treatments (L, 3.79 vs R, 3.42), and individual scores for BTX (L, 3.60 vs R, 3.30) or STF (L, 4.22 vs R, 3.69) treatments were significantly different, with pain rated as worse on the L side of the face (all P < 0.01). When treatments were performed first on the L side, patients rated the overall experience as significantly less painful than when treatments were begun on the R side. BTX treatments with a 29-gauge (G) needle were significantly more painful than with a 33-G needle.

To lessen pain with injectable facial treatments, the authors recommend placing the first injection on the L side of the face and, when possible, employing a high-G needle.