Let’s Talk Triggers: What Can Cause a Flare-Up in Ulcerative Colitis?

Jacki McEwen-Powell
Jul 14
10 min read

Introduction

Flare-ups can feel like your body turning on you without warning. One minute, things feel manageable. Next, you're hit with cramps, urgency, fatigue, or all three at once, and you’re left wondering, what did I do wrong?

If you’ve ever spiralled down that rabbit hole, trying to retrace every bite of food, every stressful moment, or every missed hour of sleep, you’re not alone. Trying to figure out what triggered your flare can feel like detective work with an uncooperative witness: your own gut.

I’m someone who lives with UC and has spent years learning how to read my body’s signals, with plenty of missteps and mysteries along the way. This blog isn’t here to hand you a perfect flare-up formula. But it might help you spot a few common threads that could be woven into your own experience.

Because while flare-ups aren’t always predictable, some of them are nudged, or sometimes shoved, into motion by certain triggers. And learning what those might be (for you) can be an empowering step in building a better relationship with your body.

So let’s talk about the things that can cause a flare-up. Not to scare you. Not to blame you. But to gently guide you toward clarity, one piece of the puzzle at a time.

What Exactly Is a Flare-Up?

If you’re living with Ulcerative Colitis, you probably know the word “flare” all too well. But what does it actually mean?

A flare-up is a period when your UC symptoms suddenly ramp up, more bowel movements, more urgency, more blood or mucus, and more fatigue. Sometimes all at once. Sometimes one at a time. Sometimes worse than last time. Sometimes… different. That unpredictability is part of what makes flare-ups so tough.

Flare-ups are the opposite of remission. In remission, your gut is relatively calm. You might still have some symptoms, but they’re more manageable, and inflammation is low or undetectable. During a flare, inflammation kicks up again, and your immune system starts attacking your colon lining, causing all the chaos.

And here’s something important to remember: having a flare-up doesn’t mean you failed. It doesn’t mean you’re not trying hard enough, or that you caused this. UC is a chronic condition. Flare-ups can happen even when you’re doing “everything right.”

Still, there’s power in understanding what might tip the balance. That’s where identifying your potential triggers comes in, not as a cure-all, but as a tool in your UC toolbox.

Common Triggers That May Cause or Contribute to a Flare-Up

Flare-ups don’t always play fair. Sometimes they arrive with no clear warning. Other times, they seem to show up after just one more cup of coffee, a missed dose of meds, or a particularly stressful week.

While it’s true that Ulcerative Colitis can flare for reasons we don’t fully understand, many people with UC begin to notice patterns over time, things that make their symptoms worse or seem to light the fuse.

Let’s explore some of the most commonly reported triggers. Not all of these will apply to you, and that’s okay. The goal isn’t to eliminate everything on this list. It’s to help you get curious and tuned in to your body’s signals, not fearful of them.

1. Stress and Emotional Turmoil

We know it. We feel it. And still, it’s wild how many times stress sneaks up on us, only to show up again in our gut.

The connection between emotional stress and gut symptoms isn’t just anecdotal. Research has shown that the gut and brain are constantly communicating through something called the gut-brain axis. When stress hormones spike, inflammation can increase, digestion can slow down or speed up, and your immune system can become more reactive, basically, a recipe for a flare.

And here’s the kicker: even “good” stress can have an impact. Moving house, planning a wedding, a new job, exciting, yes, but also potentially triggering. Same goes for chronic stress, the kind that simmers under the surface for weeks or months.

You won’t be able to eliminate stress completely (if only!). But you can find tools that help you regulate. Whether that’s walking, journaling, therapy, meditation, or setting boundaries, anything that helps your nervous system feel a little safer can make a difference.

2. Certain Foods and Drinks

Let’s be clear: food does not cause UC. But for many people, certain foods and drinks can make symptoms worse during a flare, or even contribute to triggering one.

The most commonly reported culprits?

Dairy (especially during flares)
Spicy foods
Alcohol
Caffeine
High-fibre foods like raw vegetables, nuts, and seeds
Greasy or ultra-processed meals

That said, food triggers are deeply personal. What sets one person off might be completely fine for someone else. That’s why strict elimination diets without guidance can sometimes do more harm than good.

The aim isn’t restriction, it’s information. If something consistently causes symptoms, it may be worth flagging. But unless you’ve been advised by a dietitian or doctor, there’s no need to cut out entire food groups out of fear.

3. Medication Changes or Missed Doses

UC medication can feel like a lifeline when it’s working, and easy to question when it isn’t. But skipping doses, stopping early, or changing medications without guidance can disrupt your remission and contribute to a flare.

