Nikolsky's sign is defined as blister spreading with pressure.

• A. With pressure, blister spreads
• B. Blister forms spontaneously
• C. Blisters are non-tender
• D. It indicates bacterial infection

Answer: (A)

Nikolsky's sign shows loss of cohesion between epidermal cells. When light rubbing or lateral pressure is applied to skin, the outer layer can slide off and a blister can extend into surrounding areas—so the blister spreads with pressure. This happens because diseases like pemphigus vulgaris disrupt desmosomes that hold keratinocytes together, making the skin unusually fragile. The test is considered positive when this spreading occurs.

It's not about spontaneous blister formation, tenderness, or indicating a bacterial infection by itself. Spontaneous blisters or tenderness aren’t the defining feature, and while some bacterial-related conditions can produce superficial skin damage, Nikolsky's sign specifically reflects epidermal adhesion loss rather than infection.