Which sign indicates further dermal separation when a blister is pushed?

The Nikolsky sign is a clinical examination finding where gentle pressure on the skin causes the epidermis to separate from the underlying dermis, leading to more areas of blistering or skin erosion. This sign is particularly significant in conditions such as pemphigus vulgaris, where the integrity of the skin is compromised due to autoimmune processes.

When conducting the Nikolsky test, the clinician applies lateral pressure to the skin surface adjacent to a blister. If the skin layers separate readily, this indicates a weakened cohesion between the epidermal layer and the dermis, and further blister formation can occur. This is a key characteristic seen in certain blistering disorders, making it an important diagnostic tool in dermatology.

Other terms like the Auspitz sign, which involves the appearance of pinpoint bleeding when psoriatic scales are removed, the Koebner phenomenon indicating skin lesions manifesting at sites of trauma in certain skin conditions, and dermographism which refers to the skin's reaction to physical stimuli (like scratching) do not relate to the dermal separation response observed with the Nikolsky sign. Therefore, the Nikolsky sign is the correct choice when assessing for further dermal separation in blisters.