Hives on dark skin. Hives are a skin reaction that causes red or white itchy welts. The welts vary in size and appear and fade repeatedly as the reaction runs its course. Chronic hives are a condition in which the welts last more than six weeks or recur over months or years.Chronic hives usually aren't life-threatening. But the condition can be very uncomfortable and interfere with sleep and daily activities. Often, the cause of chronic hives is not clear.In some cases, chronic hives are a sign of an underlying health problem, such as thyroid disease or lupus. You can try various treatments to relieve your symptoms. For many people, antihistamine and anti-itch medications provide relief from chronic hives.hronic hives are a condition in which the welts last more than six weeks or recur over months or years. Chronic hives usually aren't life-threatening. But the condition can be very uncomfortable and interfere with sleep and daily activities. Often, the cause of chronic hives is not clear.
longitudinal magnetization. 1  of a material or medium in a manner in which the magnetic flux is essentially parallel to the long axis of the influencing field. 2  In magnetic recording, 3  of a material or medium essentially in the same direction as the material or medium is traveling.
Longitudinal wave. From Wikipedia, the free encyclopedia. Longitudinal waves, also known as l-waves, are waves in which the displacement of the medium is in the same direction as, or the opposite direction to, the direction of travel of the wave.rom Wikipedia, the free encyclopedia. Longitudinal waves, also known as l-waves, are waves in which the displacement of the medium is in the same direction as, or the opposite direction to, the direction of travel of the wave.