Causes of Ulcerative Colitis


The causes of Ulcerative Colitis are a contentious issue, this is due to the fact that it's very difficult to pin down the exact starting point of the disease. The medical profession is currently unable to give an underlying reason (research will hopefully change this). Many UCers feel that they know what caused the disease to kick in, even if they don't know the reason why they're susceptible. Please bear in mind that this page is based on the experience and knowledge of UCers.

Ulcerative Colitis has no known cause

Say that again? Ulcerative Colitis has no known cause!! Remember we're talking about the reason behind the disease developing in the first place - not the causes of a Colitis flare-up! It's easy to get the two mixed up.

So if we don't know what causes Colitis, how do we cure it? Well that's the billion dollar question and the reason why Colitis sufferers are said to be in remission as opposed to cured. Currently, there are differing theories as to why a person might develop Colitis, but because of the number of possible influences, they are only theories.

Research has shown that Colitis can be hereditary and that certain groups of people are more susceptible as are certain areas in the world. But it isn't exclusive, anyone can develop colitis.

Enviroment versus Genetics

For some, the belief is that Colitis sufferers have an underlying genetic disorder. This means the immune system is the weak link, but the genetic disorder can't be altered e.g. an Ulcerative Colitis sufferer will always get Colitis, no matter what.

However, because many enviromental factors play a huge role in genetic development, it's not as clear cut - as demonstrated in the case of the UCers that developed Colitis through drinking unclean water.

In fact, research seems to suggest that in the case of autoimmunity, the ratio of enviroment to genetic probability is 70% to 30%. Information that I've read on automimmunity says that genes can be switched on or off, and that enviroment can be the trigger. In that respect, the two go hand in hand. However, if your enviroment is healthy, the switch should stay off.

Each case is different - one answer doesn't fit all!

Funnily enough, although a definitive underlying cause has yet to be discovered, you will find many people (including those in the medical industry) who will tell you point blank what doesn't cause Colitis (and flare-ups). Personally I find this strange, because if you can't definitively say what causes it, I'm not sure how you can rule anything out?

There are so many possible influences it seems naive for anyone to state that they have a definite answer relating to the disease. To underline how individual the disease is, take a look at some Colitis forums - you'll discover that every single case is different.

So I would say beware of anyone who tells you the cause of Colitis, they often go on what they've learnt from one source. Some get offended if you don't agree with their point of view, but unfortunately Colitis is far too individual for one point of view to apply to everyone. It's best to keep an open mind when hearing different opinions or perspectives, because there might just be something in them that helps alleviate our own symptoms.

It's worth mentioning that there's a whole area of treatment, called 'functional medicine' that's been treating automimmune diseases such as Ulcerative Colitis for years. Functional medicine looks at the overall lifestyle of the sufferer to establish the cause and then design a specific treatment for each patient.

This area of treatment is seen as suspicious by 'conventional' medicine although interestingly, some areas of functional medicine are creeping into the 'mainstream'. Personally, I'm interested in anything that can benefit Ulcerative Colitis and I don't judge it on someone elses opinion. I look into it myself because you never know where you might find something that benefits your situation.

Impromptu Survey

I've seen the question: "what caused your colitis?" asked a lot in Ulcerative Colitis forums. A while ago, on a Colitis Facebook page, I decided to pose the question: "can anyone put the start of their colitis down to something concrete?" There were quite a lot of replies so I worked out the percentages from the reasons given.

The results were:

  • Smoking 39%
  • Stress 34%
  • Food Poisoning 11%
  • Misc 11%
  • Pregnancy 5%

In my case, I believe (although it's only a hunch because of the number of variables) stress and bad diet caused my colitis (antibiotics could have been another possible trigger).

Most of the answers in the survey above could affect the immune system (70% of which is based in the gut).


I thought this cause should be first because it affects everyone.

Discussions and anecdotal cases in many different IBD forums would suggest that stress can play a big part in the reason Ulcerative Colitis starts, and definitely plays a part in flare ups.

If you read a lot of colitis forums you will find that many UC sufferers have experienced periods of extreme stress which has coincided with the start of their first UC symptoms.

It's worth noting that both mental and physical stress can be a cause. In various forums I've seen whole threads where colitis sufferers are discussing how their symptoms started after they'd been involved in an accident.

Because there are no signs of colitis in my family, I'm convinced stress was the main reason that UC started for me. I suffered from panic attacks and anxiety for years; thankfully not so much now. However, scientific studies show that continuous stress and anxiety cause a change in bacterial and mucosal interactions as well as a measurable decline in the immune system's ability to fight disease.

A study way back in 2005, that looked at lots of research that had been done on stress and IBD concluded:

In recent years considerable evidence has accumulated that psychological stress does indeed contribute to the risk of relapse in IBD. Furthermore, laboratory research has indicated a variety of mechanisms by which stress can affect both the systemic and gastrointestinal immune and inflammatory responses.

The main points taken from their study of psychological stress in IBD were:

  • Recent studies indicate that chronic stress, adverse life events, and depression can cause relapse in patients with IBD.
  • The effects of stress on inflammation in IBD are likely to be bought on by:

    • changes in hypothalamic-pituitary-adrenal (HPA axis) function
    • alterations in bacterial-mucosal floral interactions
    • activation of mucosal mast cells
    • peripheral release of corticotrophin releasing factor/hormone (CRF or CRH) - a peptide involved in the stress response.

