It's important to understand the difference between causes of hives and the factors that can influence them; causes are the internal processes in the body that produce symptoms, while external factors can prompt these processes.
The internal processes in the body that cause hives are carried out by the immune system. Your immune system is there to protect your body from infections, but in some cases, it can become overactive and cause unwanted symptoms. In allergic or physical forms of hives, certain external factors, such as pollen, heat or pressure, can set off this immune response and lead to visible skin reactions.
In chronic spontaneous urticaria (CSU), however, there is no identifiable external trigger. The immune system is activated without any clear external factor, which can result in itching, redness, or swelling.1
A systemic disease is one that affects the entire body or multiple organs, rather than just one localized area. The disease processes occur throughout the entire body and can cause a wide variety of symptoms.
Chronic spontaneous urticaria (CSU) is often thought of as a skin condition, but it actually involves specialized immune cells all throughout the body, not just the skin. That's why it's considered a systemic disease.
These specialized immune cells, called mast cells, play a key role in CSU.2 These cells are part of your body's normal defense system and are found in many tissues throughout the body, including the skin. When activated, mast cells release a substance called histamine into these nearby tissues - this causes the visible symptoms of urticaria, like redness, itching, or swelling.3
In CSU, mast cells get activated when the immune system mistakenly reacts to harmless substances, or even to the body's own tissues. This overreaction triggers mast cells to release histamine when they shouldn't. In about half of CSU cases, this process is autoimmune, meaning the body reacts against itself.
Since mast cells are so concentrated in the skin, urticaria symptoms like itching, redness, and swelling are most noticeable there.3 However, mast cells are also found in other areas of the body, such as the intestinal lining, which explains why symptoms can sometimes affect more than just the skin.
In chronic spontaneous urticaria (CSU), however, there is no identifiable external trigger. The immune system is activated without any clear external factor, which can result in itching, redness, or swelling.1 Information about the different types of hives and symptom patterns may support discussions during medical consultations.
Chronic hives is not usually caused by an allergy. Check how your hives are impacting your life and take the results to your Specialist.
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Australasian Society of Clinical Immunology and Allergy (ASCIA) Australasian College of DermatologistsReferences
- Powell RJ, et al. BSACI guideline for the management of chronic urticaria and angioedema. Clin Exp Allergy 2015;45(3):547-65.
- Friedman A, et al. Dermatol Ther (Heidelb).Adis. 2024;14(6):1371-87.
- Metcalfe DD, et al. Physiol Rev 1997;77(4).