This is probably one of the biggest areas of frustration and confusion for people suffering hives, because in many cases the cause of hives is unknown. It may be useful to think about it in two ways: what causes the disease in the first place and what triggers an outbreak.
All forms of hives involve the immune system and, specifically, mast cells. Mast cells are an important part of the immune system and occur in areas of the body that encounter your surroundings – e.g. in skin and mucous membranes. They recognise threats such as foreign bacteria or parasites and become activated to release histamines and other chemicals. These chemicals send messages to other parts of the immune system so that a response can be mounted to fight any foreign invaders.1
Urticaria is a condition that occurs when the mast cells are activated without any external threat. The histamines and other chemicals released by the mast cells result in red, itchy, swollen skin.2
Chronic spontaneous urticaria
The underlying causes for the over-active immune system in chronic spontaneous urticaria can include:1-4
- Antibodies that automatically recognise and activate mast cells (called autoantibodies)
- Allergy antibodies recognising a protein such as a thyroid protein, resulting in mast cell activation; this is not a real allergy because the reaction is caused by something within your body rather than something external such as food, pollen or a plant5
- Other autoimmune diseases.
Even though the underlying cause may be known, the exact trigger for the hives outbreak is most often not known, which is the case for chronic spontaneous urticaria. This makes the disease very difficult to manage as the hives can appear at any time.6
Chronic inducible urticaria
In the case of chronic inducible urticaria the physical trigger is known. Triggers include temperature, solar light and pressure among other things.
The causes of acute hives are usually viruses, allergies or insect stings.7
What happens in the skin of people with chronic urticaria (CU)
Explore on this siteStress hives – is it a real condition? Lifestyle tips for people with stress-induced hives Do viruses cause hives? Chronic urticaria causes – what are they? Itchy skin causes for hives What are common allergy hives caused by?
- Urb M and Sheppard DC. PLoS Pathog 2012; 8:e1002619.
- Australasian Society of Clinical Immunology and Allergy. Hives (urticaria). 2017. (accessed 9 Oct 2018).
- Zuberbier T et al. Allergy 2-18; 73:1393-1414
- Bernstein JA et al. J Allergy Clin Immunol 2014; 133:1270-1277.
- Asero R et al. F1000Research 2017; 6:1095.
- Australasian Society of Clinical Immunology and Allergy. ASCIA Chronic Spontaneous Urticaria (CSU) Guidelines. 2015. (accessed 9 October 2018).
- Fine LM and Bernstein JA. Allergy Asthma Immunol Res 2016; 8:396-403.