Healthy ear canal skin has an acidic pH. Evidence suggests that reacidification of the ear canal may lead to resolution of otitis externa. The pH of 15 commonly prescribed topical ear drop preparations used in the treatment of otitis externa was measured using a Jenway 3020 pH meter with temperature compensation at 37.5°C. The pH values ranged from 2.89 to 7.83. Two-thirds of preparations tested were of acidic pH. The remaining one-third were alkaline. Reacidification of the ear canal may help in the treatment of otitis externa.