Chronic spontaneous urticaria (CSU) is a disease that causes recurring episodes of red, bumpy, itchy skin called urticaria, or hives. Most experts now believe that autoimmunity plays a role in most cases of chronic spontaneous urticaria (CSU), but the science is still evolving.
An autoimmune disease is a chronic condition in which part of your immune system mistakenly attacks part of your own body. This leads to inflammation and damage.
Chronic spontaneous urticaria symptoms occur when a type of immune cell called a mast cell gets activated. The reason for this activation depends on the type of CSU you have.
There are two main types of CSU. They have the same symptoms but slightly different causes. Many scientists now think both these subtypes are autoimmune.
Type 1 CSU
Type 1 CSU—sometimes called type 1 autoimmune CSU—involves part of the immune system called IgE antibodies. Some of these antibodies get abnormally programmed to attack some of your own proteins. If the IgE runs into any of these proteins, it triggers mast cells to activate.
People with type 1 CSU tend to have less severe symptoms compared to those with the other type of CSU. They are also less likely to have other autoimmune conditions.
Type 2b CSU
This type is sometimes called type 2b autoimmune CSU. With this type, a different kind of antibody, called IgM, gets abnormally programmed. For example, the IgM antibodies may start attacking parts of IgE antibodies. This also triggers the mast cells to activate, setting off symptoms.
Other Unknown Types
Roughly a third of people with CSU don’t have either known subtype. It’s unclear whether they have another undiscovered kind of autoimmune CSU or another problem that is causing their symptoms.
CSU and an allergic reaction share similar features, including their causes. In both conditions, the immune system is involved. Specifically, symptoms occur when mast cells are activated. The symptoms of a CSU episode and an allergic reaction are also similar.
A main difference between the two conditions is that, in CSU, the symptoms happen spontaneously, without a known trigger. An allergic response is triggered when the immune system overreacts to harmless environmental triggers, such as pollen.
CSU doesn’t directly cause other autoimmune conditions. However, people with CSU do seem to have an increased risk of having other autoimmune diseases, such as:
- Autoimmune hypothyroidism
- Autoimmune hyperthyroidism
- Celiac disease
- Lupus
- Rheumatoid arthritis
If you think you might have CSU, share your concerns with a healthcare provider. Take pictures of your rash to show your provider, and tell them if the area was bumpy or flat. For serious symptoms, like difficulty breathing or rash with a fever, get immediate medical attention.
