Case hardening is a weathering phenomenon of rock surface induration. Manifestation of infection tends to involve erythema, induration, itching, and scaling. In chronic vestibulitis, induration of vestibular skin and crusting is seen. Typical signs include periorbital erythema, induration, tenderness and warmth. The surface induration by means of this process is named case hardening. TST (tuberculin skin test) positive is measured by size of induration. Arthus reactions are characterized by severe pain, swelling, induration, edema, hemorrhage, and occasionally by necrosis. The size of the induration considered to be a positive result depends on risk factors. Induration, contact bleeding and rolled margins are features of a malignant ulcer. Redness and scleroderma-like induration occurs on the skin. If there is no induration, the result should be recorded as "0 mm". Residual induration, however, is rare and usually these areas completely resolve. In addition, there may be brownish-red pigmentation and induration too.