The sporadic type is thought to be caused by an allergy to a specific food or drug or by emotional stress. In the inherited type there is no specific cause of an attack. The condition is not thought to be serious unless it affects the mouth, throat, or larnyx, where it may obstruct breathing. In severe attacks treatment may include immediate injection of adrenaline followed by antihistamines and, possibly, steroids.
Prevention depends on identifying and eliminating the cause.