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What is A Flare?

Like any form of arthritis, ankylosing spondylitis (AS), comes with good days and bad days. Those times when symptoms increase are called “flares.”

AS is a type of inflammatory arthritis that primarily affects the spine or back bone. So, flares tend to be felt first and most severely in the back or hips. That’s because the joints and ligaments in the back are becoming inflamed (enthesitis). This is what creates the pain, tenderness, and stiffness most often experienced during a flare.1-2

While AS primarily affects the spine, symptoms may also spread to the neck, shoulders, ribs, hips, knees, feet, eyes and bowels. AS is a systemic disease, which means it may affect your organs, including the heart and lungs.

Types of flares

Doctors classify AS flares as:

  • Minor or localized, with pain and swelling centered in one area, usually with some fatigue and stiffness.
  • Major or generalized, which impact the whole body, with more pain, a feeling of hot burning joints, muscle spasms, fever, sweating, extreme fatigue and stiffness.3

Minor flares usually can be handled with additional pain medication, or by trying a new drug for AS. Major flares may interrupt your normal routines and require more aggressive treatment.

Symptoms of AS flares

The severity and combination of symptoms that occur during a flare can vary widely from person to person. Some less common flare symptoms include:

  • Redness, swelling, or a feeling of heat
  • Skin rash
  • Depression, social withdrawal, anger
  • Loss of appetite
  • Uveitis, which is pain, redness, and sensitivity to light in one or both eyes
  • Chest pain

In a study of AS patients in the United Kingdom, 70 percent said they felt they had a flare in any given week. Major flares tend to happen to people with more advanced AS.3

How long does a flare last?

A flare may build gradually or hit suddenly. Sometimes the pain during a flare is mild and comes and goes. At other times, the pain may be severe and constant. A small study of 214 people from the United Kingdom (UK) found that all participants experienced between one and five minor flares per year but only 55 percent had major flares.5

Another small UK study found that major flares lasted an average of 2.4 weeks and tended to be preceded by and followed by minor flares in 92 percent of cases.3

While unpredictable, flares do die down, allowing you to return to your normal life.

What causes flares?

Doctors do not fully understand what causes flares. Sometimes, flares seem to follow infections, high stress situations and “overdoing it.”4-5

Some people learn what triggers their flares and can manage their disease by reducing stress or maintaining their exercise routine, for example. Other people with AS are never able to identify particular triggers.

Treatment for flares

It may take some trial and error to find the treatment that helps you most during a flare. Options include medications, relaxation, gentle exercise, hot or cold packs on inflamed joints, meditation, or sleep.4-5

Written by: Jessica Johns Pool | Last reviewed: March 2019
  1. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Ankylosing Spondylitis. Available at https://www.niams.nih.gov/health-topics/ankylosing-spondylitis. Accessed 3/5/2019.
  2. Spondylitis Association of America. Spondylitis Web Info for Teens. Available at http://teens.spondylitis.org/. Accessed 3/5/2019.
  3. Cooksey R, et al. Frequency and characteristics of disease flares in ankylosing spondylitis. Rheumatology, Volume 49, Issue 5, 1 May 2010, Pages 929–932, https://doi.org/10.1093/rheumatology/kep435.
  4. Arthritis Foundation. Arthritis Flares Are Normal but Still Difficult. Available at https://www.arthritis.org/living-with-arthritis/pain-management/flares/arthritis-flare.php.
  5. Brody S and Calin A. Definition of disease flare in ankylosing spondylitis: the patients' perspective. The Journal of Rheumatology May 2002, 29 (5) 954-958.