Efficacy of common reagents for killing ticks in the ear canal

OBJECTIVE: To determine if widely available solutions can effectively kill ticks that may be found in the human ear canal. METHODS: This study was prospective, controlled and blinded animal study. Lone star ticks (Amblyomma americanum), both nymphal and adult, were submerged in one of four preparations (acetone, isopropyl alcohol 70%, ethanol 95%, or 4% lidocaine) in test tubes (n = 20 per group) for 20 minutes. Ticks were agitated by intermittent probing. Activity of the nymphal ticks was directly observed while those of the adult ticks was video‐recorded during the exposure period. Two blinded investigators viewed the videos of adult ticks and during the exposure period to determine the time until death (ie, movement cessation). Mortality was assessed immediately after exposure, and confirmed 24 and 48 hours after exposure. RESULTS: Acetone killed ticks most rapidly (nymph mean time = 185.1 s; adult mean time = 562.9 s). Isopropyl alcohol 70% (nymphs, 328.9 s; adults, 1128.4 s) and ethanol 95% (nymphs, 294 s; adults, 1129.4 s) took longer to kill the ticks. All ticks treated with 4% lidocaine survived. These differences were significant (nymphs, P < .0001; adults, P < .0001). CONCLUSIONS: Acetone was the fastest acting and most effective reagent, followed by ethanol and isopropyl alcohol. These solutions may prove useful in otoacariasis with an intact tympanic membrane. LEVEL OF EVIDENCE: N/A