This page is intended for UK patients who have been prescribed remibrutinib for chronic spontaneous urticaria (CSU).1
The information on this website does not replace the Patient Information Leaflet which comes with your medication. Please always refer to your Patient Information Leaflet for more information. If you have any questions, ask your doctor or care team.
Your guide to chronic spontaneous urticaria
What is CSU?
Chronic spontaneous urticaria (er-tih-KAIR-ee-uh) is a skin condition that causes hives (also called ‘wheals’ or ‘urticaria’).2 Chronic spontaneous urticaria is commonly called ‘CSU’.
Hives look like raised, red or skin-coloured patches that can be itchy, hot, burning or uncomfortable:2
They may appear anywhere on the body and can change in size or move around during the day
They might join to form larger areas
People with CSU may get swelling on the face, neck, hands or feet.2 Your doctor may refer to this swelling as angioedema (AN-jee-oh-eh-DEE-muh).
Chronic?
In CSU, ‘chronic’ means that the hives appear on your skin most days for six weeks or longer.3
Spontaneous?
The hives and swelling in CSU appear without a clear cause.2–4 They are not brought on by specific things like food allergies, medicines or insect bites.
The exact reason CSU happens isn’t always known, but it’s thought to involve an overactive immune system causing the skin to release substances that lead to itching and swelling.2–4
Although CSU can be very uncomfortable, distressing and affect daily life, it is not contagious (you can’t catch it or pass it on to others) and is rarely life-threatening. However, if you experience swelling of your throat or tongue, or have difficulty breathing or swallowing, seek urgent medical attention.2
What causes CSU?2,3
CSU is caused by mast cells, which release substances such as histamine (HISS-tuh-mean) into the skin. This causes the redness, swelling and itching that are typical with CSU.
Mast cells are part of the immune system and are found throughout the body, especially in the skin, lungs and blood. They normally help to protect the body from infection, reduce inflammation and support wound healing.
In many people, the exact cause of CSU is not known. It is called ‘spontaneous’ because symptoms can appear without a clear trigger.
CSU is not caused by an allergic reaction to foods, environmental factors or other allergens.
Allergy tests or elimination diets are not usually helpful in diagnosing or managing CSU.
Around half of CSU cases are linked to autoimmune disease. This means the immune system mistakenly attacks healthy cells in the body.
Your healthcare team may recommend blood tests to look for markers of autoimmune disease.
How might CSU affect me?
CSU can affect people in different ways. Because the itching and swelling can come and go suddenly, they may affect different aspects of life.2,3
Sleep problems: itching or discomfort can make it hard to rest properly2,3
Tiredness (fatigue): poor sleep and ongoing symptoms can leave you feeling drained2,3
Frustration or feeling self-conscious: visible hives or swelling might make you feel embarrassed2,3
Difficulty concentrating: itching or discomfort can make it hard to focus at work, school or during daily life2,3
Living with an unpredictable condition can also be emotionally challenging2,3
Some people feel anxious or low because they don’t know when the next flare-up will happen2,3
How long does CSU last?
For most people who are untreated or treated with medicines like antihistamines, CSU gradually improves over time.4
Around half of people are free from symptoms within 6 months to 5 years, though this may take longer if you also experience swelling (angioedema).5
For some people (around 1 in 5), CSU can last for 10 years or more.5
Rhapsido®▼ (remibrutinib)
Remibrutinib is a medicine that can help to manage CSU in adults whose symptoms are not controlled with antihistamine treatment.6
Learn more about remibrutinib
CSU, chronic spontaneous urticaria.
References
Rhapsido® (remibrutinib) Patient Information Leaflet.
AllergyUK. Chronic Spontaneous Urticaria (CSU). Available at: https://www.allergyuk.org/resources/csu/ [Accessed August 2026].
Zuberbier T, et al. Allergy 2026;81(8):2582–2632.
Maurer M, et al. Allergy 2011;66(3):317–330.
Sabroe RA, et al. Br J Dermatol 2022;186(3):398–413.
Rhapsido® (remibrutinib) Summary of Product Characteristics.
UK | September 2026 | FA-11723601
Reporting side-effects
If you get side-effects with any medication you are taking, talk to your doctor, pharmacist or nurse. This includes any possible side-effects not listed in the information leaflet that comes in the pack. ▼ The medicine referred to in this material is subject to additional monitoring. This will allow quick identification of new safety information. You can help by reporting any side-effects you may get. Please see www.mhra.gov.uk/yellowcard. for instructions on how to report side-effects.
