Irritant contact keratitis caused by the bodily fluids of a brown marmorated stink bug

PURPOSE: The brown marmorated stink bug is native to Asia (China, Taiwan, Japan, and the Korean peninsula). Its bodily fluids are toxic and irritating to the human skin and eyes. Human case reports are rare. Only one report of irritant contact dermatitis has been published. We report a case of irritant contact keratitis resulting from the chemical components of the bodily fluids of the bug. MATERIALS AND METHODS: A case report. RESULTS: A 74-year-old male presented to our emergency department with pain and redness in his right eye, which had been exposed to the bodily fluids of a brown marmorated stink bug. A patch of central corneal epithelial defect with conjunctival congestion and chemosis was found in his right eye. His best-corrected visual acuity (BCVA) (OD) was 6/20. We prescribed topical antibiotic and lubricant medications. The corneal epithelial defect recovered gradually over the course of several days. BCVA worsened to 2/60 but recovered gradually to 6/8.6 after the epithelial defect healed and after use of topical steroid for suppression of the local inflammation. DISCUSSION: The adult brown marmorated stink bug is characterized by its shield shape and its dark, mottled, brown color. The stink bug ranges in length from 14 to 17 mm. A startled stink bug will react by biting or spraying a foul-smelling liquid from its thorax. When disturbed or crushed, the stink bug excretes a highly potent, odorous smell. The major component of the bodily fluids is trans-2-decenal and trans-2-octenal, chemicals that belong to the aldehyde group. Hydrogen ions (H(+)) produced by reduction and oxidation of aldehyde can induce chemical burn injuries to the ocular surface. Irritant contact keratitis may occur through this mechanism. CONCLUSION: Stink bugs excrete odorous bodily fluids as a defensive mechanism when threatened. If the toxic fluid gets into the human eye, it can cause unexpected chemical burns or injury. Patients whose eyes come into contact with these bodily fluids should rinse their eyes thoroughly and immediately seek medical attention.