For a small number of people, though, hives come back again and again, with no known cause. When new outbreaks happen almost every day for 6 weeks or more, it’s called chronic idiopathic urticaria (CIU).
One percent or less of people have it. It’s most common in people between the ages of 20 and 40. With CIU, a single outbreak usually lasts no more than 24 hours. After that, new hives form.
What Causes It?
Experts don’t know. The immune system seems to play a role. Some people get chronic hives at the same time that they get other problems like thyroid disease, hormonal problems, or cancer.
What Are Some Common Triggers?
Even though doctors can’t say for sure what causes CIU, they do know things that can lead to flare-ups. They include:
How Is It Diagnosed?
If you’ve had hives for several weeks and don’t know why, see your doctor.
She’ll want to know:
- When and where they pop up
- How long they last
- Possible triggers
- If you have swelling
- What other symptoms you have
- If you’re taking new meds
She’ll also ask about the foods you eat and if you have pets, to see if an allergy is to blame. She may check for other illnesses or conditions that could be causing the hives, like an overactive or underactive thyroid.
If she can’t find a cause, you’ll likely be diagnosed with CIU.
Is It Contagious?
No. And while it’s itchy and painful, it isn’t dangerous.
How Long Does It Last?
Chronic hives don’t last forever. Most people have them for 1 to 5 years. For a small number of people, it can last longer. There’s no known cure, but medicines and lifestyle changes can help you feel better.