A patient presents with painful, highly corrosive burns that resemble acid exposure and wheals on the skin. Which vesicant (blister agent) is suspected?

• A. Sulfur mustard
• B. VX
• C. Phosgene oxime
• D. Lewisite

Answer: (C)

Phosgene oxime stands out because it is the fastest-acting vesicant, causing immediate, highly painful and corrosive tissue injury that can resemble an acid burn with wheal-like skin changes. This rapid, severe reaction on contact is the hallmark that matches the description given. Sulfur mustard tends to produce blistering hours after exposure, not right away, and Lewisite also causes rapid pain but with different distinguishing features and arsenic-related effects. VX is a nerve agent, not a blister agent, so it wouldn’t present as a vesicant burn. Thus the immediate, acid-like burns with wheals point to phosgene oxime.