LAUSR

BACKGROUND Acute inflammatory reactions (AIRs) are a rare complication following aesthetic treatment with hyaluronic acid (HA) and/or human collagen fillers. However, a substantial increase in the frequency of AIRs was observed in the first author's clinic since May 2020. AIMS To report AIR cases we experienced and discuss potential underlying mechanisms. METHODS This was a retrospective review of patients representing AIR symptoms following filler injection with HA or human collagen in our clinic. RESULTS Although only one case of an AIR with the incidence rate of 0.01 % was recorded following filler treatment between September 2008 and April 2020 in our clinic, we observed 14 AIR cases without anaphylaxis, with an incidence rate of 1.18 % between May 2020 and June 2021, in line with the spreading of the new coronavirus pandemic. All cases were females aged 40-57 years, and the time of onset was within hours after filler injection. Three patients had been treated with HA fillers only, 2 with HA plus human collagen, and 9 with human collagen only. Most patients had been treated with these products in the past. Nine patients were treated with oral prednisolone. In all cases, symptoms resolved entirely within a week without sequelae. CONCLUSIONS The marked increase in AIRs coincided with the COVID-19 pandemic. Possible explanations include immune system alterations caused by extensive changes in domestic and personal hygiene, prolonged and elevated stress levels, and subclinical COVID-19 infection. Further studies may be warranted.