Urticaria is the medical term for hives. These are itchy reddish bumps, or welts, on your skin. Your dermatologist may call the bumps wheals.

When the hives last for more than six weeks, they’re called chronic. And when the cause is unknown, they’re called idiopathic.

Hives can be very uncomfortable, interfering with sleep and normal daily activity.

Before classifying hives as idiopathic, your doctor will check for the presence of an allergy or infection. If neither of these is the cause, it may be idiopathic urticaria. About 75 percent of cases of hives are idiopathic.

Chronic hives don’t pose an immediate risk. But the sudden appearance of hives can be a sign of an allergic reaction that could lead to anaphylactic shock. This is a serious condition that can close off the throat and lead to strangulation. Use an EpiPen (a device that injects epinephrine) if you have one, and seek emergency care right away if this happens to you.

Symptoms of chronic idiopathic urticaria include:

  • raised or swollen red welts on your skin (hives or wheals) that last for more than six weeks
  • itching, sometimes severe
  • swelling of the lips, eyelids, or throat (angioedema)

Your hives may change size, fade, and reappear. Heat, exercise, or stress may aggravate your symptoms.

Chronic idiopathic urticaria isn’t an allergy and isn’t contagious. It’s probably caused by a combination of factors. These may include something in the environment that’s irritating you, your immune system, and your genetic makeup. It can also be a response to a bacterial, fungal, or viral infection.

Chronic idiopathic urticaria involves activation of your immune response system. It also affects your nerve hormones and the clotting processes in your blood.

Any of these things may trigger an outbreak of hives:

  • pain medications
  • infection
  • insects or parasites
  • scratching
  • heat or cold
  • stress
  • sunlight
  • exercise
  • alcohol or food
  • pressure on your skin from tight clothing

A thyroid connection

Chronic urticaria may be a symptom of a thyroid problem. This is more common in women.

In one study of people with chronic urticaria, 12 of 54 people, all females, had thyroid (anti-TPO) antibodies in their blood. Of these 12 women, 10 were found to have hyperthyroidism, and were treated for it.

Anti-TPO antibodies may also indicate the presence of an autoimmune thyroid disease, such as Graves’ disease or Hashimoto’s thyroiditis. Your doctor will look for this if your blood test shows raised levels of anti-TPO.

Your doctor will ask you about your medical history and examine you physically. They may order a blood test and may refer you to a specialist for allergy testing.

You may be asked to keep a diary to record what you eat or drink, environmental factors, where the hives appear, and how long they last.

Over-the-counter (OTC) antihistamines (allergy medication) are usually the first-line of treatment for chronic hives.

Nondrowsy antihistamines with few side effects include:

  • cetirizine (Zyrtec)
  • loratadine (Claritin)
  • fexofenadine (Allegra)
  • desloratadine (Clarinex)

If your hives don’t clear up with OTC antihistamines, your doctor may try one or more other types of treatment, including:

  • H2 blockers. These are drugs that block the production of histamines that can cause hives or overproduction of stomach acids. Common versions are ranitidine (Zantac), cimetidine (Tagamet HB), and famotidine (Pepcid).
  • Short-term oral corticosteroids, such as prednisone. These are especially useful for reducing the swelling around eyes, lips, or throat (angioedema) that can accompany hives.
  • Antidepressants, such as doxepin cream (Zonalon).
  • Immune suppressants. These include cyclosporine (Gengraf, Neoral) and tacrolimus (Astagraft XL, Prograf).
  • Monoclonal antibodies. Omalizumab (Xolair) is an expensive, newer drug that has proved very effective against chronic idiopathic urticaria. It’s typically injected once a month.

In one study, 83 percent of people with chronic urticaria had a complete remission after treatment with omalizumab. However, symptoms returned within four to seven weeks after the drug was stopped.

Common foods that produce allergy in some people include eggs, shellfish, peanuts, and other nuts. Spoiled fish can contain a high level of histamines, which may bring on hives.

If you or your doctor suspects that the hives are coming from a food allergy, tests can be carried out to verify this. You may be asked to keep a diary of everything you eat and drink.

Food additives and salicylic acid (contained in aspirin) have been shown to bring on hives in some people. Aspirin and other nonsteroidal anti-inflammatories have been reported to worsen outbreaks of hives in 20 to 30 percent of people with chronic urticaria.

Chronic idiopathic urticaria is an unpleasant condition, but it’s not life-threatening. Treatment with antihistamines or other medications will usually clear it up. But it may reappear when treatment is stopped.

You should see your doctor if you have a severe case of hives, or if they last for several days.