It’s tempting, especially when you’re feeling better, to think: Maybe I don’t need this anymore. But many UC treatments are designed for maintenance as well as symptom control. Going off them suddenly, even something as simple as a missed dose, can lead to a return of inflammation.

If your medication isn’t working or the side effects are hard to handle, it’s worth talking to your doctor. There might be alternative options, but making changes solo can sometimes backfire.

Your treatment plan should work with you, not against you, and that includes building something sustainable over time.

4. Antibiotics

Antibiotics are sometimes necessary, but for people with UC, they can be a bit of a double-edged sword.

While they’re brilliant at wiping out harmful bacteria during an infection, they can also wipe out the good guys. These beneficial bacteria help keep your gut lining happy and your immune system balanced. This disruption to the microbiome can lead to increased inflammation and trigger symptoms, even in people who’ve been in remission.

If you’re prescribed antibiotics, it’s a good idea to let your doctor know you have UC, and ask whether a probiotic (or postbiotic) might be helpful alongside. Not all probiotics are created equal, but in some cases, they may help rebalance things after a course of antibiotics.

You don’t have to avoid antibiotics at all costs; you just need to be mindful and prepared.

5. Infections (Even Just a Cold or Stomach Bug)

Ever catch a cold and notice your UC symptoms flaring too? You’re not imagining it. Even mild infections, like a virus or food poisoning, can trigger your immune system and spark gut inflammation.

Sometimes the infection isn’t even in your gut, but your body still reacts as if it were.

After any illness, try to rest, stay hydrated, and stick to gentle foods. And if things don’t settle within a few days, check in with your doctor to rule out anything more serious, like C. difficile, which can mimic a flare.

6. Hormonal Shifts

For many women, hormones and UC symptoms are closely linked. Maybe you’ve noticed your gut acting up around your period, or that pregnancy, birth control, or menopause seemed to change your symptoms entirely.

Hormonal fluctuations, especially in oestrogen and progesterone, can influence gut motility and inflammation levels. This means your cycle isn’t just affecting your mood or energy levels; it could be part of what’s going on in your gut, too.

Some people experience flares around ovulation or menstruation, while others find their symptoms improve during pregnancy but worsen postpartum. There’s no one-size-fits-all here, but it helps to track your cycle alongside symptoms to see if there’s a connection.

7. Travel or Disrupted Routine

A holiday sounds like it should be relaxing. But for many people with UC, travel can be surprisingly triggering, not because of the destination, but because of what comes with it: new foods, different water, strange sleep schedules, time zone shifts, jet lag, skipped medications, and stress (even the good kind).

Whether you’re camping for the weekend or flying across the world, disruptions to your usual rhythm can throw your gut off balance.

Planning ahead can go a long way. That might mean:

Packing snacks you know your body handles well
Taking medication reminders seriously (set alarms!)
Drinking bottled water if you're unsure of local sources
Building in downtime so your nervous system doesn’t hit the panic button

You don’t have to be hyper-vigilant, but a little preparation can go a long way toward making travel less risky, more enjoyable.

8. Smoking (and Quitting Smoking)

Here’s a strange one: Quitting smoking can actually trigger a flare in some people with UC.

Nicotine appears to have an anti-inflammatory effect on the colon, which might explain why some people experience their first flare after quitting or switching to vaping. That doesn’t mean smoking is “good” for you; it’s still a major health risk, but it’s helpful to know, especially if your symptoms started or worsened after you stopped.

If you're planning to quit, speak to your doctor. There are ways to support your gut through the transition and make that step safer.

9. Lack of Sleep

Sleep isn’t just about feeling rested. It’s when your body repairs and your immune system recalibrates.

Poor or disrupted sleep can raise inflammation and sometimes trigger a flare. Whether it’s a newborn, late-night scrolling, or stress-induced insomnia, it all adds up. You don’t need perfect sleep, but gentle habits like screen-free wind-down time or a consistent routine can help set the stage for better rest.

10. No Obvious Reason at All

This might be the hardest “trigger” to accept, because sometimes, there isn’t one.

Flares can happen without a clear cause, and that doesn’t make them any less real. The immune system, microbiome, hormones, and stress all interact in ways we don’t fully understand yet.

So if none of the usual culprits apply, please don’t turn that into blame. Your body is going through something hard. You’re doing something hard, and even without a clear “why,” you still deserve rest, support, and care.

