Which statement about topical anesthetic is true?

• A. They numb deep tissues
• B. They have less than optimal effect on thick scars
• C. They are completely safe for all scar types
• D. They always provide complete numbness

Answer: (B)

Topical anesthetics work by blocking sodium channels in surface nerve endings, so their effect is limited to the skin layers they can reach. They don’t reliably numb deeper tissues. Thick scars create a dense barrier and can have altered nerve distribution, which makes diffusion harder and the numbing effect less effective. That’s why their effect on thick scars is typically suboptimal.

Numbing deep tissues would require infiltration or a nerve block, not a topical agent. They aren’t completely safe for all scar types—there are risks with any anesthetic, such as systemic toxicity or reactions in fragile or broken skin—and they don’t guarantee complete numbness in every case.