If you’ve ever had hives, you know that these red, itchy welts can be very uncomfortable. Usually, hives, also known as urticaria, go away on their own. But sometimes they last for weeks or months and doctors can’t find a cause. When this happens, it is known 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 particular allergen or specific triggers like cold or sun exposure,” says Jeffrey Cohen, MD, a dermatologist at the Yale School of Medicine. “CSU can last for months or even years, although it usually eventually resolves on its own.”
Hives themselves are common. An estimated 20% of all Americans will experience it at some point. CSU is much rarer. Less than half of 1% of all people in the United States have ever had it. It occurs most often in adults between the ages of 20 and 40, and women are twice as likely to have CSU than men.
What does CSU look like?
CSU looks like any other hives: patches of red or skin-colored welts (wheals) that can appear anywhere on the body, says Michael Cameron, MD, assistant professor of dermatology at Mount Sinai Health System in New York. They are usually itchy and can vary in size and shape. They usually disappear within 24 hours. But unlike acute hives, they often recur, with entire episodes lasting longer than six weeks. There is also no known trigger.
“Sometimes, when health care providers take a careful history, patients may realize that their hives are due to exposure to the sun or water or to the pressure of a heavy bag or seat belt for several hours,” says Cameron. “But for patients with CSU, the source of their hives is a mystery.”
Many people with CSU also develop a condition called angioedema. This is bags and swelling in places such as your lips, cheeks, eyelids, hands or feet.
What causes CSU?
CSU’s hives have no apparent cause. “Chronic spontaneous urticaria was previously known as chronic idiopathic urticaria, which means we don’t know exactly what causes it,” says Cohen.
Usually, if your hives last more than six weeks — even if they come and go — your doctor will refer you to a specialist like an allergist or a dermatologist for more specific testing, says Tiffany Owens, MD, an allergist at Wexner Medical Center from Ohio State University in Columbus. This includes a physical exam at their office and blood tests such as:
- Thyroid hormones. About 30% of the time, people with CSU also have Hashimoto’s disease, an autoimmune disease that causes your thyroid gland to not produce enough hormones. “If you treat the Hashimoto’s, the hives themselves usually go away completely or at least improve,” says Owens.
- Erythrocyte sedimentation rate (ESR). This looks at the level of inflammation in your body. If your ESR is high, you may have an autoimmune disease that causes hives. “One theory is that CSU is an autoimmune disease in which your immune system attacks your own allergy cells,” Owens explains.
- Hepatitis. Sometimes hepatitis B or C can cause CSU, says Owens.
They may also want to do a skin biopsy, where they remove a small piece of skin and look at it under a microscope. This is often recommended if your CSU occurs along with other symptoms, such as fever, pain, hives that last for days, or hives that cause bruising.
Your doctor may run all these tests and find no obvious cause. In this case, they will likely only focus on treating the hives.
Is CSU treatment different?
If your doctor thinks you have CSU, they will still often start you on the same medications they would recommend for acute hives — over-the-counter (OTC) antihistamines — but at a different dosage.
“If you have acute urticaria, your doctor may recommend that you take an over-the-counter antihistamine such as cetirizine (Zyrtec) or loratadine (Claritin) as needed to treat itching,” says Cohen.
But at CSU, the emphasis is on taking high levels daily to prevent urticaria from even emerging. Your doctor may have you take three to four times the recommended amount each day while monitoring you closely for side effects such as dry mouth and nausea.
If that doesn’t work, your doctor may try other medications, such as:
- H2 blockers. Like other antihistamines, these prevent the substances that cause itching and hives from attaching to receptors in certain types of cells. They use heartburn medications such as cimetidine (Tagamet), famotidine (Pepcid), and ranitidine (Zantac).
- Corticosteroids. Medicines such as prednisone can relieve swelling and itching. But you won’t use them for long because they can have serious side effects over time.
- Leukotriene modifiers. Drugs such as montelukast are often used to treat asthma and allergies, but can also help with CSU.
- Doxepin (Silenor). This antidepressant also ensures that histamines do not attach to receptors. Side effects include drowsiness, dry mouth and constipation.
- Dapsone (Aczone). This is an antibiotic that also fights inflammation, Cohen says. Small studies show that it may help people whose hives have not responded to traditional antihistamines.
- Immunosuppressants. These medications reduce the strength of your body’s immune system, Cohen explains. They include cyclosporine (Gengraf, Neoral, Sandimmune), methotrexate (Rheumatrex, Trexall), mycophenolate mofetil (CellCept, Myfortic), and tacrolimus (Astagraft XL, Prograf, Protopic).
- Omalizumab (Xolair). This is an injected anti-inflammatory that keeps your cells from releasing chemicals like histamine that are thought to cause hives, says Owens. It is not approved for the treatment of types of hives other than CSU.
The good news is that CSU is usually not permanent. Almost half of people are hive-free within a year.
“Usually, with a little trial and error, we can get CSU under control so that even if it doesn’t go away completely, patients can continue to live their lives without too much redness and itching,” says Cohen.