Efficacy, Safety and Biological Characteristics of Formulation Based on Essential Oil Against Co‐Infections of Herpes Simplex Virus‐1 and Candida albicans

ABSTRACT Oral coinfections involving herpes simplex virus (HSV) and Candida albicans can potentially interact and exacerbate each other. Starting from bibliographical investigation, this study aimed to examine the effectiveness of some essential oils (EOs), and their commercial formulations, both against C. albicans and HSV‐1, identifying their antimicrobial, anti‐inflammatory and allergenic potential. A preliminary review examined essential oils' efficacy against HSV‐1. Broth microdilution tested 14 EOs, a commercial formulation (LA), and a homemade one (MIX) against three fungal strains. The quality of LA, MIX and single EOs was assessed by Solid Phase Microextraction (SPME) sampling coupled with gas chromatography‐mass spectrometry (GC‐MS) analysis. To assess the allergenic activity of MIX, LA, and single EOs a Basophil Activation Test (BAT) was standardized. ELISA tests were done to evaluate the anti‐inflammatory activity. The bibliographic search highlighted seven EOs active against HSV‐1. Four EOs showing strong antifungal activity were blended, following IFRA lip‐application limits, to create a formulation (MIX) for comparison with a commercial herpes treatment (LA). Formulations were active against HSV‐1, able to modulate the expression of pro (TNF‐α LA = −29.7% and TNF‐α MIX = −33.6%) and anti‐inflammatory (IL‐1β LA = −50.0% and IL‐1β MIX = −25.0%) cytokines and no allergenic. MIX reinforces target cells and blocks viral entry, while LA also limits intracellular replication. EO‐based formulations show promise for managing HSV‐1 and Candida co‐infections, offering antiviral, antifungal, and anti‐inflammatory effects. BAT results indicate no basophil activation at tested concentrations, supporting their safety.