Chlorhexidine (CHX) (commonly known by the salt forms chlorhexidine gluconate and chlorhexidine digluconate (CHG) or chlorhexidine acetate) is a disinfectant and antiseptic with the molecular formula C22H30Cl12N10, which is used for skin disinfection before surgery and to sterilize surgical instruments. It may be used both to disinfect the skin of the patient and the hands of the healthcare providers. It is also used for cleaning wounds, preventing dental plaque, treating yeast infections of the mouth, and to keep urinary catheters from blocking. It is used as a liquid or powder. Side effects may include skin irritation, teeth discoloration, and allergic reactions, although the risk appears to be the same as other topical antiseptics. It may cause eye problems if direct contact occurs. Use in pregnancy appears to be safe. Chlorhexidine may come mixed in alcohol, water, or surfactant solution. It is effective against a range of microorganisms, but does not inactivate spores. Chlorhexidine came into medical use in the 1950s. Chlorhexidine is available over the counter in the United States. It is on the World Health Organization's List of Essential Medicines. In 2020, it was the 273rd most commonly prescribed medication in the United States, with more than 1million prescriptions. Uses Chlorhexidine is used in disinfectants (disinfection of the skin and hands), cosmetics (additive to creams, toothpaste, deodorants, and antiperspirants), and pharmaceutical products (preservative in eye drops, active substance in wound dressings and antiseptic mouthwashes). A 2019 Cochrane review concluded that based on very low certainty evidence in those who are critically ill "it is not clear whether bathing with chlorhexidine reduces hospital‐acquired infections, mortality, or length of stay in the ICU, or whether the use of chlorhexidine results in more skin reactions." In endodontics, chlorhexidine has been used for root canal irrigation and as an intracanal dressing but has been replaced by the use of sodium hypochlorite bleach in much of the developed world. Antiseptic CHG is active against Gram-positive and Gram-negative organisms, facultative anaerobes, aerobes, and yeasts. It is particularly effective against Gram-positive bacteria (in concentrations ≥ 1 μg/L). Significantly higher concentrations (10 to more than 73 μg/mL) are required for Gram-negative bacteria and fungi. Chlorhexidine is ineffective against polioviruses and adenoviruses. The effectiveness against herpes viruses has not yet been established unequivocally. There is strong evidence that chlorhexidine is more effective than povidone-iodine for clean surgery. Evidence shows that it is the most effective antiseptic for upper