Pressure urticaria: An uncommon type of hives (urticaria) that occurs after the skin has been under pressure, often the feet after standing or the buttocks after sitting for a long time or areas where clothing is tight. The hives may begin hours after the pressure on the skin has ceased. The hives last 8 to 72 hours and may be painful, itchy, or burning. They may be accompanied by low fever, chills, fatigue, joint and muscle aches, and/or headaches. Triggers include pressure from using tools (such as a screwdriver or a hammer), clapping the hands, carrying a bag or suitcase, sexual intercourse, and the use of tampons. Antihistamines may not help. Nonsteroidal anti-inflammatory drugs (NSAIDs) or oral steroids may be used. The disease tends to be chronic and last for years. The cause is unknown.