The Full Story
Even before the germ theory was presented by Louis Pasteur (of pasteurization fame) and even before antiseptic practices proposed by Joseph Lister (of Listerine fame) became commonplace, people knew that wounds needed treatment. Ancient texts from Mesopotamia describe washing wounds, making salves from plants and ash, and regular changing of wound dressings. Recipes from ancient Greece include wound treatment mixtures of honey, plants, wine, metals, and lanolin. They might not have known about bacteria, but they knew that untreated wounds could smell bad, heal poorly, and even lead to death.
The discovery and first use of chlorhexidine was in the United Kingdom in the 1950s. The chlorhexidine molecule has positive charges at each end. Bacteria and yeast cells tend to have negatively charged areas on their exteriors, and their interaction with chlorhexidine causes damage to the cell membranes of the microbes. In low chlorhexidine concentrations, this interaction slows the reproduction of the microbes. In high concentrations, the interaction is violent enough to tear apart the cell membrane, killing the microbe.
Although chlorhexidine is frequently used medically as a topical antiseptic, it is also known as a common contact allergen. A rash or irritation can develop on the skin of the area that came into contact with chlorhexidine. Symptoms can also include difficulty breathing or severe rash. In 2017, the FDA released a special alert requesting that manufacturers of over-the-counter chlorhexidine products add a warning about allergic reactions.
Chlorhexidine gluconate comes in many concentrations: 0.12% for oral use, 0.5% topical pad, 2% and 4% topical liquid and solution, 20% solution for disinfection, a mucous membrane chip with 2.5 mg used for gingivitis, as well as use in chewing gums, varnishes, and in toothpastes.
Low concentration oral forms of chlorhexidine do not typically pose a problem when unintentionally swallowed. However, even when using chlorhexidine mouthwashes as directed, a bitter aftertaste might be noticed and can last for several hours. Chlorhexidine is not well absorbed when swallowed, and some stomach irritation or nausea is typically all that will occur. Sometimes, people will vomit spontaneously, but do not ever induce vomiting. When an irritating substance like chlorhexidine is vomited, it can cause additional irritation to the esophagus.
Poison Control often gets calls from health care providers who unintentionally get a splash in the eye while applying the product topically or opening up chlorhexidine pads. When this occurs, the eye should be gently rinsed with tap water or eye rinse, for 15 minutes (see instructions for rinsing the eye). Depending on the concentration of chlorhexidine, it could simply be an irritant or it could cause damage to the cornea. If irritation or pain persists after rinsing and allowing the eye to rest, the eye should be evaluated by a health care professional.
Rarely, chlorhexidine has been unintentionally given by IV in a hospital. One man developed an acute respiratory distress syndrome (ARDS). This is a life-threatening syndrome, but the man survived after days of critical care.
If you think someone might be having adverse effects or has taken too much, immediately call Poison Control at 1-800-222-1222 or check the webPOISONCONTROL® online tool for guidance. Whether you call or log on, expert assistance is available 24 hours a day.
Pela Soto, PharmD, BSHS, BS
Certified Specialist in Poison Information
Friis-Møller A, Brynitz S, Jess P. Toxicity of chlorhexidine irrigation in chronic postpneumonectomy empyema. Scand J Thorac Cardiovasc Surg 1883;18:243-4.
Centers for Disease Control and Prevention. Guideline for hand hygiene in health-care settings. Recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force. MMWR Morbid Mortal Wkly Rep 2002;51(RR-16):1-45.
Chlorhexidine. POISINDEX System [Internet database]. Greenwood Village CO: Thomson Micromedex. Updated periodically. Accessed 4/19/2017.
Lim KS, Kam PC. Chlorhexidine--pharmacology and clinical applications. Anaesth Intensive Care 2008;36:502-12.
Manjo G. The healing hand: man and wound in the ancient world. Cambridge MA: Harvard University Press; 1975.
Nasser RE. The ocular danger of Hibiclens (chlorhexidine). Plast Reconstr Surg 1992;89:164-5.
Olson L, Björklund H, Henschen A, Palmer M, Hoffer B. Some toxic effects of lead, other metals and antibacterial agents on the nervous system--animal experiment models. Acta Neurol Scand Suppl 1984:100:77-87.
Toholka R, Nixon R. Allergic contact dermatitis to chlorhexidine. Australas J Dermatol 2013;54:303-6.
Wittczak T, Dudek W, Walusiak-Skorupa J, Swierczynska-Machura D, Palczynski C. Chlorhexidine-still an underestimated allergic hazard for health care professionals. Occup Med (Lond) 2013;63:301-5.