Hives, which can also be called urticaria, are itchy rashes that develop on the skin. They can appear as red welts, large blotches of raised skin, or even as a widespread rash across a portion of the body.

If you’re experiencing hives, you’re not alone either. According to the American College of Allergy, Asthma, and Immunology, roughly 20 percent of people are affected by hives at some point in their lives.

Because hives are a common symptom of an allergic reaction, most people usually see an allergist straight away. However, there are many other reasons you could have hives, and you should consider other causes if an allergy test comes up negative.

Here are four surprising but real causes of hives that you may want to consider. Speak to your doctor about treatment if you suspect any of these factors might be causing your hives.

Hives Trigger #1: Stress

Your body is quite effective at treating illness on its own, but it can sometimes be fooled. When you’re overly stressed, your body’s immune system suffers. This is why you may notice yourself getting sick more often when your stress or anxiety levels are high. Your body knows something is wrong, so it releases histamine into your body in an attempt to get rid of the problem.

Unfortunately, histamine does not stop stress. The first step is to pinpoint the stressors in your life. You may be stressed about work, an upcoming marriage, or any number of other life-changing events. Practice calming techniques, such as yoga or meditation, and see a doctor or therapist for help reducing your stress levels.

Hives Trigger #2: Hormone Imbalances

Although both men and women can experience hormone imbalances, women will likely see this happening once they begin nearing menopause. That’s because menopause causes imbalances between the two most important hormones in a woman’s body: progesterone and estrogen. The medical community is not yet sure why these imbalances cause inflammation, but they are certain there is a connection. Hives are a type of inflammation, and could be a result of menopause nearing. Autoimmune diseases, such as thyroid disease, lupus, and celiac disease, can also cause hormone imbalances that lead to hives. If you suspect you have any of these conditions, speak to your doctor.

Hives Trigger #3: Your Laundry Detergent

Detergents are full of dyes and additives that can easily irritate sensitive skin, especially in kids, and the result can become as severe as developing hives. If you suspect your detergent is causing a problem, try switching to a dye-free, fragrance-free alternative.

Hives Trigger #4: Your Workout Routine

No, you’re not allergic to exercise, but your body might think so. Similarly to daily stress, exercise causes strain on your body and therefore has similar effects. When you work out, your sympathetic nervous system can trigger a histamine response from your body to combat the stress.

Though it may be tempting to continue working out despite the appearance of hives, it’s best to stop and wait about 10 minutes before resuming. If the hives don’t go away, you may need to go see your doctor. Continuing your workout session could lead to a dangerous condition called anaphylaxis, which causes your throat or tongue to swell up and block your airway. Because anaphylaxis occurs quickly and can be life-threatening, it is best to resume exercising only when you’ve been cleared.

Though hives can be annoying, all it usually takes is a look at your lifestyle and daily habits to find the culprit. You could be one step closer to being hive-free today, but always speak with a physician to get a clear diagnosis to avoid any complications.