Pathergy phenomenon is defined as a state of altered tissue reactivity that occurs in response to minor trauma Although the exact mechanisms underlying pathergy phenomenon are unknown, skin injury caused by needle prick apparently triggers a cutaneous inflammatory response . Types of pathergy tests: Oral pathergy test Site: lower lip. Skin pathergy test Site: A hairless area on the flexor aspect of the forearm sterile needle (20 gauge) prick or an intradermal injection of normal saline, monosodium urate (MSU) crystals or streptococcal antigens to perform the test. The procedure is performed on a hairless pa of the volar forearm. Generally, the needle is inseed veically or diagonally at an angle of 45deg to a depth of 3-5 mm. The needle should reach the dermis for a proper response. Clinical evaluation: Readings are taken after 48 hrs of the needle prick. A 1-2mm papule that is usually felt by palpation and which is surrounded by an erythematous halo is formed on the skin. The papule may remain as a papule or transform into a 1-5mm pustule. The pustule becomes prominent in 24 h, becomes maximum in size in 48 h, and disappears in 45 days. Erythema without induration is interpreted as a negative result. Conditions with positive pathergy phenomenon: Behcet's disease Pyoderma gangrenosum (PG): The pathergy test positivity at a rate of 25% has been repoed in the literature in PG patients. Aggressive surgical debridement or skin grafting is discouraged in these patients because of the risk of a pathergic response. Interferon alpha-treated chronic myeloid leukemia patients Sweets syndrome Eosinophilic pustular folliculitis Inflammatory bowel disease Healthy individuals Rarely in spondyloahropathies Ijdvl Sequeira FF, Daryani D. The oral and skin pathergy test. Indian J Dermatol Venereol Leprol 2011 ;77:526-30. Available from: