What is the effective concentration of Alcohol-Based Hand Rub (ABHR)?

Effective Concentration of Alcohol-Based Hand Rub (ABHR)

The most effective concentration for Alcohol-Based Hand Rub (ABHR) is 60-95% alcohol, with 70-85% being optimal for maximum antimicrobial efficacy while maintaining appropriate skin tolerance. 1

Optimal Alcohol Concentration

Alcohol solutions demonstrate a concentration-dependent efficacy profile:

• 60-95% alcohol concentration is most effective for hand hygiene
• Concentrations below 60% show significantly reduced antimicrobial activity
• Concentrations above 95% are actually less potent because proteins are not denatured easily in the absence of water 1

Specific Alcohol Types and Their Effective Ranges:

• Ethanol: 60-85%
• Isopropanol: 60-80%
• n-Propanol: 60-80% 2

Volume and Application Considerations

The volume of ABHR applied is critical for effectiveness:

• Small volumes (0.2-0.5 mL) are no more effective than washing with plain soap and water
• 1 mL is substantially less effective than 3 mL 1
• Sufficient volume should be used so hands do not feel dry after 10-15 seconds of rubbing 1

Application Time

Duration of application significantly impacts effectiveness:

• 30-second application may be insufficient for some formulations
• 60-second application time ensures most formulations meet European efficacy standards 3
• If hands feel dry after rubbing for 10-15 seconds, insufficient volume was likely applied 1

Formulation Matters

Product formulation can greatly influence overall antimicrobial efficacy:

• Formulation is more important than alcohol concentration alone 4
• Addition of emollients can improve skin tolerance without reducing efficacy 2
• WHO-recommended formulations (80% ethanol or 75% isopropanol) meet efficacy requirements when applied for 60 seconds 3

Common Pitfalls and Caveats

Ineffective Against Certain Pathogens

• ABHRs are not effective against bacterial spores, particularly Clostridium difficile 5
• For C. difficile and other spore-forming organisms, handwashing with soap and water is recommended

Skin Reactions

• Irritant contact dermatitis is the most common reaction to alcohol-based products
• Risk factors include frequent use, pre-existing skin damage, low humidity environments
• Well-formulated alcohol-based hand rubs containing emollients have lower irritation potential than antimicrobial soaps 6, 2

Fire Hazard

• Alcohols are highly flammable, creating a significant fire hazard
• Caution is needed when using near heat sources or open flames 6

Practical Application Algorithm

1. Select appropriate ABHR concentration:

   • Choose products with 70-85% alcohol concentration for optimal balance of efficacy and skin tolerance
   • Ethanol-based products at 80% concentration are recommended for general use

2. Apply correct volume:

   • Use sufficient volume (approximately 3 mL) to keep hands wet during rubbing
   • Ensure complete coverage of all hand surfaces

3. Maintain proper contact time:

   • Rub hands until completely dry (typically 20-30 seconds)
   • For maximum efficacy, maintain contact for 60 seconds

4. Consider special circumstances:

   • For spore-forming organisms (e.g., C. difficile), use soap and water instead
   • For users with skin sensitivity, select formulations with added emollients

By following these guidelines, healthcare providers can maximize the effectiveness of ABHR while minimizing adverse effects and ensuring patient safety.