Pressure inhibition of the Koebner reaction by capillary occlusion.

A 38-year-old male with extensive psoriasis received a linear experimental abrasion. Immediate pressure was applied for 24 hours to the central portion of the traumatized site. During a psoriatic relapse 5 weeks later, Koebnerization occurred in the abraded areas but spared the site where pressure had been previously applied. The mechanism is not known but may be due to a local suppressive effect of pressure on inflammation.