Chlorhexidine-Induced Anaphylaxis

Chlorhexidine induced anaphylaxis is an IgE-mediated reaction to chlorhexidine in skin antiseptics, urinary catheter gel, central venous catheters, mouthwash, dressings and wipes.

Epidemiology. Chlorhexidine causes about 0.5% to 10% of perioperative anaphylaxis cases (higher in some series), and is under recognised. Onset often occurs 20 to 40 minutes after exposure through mucosal absorption (catheter gel, central line), later than other triggers.

Risk factors. Previous chlorhexidine exposure (repeated), contact dermatitis to chlorhexidine, mucosal exposure, impregnated devices and atopy.

Pathophysiology.

Chlorhexidine acts as a hapten. Sensitisation leads to specific IgE, and mucosal absorption triggers mast cell degranulation and systemic anaphylaxis.

Hypotension, bronchospasm, rash, angioedema and collapse, often delayed by 15 to 45 minutes. Contact urticaria or dermatitis may precede. Identification may be missed because chlorhexidine is hidden in many products.

Red flags.

• Unexplained collapse after catheter insertion or line placement.
• Previous unexplained reaction during procedures.

Take serial tryptase (1 hour, 3 to 6 hours, baseline). Allergy referral at 4 to 6 weeks for skin prick testing (0.5 mg/mL) and intradermal testing (0.0002 mg/mL), specific IgE to chlorhexidine (cut off 0.35 kilounits/L) and basophil activation testing.

Differential diagnosis.

• Anaphylaxis to latex, antibiotics, neuromuscular blockers or dye.
• Sepsis from line insertion.
• Cardiac event.
• Pulmonary embolism.

Stop exposure by removing chlorhexidine products (wipe off skin, remove catheters impregnated with chlorhexidine, remove contaminated gel) and treat anaphylaxis.

• Adrenaline: 50 microgram IV titrated every 1 to 2 minutes, then infusion 0.05 to 0.1 microgram/kg/min; or 0.5 mg IM; in arrest 1 mg IV every 3 to 5 minutes; monitor ECG and blood pressure; avoid excess in ischaemia.
• Crystalloid: 20 mL/kg IV rapidly, repeat as needed; monitor for overload.
• Salbutamol: 5 mg nebulised for bronchospasm.
• Hydrocortisone: 200 mg IV once; maximum 400 mg daily.
• Chlorphenamine: 10 mg slow IV; maximum 20 mg daily.

Observe for at least 12 to 24 hours in a monitored setting.

Prevention and follow up. Record "chlorhexidine allergy" in the notes with an alert, and use an alternative antiseptic such as povidone iodine or an alcohol based non-chlorhexidine agent. Use non-chlorhexidine catheters, lubricant gels and dressings. Allergy referral.

Monitoring. ECG, blood pressure, saturation and tryptase.

Referral and escalation. Allergy service. Incident reporting.