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
Explore on this siteWhat are the causes of hives (urticaria)? Do viruses cause hives? Itchy skin causes for hives (urticaria)
- Australasian Society of Clinical Immunology and Allergy. ASCIA HP Position Paper Chronic Urticaria Guidelines 2020. Available from https://allergy.org.au/images/stories/pospapers/ASCIA_HP_Position_Paper_CSU_2020.pdf Accessed August 2021.
- Australasian Society of Clinical Immunology and Allergy. ASCIA PCC Hives Urticaria 2021. Available from https://allergy.org.au/patients/skin-allergy/urticaria-hives Accessed August 2021.
- Urb M and Sheppard DC. PLoS Pathog 2012; 8:e1002619.
- Asero R et al. F1000Research 2017; 6:1095.
- Bernstein JA et al. J Allergy Clin Immunol 2014; 133:1270-1277.