Common causes of urticaria include infections, contact with plants or animals, and allergic reactions to foods, medications, or insect bites. They typically appear 1-2 hours after contact with the allergen and disappear within 6-8 hours, although they may last up to 24 hours. Stress is not a common cause of urticaria; while it may rarely trigger it, it is more likely to worsen existing symptoms. Other potential triggers include cold, heat, sunlight, vibration, rubbing the skin, wearing tight clothing, exercise, sweating, stress, alcohol or caffeine consumption, and eating spicy foods.