Understanding Chronic Spontaneous Urticaria (CSU)
If you’ve ever had hives, you know how uncomfortable those red, itchy welts can be. Hives, also known as Urticaria, usually go away on their own. But sometimes they last for weeks or months, and doctors can’t pinpoint the cause. When this happens, it’s referred to as Chronic Spontaneous Urticaria (CSU).
„It can be very frustrating for patients because unlike other types of hives, we can’t simply tell them to avoid a specific allergen or trigger like cold or sunlight,“ says Dr. Jeffrey Cohen, a dermatologist at Yale School of Medicine. „CSU can persist for months or even years, although it does eventually improve in most cases.“
Hives are common, affecting an estimated 20% of Americans at some point. CSU, however, is much rarer, with less than half a percent of people in the United States ever experiencing it. It most commonly affects adults between 20 and 40 years old, with women being twice as likely to develop CSU compared to men.
What Does CSU Look Like?
CSU appears similar to regular hives: clusters of red or skin-colored welts that can occur anywhere on the body, explains Dr. Michael Cameron, Assistant Professor of Dermatology at Mount Sinai Health System in New York. They typically itch and can vary in size and shape. While they usually disappear within 24 hours, in contrast to acute hives, they often recur, with complete episodes lasting longer than six weeks. The trigger for this recurrence is unknown.
„Through careful history-taking, doctors sometimes find that a patient’s hives may be linked to exposure to sunlight, water, or pressure from a heavy bag or seatbelt over several hours,“ says Cameron. „But for patients with CSU, the cause of their hives remains a mystery.“ Many people with CSU also experience a condition called angioedema, which involves swelling and puffiness on areas like the lips, cheeks, eyelids, hands, or feet.
What Causes CSU?
The root cause of CSU is not clearly understood. „Chronic spontaneous Urticaria was previously known as chronic idiopathic Urticaria, meaning that we don’t exactly know what causes it,“ says Cohen.
If your hives persist for longer than six weeks, even if they come and go, your doctor will most likely refer you to a specialist such as an allergist or dermatologist for more specific tests, says Dr. Tiffany Owens, an allergist at Wexner Medical Center at Ohio State University. These tests may include a physical examination in the clinic and blood tests for:
- Thyroid hormone levels: Nearly 30% of cases of CSU are associated with Hashimoto’s disease, an autoimmune condition that impairs thyroid hormone production. „Treating Hashimoto’s usually leads to a complete disappearance or improvement of hives,“ explains Owens.
- Erythrocyte sedimentation rate (ESR): This indicates the level of inflammation in your body. A high ESR may suggest an autoimmune condition causing hives. „One theory is that CSU is an autoimmune condition where your immune system attacks your own allergy cells,“ Owens elaborates.
- Hepatitis: Occasionally, Hepatitis B or C can trigger CSU, according to Owens.
Your doctor might also consider performing a skin biopsy by taking a small skin sample and examining it under a microscope. This is often recommended if your CSU is accompanied by other symptoms like fever, pain, hives lasting for days, or hives causing bruising.
If your doctor conducts all these tests and doesn’t find a clear cause, they will likely focus on treating the hives.
Is CSU Treatment Different?
If your doctor suspects you have CSU, they will often prescribe the same medications recommended for acute hives but in different dosages. „While for acute Urticaria, your doctor may suggest taking over-the-counter antihistamines like Cetirizine (Zyrtec) or Loratadine (Claritin) as needed to relieve itching,“ says Cohen.
However, for CSU, the focus is on taking high doses daily to prevent the hives from occurring at all. Your doctor may instruct you to take three to four times the recommended dosage daily while carefully monitoring you for side effects such as dry mouth and nausea.
If these measures don’t help, your doctor may explore other medications such as:
- H2 blockers: These prevent the substances causing itching and hives from binding to receptors on certain cell types. They are found in heartburn medications like Cimetidine (Tagamet), Famotidine (Pepcid), and Ranitidine (Zantac).
- Corticosteroids: Drugs like Prednisone can alleviate swelling and itching, but are not recommended for long-term use due to potential severe side effects.
- Leukotriene modifiers: Medications like Montelukast, commonly used for asthma and allergies, may also help with CSU.
- Doxepin (Silenor): An antidepressant that also prevents histamines from binding to receptors. Side effects include drowsiness, dry mouth, and constipation.
- Dapsone (Aczone): An antibiotic that fights inflammation and may help individuals whose hives do not respond to traditional antihistamines, according to Cohen.
- Immunosuppressants: These drugs weaken the body’s immune response and include Cyclosporine, Methotrexate, Mycophenolate Mofetil, and Tacrolimus.
- Omalizumab (Xolair): This injected anti-inflammatory agent prevents your cells from releasing chemicals like histamine believed to trigger hives, says Owens. It is not approved for treating hives other than CSU.
The good news is that CSU usually resolves over time. Nearly half of individuals are hive-free within a year. „Most of the time, we can manage CSU with a bit of trial and error so that patients can continue living their lives with minimal redness and itching, even if they don’t completely disappear,“ says Cohen.