What sign indicates rubs that cause an urticarial flare?

The correct answer involves understanding what Darier's sign refers to in clinical practice. Darier's sign is characterized by the appearance of urticarial wheals or flares when a specific area of skin is rubbed or scratched, which indicates the presence of a mast cell disorder often associated with conditions such as mastocytosis. This sign is significant in the context of skin disorders and helps in diagnosing conditions that may present with similar symptoms.

In contrast, the other signs have specific meanings in different medical contexts. Chadwick's sign is indicative of early pregnancy, reflecting increased blood flow and engorgement of the vaginal area. Finkelstein's sign is used to diagnose de Quervain's tenosynovitis, where pain is elicited by specific wrist movements. Homan's sign is traditionally associated with the detection of deep vein thrombosis by eliciting pain in the calf upon dorsiflexion of the foot. Each of these signs serves a distinct purpose in medical evaluation and is not concerned with urticarial flares caused by skin rubbing, which is why Darier's sign is the relevant answer.