Darier’s sign refers to a change observed after stroking lesions on the skin of a person with systemic mastocytosis or urticaria pigmentosa.
With Darier’s sign the skin becomes swollen, itchy and red.
It is a result of compression of mast cells, which are hyperactive in these diseases.
These mast cells release inflammatory granules which contain histamine.
It is the histamine which is responsible for the response seen after rubbing the lesional skin.