Chronic hives (urticaria) causes

Failure to identify the cause of chronic hives can be very frustrating. What is clear is that allergy is not one of the chronic urticaria causes.¹

How do the hives form?

Hives are the result of mast cells being activated by your immune system to release histamines and other chemicals into the affected area, which in turn results in red, itchy, swollen skin.² Mast cells occur in parts of the body that are exposed to our surroundings – e.g. in skin and mucous membranes. They recognise threats such as foreign bacteria or parasites which activates them to release histamines and other chemicals.³ This is a normal surveillance system, but in urticaria the mast cells are activated without any external threat.

 

What happens in the skin of people with chronic urticaria (CU)

Chronic urticaria triggers

Some forms of chronic hives have known physical triggers, but most do not.

• In chronic inducible urticaria the triggers are known and include temperature, solar light and pressure among other things.
• In chronic spontaneous urticaria there is no known trigger, which makes it impossible to predict when an outbreak will occur.

Chronic spontaneous urticaria causes

There are several causes of chronic spontaneous urticaria:

• Autoantibodies – approximately 50% of people with chronic spontaneous urticaria have an autoantibody, which is an antibody that attaches to mast cells and other immune cells to activate them even when there is no threat⁴
• Autoallergies – this is where a specific allergy antibody recognises one of your proteins (e.g. a thyroid protein) which activates the mast cells⁴
• Autoimmune disorder – there is a strong association between chronic spontaneous urticaria and other autoimmune disorders.¹
• Underlying infections – certain bacterial infections have been linked to people with chronic spontaneous urticaria.⁵