Chlorhexidine

Mechanism of action

Chlorhexidine is a cationic biguanide, used as the water-soluble digluconate salt. It adsorbs strongly to bacterial membranes, which then leak small molecules, and at higher levels it precipitates cytoplasmic proteins. It kills vegetative bacteria and mycobacteria, is most effective against gram-positive cocci and less against gram-negative and gram-positive rods, and has variable activity against fungi and viruses; it inhibits spore germination but does not kill spores. It acts more slowly than alcohol but binds to the skin and keeps acting (residual activity), and it is not inactivated by blood or organic matter. Combined with alcohol it acts fast and persists, which is why it is preferred for surgical skin preparation.

1. Cationic chlorhexidine adsorbs strongly to the bacterial membrane
2. Small molecules leak out; cytoplasmic proteins precipitate
3. Bacteria die, gram-positive cocci most readily
4. It stays bound to skin and keeps acting after drying

Indications

• Surgical site skin preparation (alcohol-based solution) Surgical site infection →
• Surgical hand scrub and hand antisepsis for health workers
• Cleansing of skin and minor wounds
• Body wash, with nasal mupirocin, for known S. aureus carriers before surgery Surgical site infection →
• Umbilical cord care in newborns where omphalitis is common (WHO list)

Adverse effects

Common

• Skin irritation or redness
• Contact sensitisation (uncommon)
• Staining of fabrics washed with chlorine-releasing laundry products

Contraindications

• Hypersensitivity to chlorhexidine
• Use in the middle ear or on the meninges
• Use in the genital area and in deep wounds (skin products)

Key interactions

Soaps, moisturisers and surfactants with anionic or non-ionic agents

Can neutralise chlorhexidine's activity.

Chlorine-releasing laundry products

Stain fabrics that carry chlorhexidine; the fabric is rinsed well and washed with non-chlorine detergent.

What is monitored

• Skin at the application site, especially in premature and young infants
• Signs of allergy during and after procedures (hives, wheezing, facial swelling, dizziness)

Administration and safety

• Alcohol-based solutions are left to dry completely before draping, diathermy or laser: they are flammable.
• Kept out of the eyes, ears and mouth; eyes are rinsed with cold water if splashed.
• Not used in the middle ear, on the meninges or in deep wounds.
• Used with care in premature infants and young infants, where it can irritate or burn the skin.

Nursing care

• Ask about previous reactions to chlorhexidine, including from catheters, gels or mouthwash.
• Check that the prep has dried before the procedure starts.
• Watch for hives, wheezing, facial swelling or dizziness after exposure and report at once.
• Avoid repeated washing of large body areas unless prescribed.

Pharmacokinetics

Absorption

Poorly absorbed from the gut, so oral toxicity is low; on skin it binds and stays active.

Onset and duration

Slower than alcohol, but with persistent residual activity.

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Connections

← Back to the class: Antiseptics, disinfectants and sterilants

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Chlorhexidine Topical: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Global guidelines for the prevention of surgical site infection (World Health Organization, 2018); eEML - Electronic Essential Medicines List (World Health Organization, 2025).

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