Several factors, including environmental risk factors, may play a role in triggering ulcerative colitis flares, during which symptoms return or worsen.

Ulcerative colitis (UC) is a chronic condition that causes inflammation in the colon and rectum.

During flares, people typically experience symptoms such as diarrhea and abdominal pain. A period of remission often follows a flare.

Although the exact cause of UC remains unclear, several factors, including environmental ones, can trigger flares and worsen symptoms. By understanding the environmental factors that can trigger a flare, a person may be able to prevent flares and reduce symptom severity.

Dr. Ashkan Farhadi, a gastroenterologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA, spoke with Medical News Today about different environmental factors and how they may affect people living with UC.

This article also reviews current studies related to environmental factors that can affect a person’s UC symptoms.

A person’s environment may expose them to risk factors that can aggravate or potentially cause UC flares.

Although everyone responds differently, some common environmental triggers include:

  • diet
  • infections
  • exposure to pollution
  • stress
  • use of certain medications
  • surgeries


The Crohn’s & Colitis Foundation notes that an infection may be the triggering event that causes UC to occur.

In a 2021 study, researchers found that the rate of common infections, including Salmonella, Campylobacter, and Clostridioides difficile, is higher among people living with UC.

However, Dr. Farhadi pointed out that although bacterial infections from Salmonella and Campylobacter have an association with UC, “we can’t say it’s causation.”

Dr. Farhadi also noted that if a person has a C. difficile infection, they will experience flares that do not respond to treatment. A person will need to receive treatment to get rid of the infection before they can “bring the disease into remission.”

A person should remain vigilant for signs of infection, particularly when using corticosteroids, biologics, or immunotherapies.


Smoking can lead to many health consequences, but UC does not appear to be one of them. Studies have actually shown weak evidence that smoking may reduce the severity of UC.

Experts do not fully understand the protective effect of smoking on UC, but nicotine may play a role. According to the Crohn’s & Colitis Foundation, nicotine may protect against UC by:

  • increasing the production of mucus in the colon and rectum
  • suppressing the immune system and preventing inflammation in the colon
  • releasing nitric oxide, which may reduce muscle activity in the colon

According to a 2020 review, transdermal nicotine, or nicotine patches, may have some benefit when people with mild to moderate UC use them alongside traditional treatment. However, transdermal nicotine may cause side effects, such as:

  • nausea
  • lightheadedness
  • difficulty sleeping

Dr. Farhadi noted that “quitting smoking can cause UC to flare, but the benefit of quitting outweighs the risk of flares.”

The health benefits of quitting smoking include:

  • improved overall health
  • increased life expectancy
  • lower risk of cancer
  • lower risk of heart disease and stroke

In other words, people who smoke should still consider quitting even if doing so causes their UC symptoms to flare.


Certain medications may trigger flares in a person’s UC symptoms. These medications include nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen (Advil), and naproxen (Aleve). Some antibiotics may also trigger flares.

In addition, people using medication for their UC may experience flares if they do not take it consistently.

Lack of exercise

Regular movement can benefit a person’s overall health in several ways, and it may also help improve or prevent UC symptoms.

According to Dr. Farhadi, “Regular exercise [can help] to manage your stress.” His advice is to go on daily walks “[for a] minimum of 30 minutes, at your fastest pace that is possible and practical without jogging.”

This type of exercise can boost cardiovascular fitness, manage body weight, improve sleep, and also reduce stress.


Stress can worsen the symptoms of UC.

Dr. Farhadi said that several of his patients have reported psychological stress and flares occurring around the same time. He added that divorce, final exams, job interviews, and other stress-inducing events may trigger UC symptoms.

He recommended that people with UC work to improve their stress management so that they can better handle stressful situations. In addition to exercise, he suggested mindful meditation.

Sleep hygiene

Sleep can play a role in preventing or reducing the severity of UC flares.

According to Dr. Farhadi, a person should plan to follow a “consistent sleep hygiene” routine on at least 6 days of the week. Doing so can help minimize UC flares.

Some tips for improving sleep hygiene include:

  • removing all electronic devices from the room
  • sleeping in a darkened room at a comfortable temperature
  • going to sleep and waking up at a consistent time
  • avoiding alcohol, caffeine, and large meals before bed
  • participating in regular exercise

Air pollution

According to a 2019 review of studies, air pollution may play a role in the development of UC. The researchers looked at children’s home environments and noted that children who grew up with constant or regular exposure to air pollutants had an increased rate of developing UC.

Diet and food additives

Dr. Farhadi noted that diet can play a role in helping a person living with UC, but he also stated that no studies have proven that one diet is better than another when it comes to UC.

Instead, he suggested that people “listen to their gut.” In other words, if a food bothers them, they should avoid the food altogether. He also said that people with lactose intolerance may experience flares in their UC symptoms when consuming dairy.

Some studies also list soft drinks as a risk factor for UC flares.

Along similar lines, some people may find that exclusion diets help their UC symptoms. Research indicates that many people living with UC eliminate troublesome food.

The study authors do not recommend any specific exclusionary diet, but they advise that people living with UC eat more homemade foods. By doing so, they can avoid food additives, such as sugar and salt, which could cause flares.

Researchers still do not know the exact cause of UC. However, they do know that certain factors, including a person’s response to their environment, may play a role in the development and severity of UC.

The following are possible causes that need further investigation:

  • Autoimmune condition: The immune system attacks healthy cells and causes long-term inflammation in the colon.
  • Genetics: The condition may pass from one generation to the next.
  • Changes in microbiome: The digestive tract is home to billions of bacteria, fungus, viruses, and other microorganisms that play a role in various bodily functions, including digestion.
  • Environmental triggers: These may cause symptoms to appear or worsen.

Exposure to a virus or bacteria may trigger an immune response. In cases of UC, the resulting inflammation persists for a long time after the infection has already passed.

Many other conditions have poor living conditions among their risk factors. In contrast, Dr. Farhadi describes UC as a “disease of wealthy nations.”

A 2019 study backs up his statement. The authors note that people living in more affluent countries in Europe and America have higher case numbers of UC. This may be due to a reduction in exposure to certain infections that are more common in areas with inadequate plumbing.

The study also suggests that certain factors may help prevent UC. These include:

  • breastfeeding or chestfeeding
  • minimizing exposure to air pollution
  • avoiding soft drinks
  • having high levels of vitamin D
  • drinking tea
  • exercising regularly

A person should take note of their environment and how their UC symptoms respond to different stimuli.

It may be helpful to remove foods that cause symptom flares from the diets. In addition, individuals can try:

  • using stress management techniques
  • partaking in regular exercise
  • improving their sleeping habits, if necessary

Several environmental factors can play a role in triggering UC flares and symptom severity. These include air pollution, medications, stress, diet, infections, exercise, and sleep habits. No single approach will work for everyone, but people living with UC may find that taking steps to control their environment helps them reduce the severity and frequency of their flares.