Change of external auditory canal pH in acute otitis externa

We investigated (1) the correlation between the degree of acute otitis externa (AOE) and a change of pH and (2) the recovery of pH after acidification compared to an antibiotic otic solution in AOE. A change of pH in the external auditory canal (EAC) is very important for the pathogenesis of otitis externa. Therefore, not only an antibiotic otic solution, but also acidification, is known to be a good treatment for AOE. However, pH has only been investigated in chronic otitis externa, and not in AOE.

This was a prospective randomized control study. Forty adult patients (56 ears) with AOE and 40 normal control subjects (80 ears) participated in this study. The severity of disease was graded as mild, moderate, or severe. The pH of each EAC was then measured. The patients were randomly assigned into 2 groups: one for vinegar irrigation and the other for topical antibiotics. The pH of the diseased ears was measured at 1 and 2 weeks after the treatment.

The mean (+/-SD) pH for the normal control subjects was 5.4 +/- 0.48, and the EAC lost its acidity proportionately to the degree of disease (p < 0.05). For both the vinegar irrigation and topical antibiotic groups, the acidity was restored dramatically (p < 0.05) at 1 and 2 weeks for the moderate and severe grades of otitis, but not for the mild grade. There was no difference in recovery between the 2 groups.

The EAC lost its acidity proportionately to the degree of disease in AOE. Vinegar irrigation and topical antibiotics were equally effective for restoration of pH.