Penta has been used as a fungicide, molluscicide, insecticide, and as a wood preservative, but its registrations for these purposes have gradually been cancelled over the years. It is currently registered only for industrial purposes; agricultural and domestic uses are prohibited.

Penta is intensely irritating to the skin and mucous membranes. Animals fed in troughs made of lumber treated with penta may salivate and have irritated mucous membranes of the mouth. Vaporization or leaching of penta in pens, enclosures, homes, and barns has caused illness and death. Signs of poisoning include nervousness, rapid pulse and breathing, weakness, muscle tremors, fever, convulsions, and death. Longterm poisoning results in fatty liver, kidney damage, and weight loss. Pentachlorophenol is considered to cause cancer and must be handled very carefully.

Blood tests for penta may aid in the diagnosis of poisoning, but diagnosis is usually made based on signs and treated lumber in the animal's environment.

There is no known antidote. Treatment includes removing the animal from the source of exposure, bathing animals that had skin exposure, administering activated charcoal by mouth, and providing supportive treatment, including cooling the animal and administering fluids, electrolytes (salts), and anticonvulsants. Bathing should be done gently with cold water and detergent.

Last full review/revision July 2011 by Barry R. Blakley, DVM, PhD; Cheryl L. Waldner, DVM, PhD; Rob Bildfell, DVM, MSc, DACVP; William D. Black, MSc, DVM, PhD; Herman J. Boermans, DVM, MSc, PhD; Cecil F. Brownie, DVM, PhD, DABVT, DABT, DABFE, DABFM, FACFEI; Raymond Cahill-Morasco, MS, DVM; Keith A. Clark, DVM, PhD; Gregory F. Grauer, DVM, MS, DACVIM; Sharon M. Gwaltney-Brant, DVM, PhD, DABVT, DABT; Larry G. Hansen, PhD; Safdar A. Khan, DVM, MS, PhD, DABVT; Garrick C. M. Latch, MASc, PhD; Gavin L. Meerdink, DVM, DABVT; Lisa A. Murphy, VMD; Frederick W. Oehme, DVM, PhD; Gary D. Osweiler, DVM, MS, PhD, DABVT; Mary M. Schell, DVM; David G. Schmitz, DVM, MS, DACVIM; Norman R. Schneider, DVM, MSc, DABVT