The direct activity of antimicrobial peptides against microbes is thought to be an essential first line of defence in the skin; however, little is known about antimicrobial peptide secretion in the skin of the external auditory canal. Evidence suggests that mast cells contribute to the secretion of antimicrobial peptides. This study aimed to examine the distribution of mast cells and antimicrobial peptides, including human β-defensin-1 and -2 and LL-37, in the external auditory canal skin.

External auditory canal skin samples from 12 patients undergoing middle-ear surgery with canaloplasty were immunohistochemically stained to detect expression of mast cell markers (tryptase and chymase) and antimicrobial peptides (human β-defensin-1 and -2 and LL-37).

Mast cells and human β-defensin-1 were present in the ceruminous glands but not in the sebaceous glands. The increased presence of mast cells, human β-defensin-1 and LL-37 in ceruminous glands suggests that mast cells may participate in the secretion of antimicrobial peptides from ceruminous glands.

These findings suggest that mast cells contribute to the secretion of antimicrobial peptides in the ceruminous glands of the external auditory canal skin.