Chlorhexidine: Broad-Spectrum Antiseptic for Wounds, Mouth and Catheters
Chlorhexidine is a bisbiguanide antiseptic compound that has been in clinical use since the 1950s. It is one of the most thoroughly studied and widely used topical antiseptics in the world, with applications in oral hygiene, wound care, surgical skin preparation, catheter care, and general hand hygiene. Its activity spans gram-positive bacteria, gram-negative bacteria, fungi, and some enveloped viruses.
The persistence of chlorhexidine on treated surfaces (substantivity) is a key clinical advantage: it remains bound to skin and mucous membrane proteins for several hours after application, providing prolonged antimicrobial activity beyond the immediate contact period. This property sets it apart from simple detergents or alcohol-based antiseptics.
Mechanism of Action
Chlorhexidine is a cationic compound that binds to negatively charged bacterial cell membranes due to electrostatic attraction. At low concentrations, chlorhexidine causes bacteriostasis by disrupting osmotic balance; at higher concentrations, it causes direct membrane rupture with release of cytoplasmic contents, leading to rapid cell death. The cationic molecule binds strongly to skin proteins, mucin, and salivary proteins, enabling its prolonged residual effect. Chlorhexidine does not penetrate intact skin to a clinically relevant extent, limiting systemic toxicity from topical use. Unlike iodine-based antiseptics, chlorhexidine activity is not substantially reduced by organic matter such as blood or pus, maintaining effectiveness in clinical wound environments.
Indications
Oral chlorhexidine mouthwash (0.12 to 0.2 percent) is a well-established adjunct treatment for gingivitis, periodontitis, and oral hygiene maintenance in immunocompromised patients. Chlorhexidine solutions (0.5 to 2 percent in water or alcohol) are used for preoperative skin disinfection, reducing surgical site infection risk. Chlorhexidine impregnated dressings and skin patches reduce central venous catheter-related bloodstream infections. Wound irrigation with dilute chlorhexidine solutions is used for contaminated wounds. Chlorhexidine shampoos are used for seborrhoeic dermatitis and scalp infections.
Dosage and Administration
For gingivitis: 0.12 to 0.2 percent mouthwash used twice daily for 30 seconds, typically for two weeks of intensive treatment followed by maintenance as needed. For wound care: 0.05 to 0.5 percent aqueous solution applied to wounds; higher concentrations may impair wound healing. For surgical skin preparation: 2 percent chlorhexidine in 70 percent isopropyl alcohol (the most effective combination) applied with friction and allowed to dry before incision. For vascular catheter care: 2 percent chlorhexidine swabs for exit site care. Concentration selection must balance antiseptic efficacy against tissue irritancy.
Side Effects
Oral staining of teeth and tongue is the most common side effect with regular mouthwash use; the brownish discolouration is reversible with professional cleaning and correlates with tannin-rich food and beverage consumption. Altered taste perception and burning sensation in the mouth are common during intensive treatment. Mucosal desquamation has been reported with concentrated preparations. Anaphylaxis and severe allergic reactions are the most serious adverse effects and have been reported with chlorhexidine in all forms including topical and injectable preparations; healthcare workers have a higher prevalence of sensitisation due to occupational exposure. Concentrated solutions (greater than 0.5 percent) can irritate and damage wound tissues and should not be used in enclosed body cavities.
Interactions
Chlorhexidine is inactivated by anionic surfactants present in some toothpastes (sodium lauryl sulphate); patients should wait at least 30 minutes after brushing before using chlorhexidine mouthwash. Chlorhexidine is incompatible with iodine-based products and may precipitate or be inactivated when mixed. Hard water minerals can reduce chlorhexidine efficacy. Compatibility with other topical agents should be verified before combined use in wound care.
Special Notes
Chlorhexidine should not be used in the ear canal as it is ototoxic and can cause sensorineural hearing loss if it enters the middle ear. Injectable or irrigation solutions containing chlorhexidine must be clearly distinguished from topical preparations to prevent inadvertent intravascular or intracavitary administration. Medical grade chlorhexidine products must be used for clinical applications; household cleaning products are not suitable substitutes. Chlorhexidine allergy is a reportable hypersensitivity that should be clearly documented in patient records and communicated at every healthcare encounter.
Related Topics
Frequently Asked Questions
Why does chlorhexidine stain teeth?
Chlorhexidine binds to salivary proteins and pellicle on the tooth surface. These complexes can absorb chromogens from tea, coffee, red wine, and other coloured foods and beverages, forming visible brown deposits. The staining is extrinsic (surface-level) and can be removed by professional cleaning. Using alcohol-free formulations and minimising tannin-rich foods during treatment reduces staining.
Can chlorhexidine cause allergic reactions?
Yes, chlorhexidine is an increasingly recognised cause of perioperative anaphylaxis. Healthcare workers have higher rates of sensitisation due to repeated occupational exposure. Reactions range from contact dermatitis to life-threatening anaphylaxis. All patients should be asked about chlorhexidine sensitivity before procedures, and medical records must clearly document known allergy.
Is chlorhexidine mouthwash safe for long-term use?
Long-term continuous daily use is generally not recommended due to tooth staining, altered taste, and mucosal effects. Standard practice involves short intensive courses of two to four weeks for acute gingivitis, followed by intermittent maintenance use. In high-risk patients (post-surgical, immunocompromised), longer supervised use may be appropriate under dental guidance.
Sources
- EMA: Chlorhexidine Summary of Product Characteristics 2023
- Lim KS et al: Chlorhexidine Anaphylaxis. Br J Anaesth 2022
- EFP Guidelines on Gingivitis Management 2023