Which surgical prep solution is not effective against organic matter?

• A. Chlorhexidine
• B. Alcohol
• C. Iodine
• D. Water

Answer: (C)

When selecting a surgical prep, the key idea is how well the agent works in the presence of organic material like blood or tissue fluids. Organic matter can bind or neutralize antiseptics, reducing their ability to kill microbes.

Iodine works by releasing iodine to penetrate and disrupt microbial cells, but organic matter binds iodine and lowers the amount of free, active iodine available. That binding reduces its antimicrobial action in a soiled field, making it less effective against organic debris. That’s why, in practice, iodine-based preparations can be less reliable when significant organic matter is present.

Chlorhexidine and alcohol tend to retain strong antimicrobial activity even with moderate organic load, and water has no antiseptic effect at all. The best approach is to clean away organic debris first, then apply the antiseptic to maximize effectiveness.