[Related blog: Are Flare-Ups Random or Predictable]

How to Track Your Own Triggers

When you’re living with Ulcerative Colitis, patterns aren’t always obvious, especially in the thick of a flare. But over time, many people begin to notice that certain symptoms tend to follow certain events, meals, or stressors.

That’s where tracking comes in.

But let’s be real: tracking can be a double-edged sword. If it starts making you feel anxious or hyper-focused on every little sensation, it might not be helpful in that season. This is meant to be a tool, not a test.

What to Track

If you do feel ready to start tracking, here are a few things that can be useful to note:

Symptoms: Urgency, pain, bleeding, frequency, fatigue, etc.
Food & Drinks: What you ate and drank (without judgment).
Stress Levels: Was it a tough day emotionally? A big deadline? An argument?
Sleep Quality: How many hours? Restless or restful?
Medication: Did you take everything as prescribed?
Exercise or Movement: Even a walk can affect how your gut responds.
Menstrual Cycle: For those who menstruate, this can provide valuable context.

You don’t need a fancy app or colour-coded spreadsheet. A simple notebook works beautifully. Even just jotting a few bullet points in your Notes app at the end of the day can be enough.

How Long to Track

Patterns don’t usually reveal themselves overnight. Try tracking for a few weeks, especially around times when symptoms are changing. Over time, you might start to spot things like:

“I always seem to flare the week after my period.”
“Dairy gives me cramps, but only when I’m already run down.”
“Big social events drain me more than I thought.”

And sometimes, the pattern might be: there is no pattern. That’s valuable to know, too. It means you can gently let go of the pressure to control every variable.

If You Think You’re in a Flare…

That sinking feeling when symptoms return, urgency, blood, pain, exhaustion, is one many of us know too well. Whether it creeps in slowly or hits you overnight, the question comes fast: Is this a flare? And what do I do now?

First things first: take a breath. You haven’t failed. You’re not back at square one. There are things you can do to get through this.

1. Check in With Your Doctor or IBD Team

Even if you’ve ridden out flares before, it’s always worth letting your healthcare provider know what’s going on. They might want to run some tests, adjust your medication, or rule out infections like C. difficile, which can mimic a UC flare but needs very different treatment.

You don’t need to wait until things are unbearable. If something feels off, speak up.

Healthline: Ulcerative Colitis Emergency Situations and What to Do

2. Don’t Stop Medication Without Guidance

It’s tempting to experiment when things get intense, skip a dose, double up, or stop everything altogether. But some medications need to be tapered, and stopping cold turkey can sometimes make things worse. Talk to your doctor before making any changes.

If your current plan doesn’t feel like it’s working, you’re allowed to say that. You deserve a treatment plan that makes sense for your body and your life.

3. Rest, Hydrate, and Simplify

When your gut is inflamed, even getting through the day takes extra energy. Give yourself permission to rest. Drink fluids. Eat gently, things like soup, mashed potatoes, rice, or poached chicken.

Gentle movement, heat packs, and loose clothing can make a world of difference, too.

4. Ask for Support

This isn’t the time to go it alone. Whether it’s asking someone to bring you groceries, checking in with a support group, or just texting a friend who gets it.

Your body is doing something hard. You deserve support.

Final Thoughts

Learning to live with Ulcerative Colitis means learning to live with uncertainty. Flare-ups can feel random, disruptive, even scary and trying to figure out what caused them can sometimes feel like a full-time job.

But here’s what I’ve come to believe: the goal isn’t perfect control. It’s self-awareness. It’s learning to listen to your body’s whispers before they turn into screams. It’s having a few tools and insights you can lean on when things get shaky.

Not every flare will have a neat explanation. And not every trigger is something you can avoid. But that doesn’t mean you’re doing it wrong. It means you’re living with something complex. Something that requires curiosity, care, and a whole lot of compassion for yourself.

One step, one flare, one pattern at a time, you’re learning how to live with this. That counts for something. Actually, it counts for a lot.

FAQs

Can stress alone trigger a flare-up?

Stress isn’t the only factor, but it can tip the balance. Emotional and physical stress can influence inflammation and gut function, so it’s worth paying attention to.

Do I need to cut out all potential trigger foods?

Not at all. Everyone’s triggers are different. The goal is to notice patterns, not eliminate everything. Restrictions without reason can cause more harm than good.

I’m flaring but haven’t changed anything. Why?

Sometimes, there’s no clear trigger. That doesn’t mean you’ve done something wrong. Flares can happen even when everything seems “under control.”

Can quitting smoking make UC worse?

In some cases, yes, temporarily. Nicotine has an anti-inflammatory effect in UC. If you’re quitting, talk to your doctor about how to support your gut during that time.