      In the short term, CRH can suppress appetite, increase subjective feelings of anxiety, and perform other functions like boosting attention. Although the distal action of CRH is immunosuppression via the action of cortisol, CRH itself can actually heighten inflammation
  • The symptoms of IBD may be exacerbated by the effects of stress on gut motility and fluid secretion.
  • There is a need for further controlled studies of the potential benefits of stress reduction therapy in IBD.


I've never smoked so this is something I can personally rule out. However, you will find many threads where UCers ask about giving up smoking or continuing smoking because it affects their colitis.

It is a fact that continuous smoking damages immune cells and decreases their ability to heal. Just reading that sentence makes it easy to understand how smoking could bring on colitis. It would probably be after some years of smoking which is one reason why it may not get linked to colitis.

A strange phenomenom of smoking is that giving up can actually increase colitis symptoms for some UCers! This is something I've read a lot in the colitis forums; some smokers that suffer from colitis decide to quit smoking only to find that their symptoms get worse. Some of them decide to take up smoking again because it eases the symptoms.

Food Poisoning

This cause, of all the responses in the survey, potentially makes the most sense as to why colitis could start. The digestive system is ravaged by a bacteria or virus on or in the food, which effects the balance in the colon and brings on colitis.

Someone with a weaker immune system is more susceptible to food poisoning, just as food poisoning can weaken the immune system.


Some answers were unique, hence this category. Reasons given as to why UCers believed their colitis started included:

  • Liver problems
  • After having a tattoo
  • Emergency cesarean
  • Being rundown with infections for a period of time
  • A sickness bug


A reason that's easier to pinpoint!

Pregnancy lowers the immune system so that the body doesn't fight off the 'foreign body', for want of a better phrase. This then, could well be the starting point behind the onset of colitis.


This cause isn't on the list but there are UCers who have developed colitis because it's in their family; the medical profession agrees that this can be a cause of colitis.

pH levels

This is something I hadn't really considered until speaking to a friend about their colitis. They had cut out the acidic side of their diet and seen great results. I've also read about some UCers drinking Baking soda to balance their pH levels with some success on their colitis symptoms.

Of course, these UCers had already developed colitis but there's a growing opinion by some Doctors, Specialists and Nutritionists, that an acidic diet over a long period time can lead to many of the major diseases known today. When you look at the list of foods that fall into the acidic pH levels, it doesn't take a great leap of imagination to see that this theory makes a lot of sense.

More info on pH levels


Antibiotics are known to cause Colitis in some because of the way they alter the balance of bacteria in the intestines. Antibiotics (as opposed to probiotics) indiscriminately kill most of the bacteria (good and bad) along the intestinal walls. For some people this can lead to a proliferation of certain bacteria that were previously outnumbered before taking antibiotics.

If the bacterium Clostridium difficile multiplies, it can lead to toxins being released, which is one of the ways the colitis called C-Diff can develop. It is the release of the toxins that damage the intestinal wall, not the bacteria itself.

The taking of probiotics to balance antibiotics is something I often see discussed in Colitis forums and groups. I've seen it said that there's no point taking probiotics whilst on a course of antibiotics because they will kill the good bacteria.

However after reading about it, the suggestion seems to be that it's actually a good idea to take probiotics, but you should wait until a couple of hours after taking antibiotics. This gives a chance for the antibiotics to pass through before you replenish the intestine with 'good bacteria'.

The benefits of this are that you're adding good bacteria daily, which should lessen the chance of the digestive system becoming upset by a longstanding microbial imbalance.

More info on probiotics

Unclean Water

Recently I read a very interesting post by a UCer who developed Ulcerative Colitis after drinking 'unapproved water'. The reason he (along with others) drank the water is because they were part of a unit serving in a hot country and were told the water had been 'approved'.

It turns out that after drinking the water, they were informed it hadn't been approved. Beforehand he'd noticed the water had a smell, but because dehydration is an issue and they were given the all clear, everyone drank it

So the upshot was that everyone developed stomach bugs and diarrhea, but three remained ill whilst the rest eventually recovered. Those three developed Ulcerative Colitis with all its symptoms. This then, is a clear indication that unclean water was the cause of Colitis in this case.

I was interested to know the health history of those that developed UC and those that didn't, to see if there were any distinct differences e.g. did the three have a lowered immune system at the time of drinking the water for example?

I asked this question on the thread and the answer was no, they didn't have any cold or illness at the time although interestingly, the UCer reported that something all three of them have in common are stomachs sensitive to foreign foods (they had all been stationed in different countries at certain times).

However, without questioning the entire unit we don't know whether any of those that didn't develop colitis also had sensitive stomachs to foreign food.


Perhaps the case of 'unlcean water' helps back-up one of the main theories behind the cause of Colitis - Genetics. The theory is that it could be a genetic abnormality which makes certain people susceptible to Colitis. This predisposition could mean Colitis develops depending on the enviroment encountered by the person. Enviroment can encompass many things - diet, location, living conditions, lifestyle etc, etc, etc.

So with genetics in mind, in the case of unclean water above, the three that developed Colitis would be said to have a genetic predisposition to problems involving the colon or digestive system.

However, this doesn't mean the develpment of colitis would be a certainty during the lifetime of the three. It suggests that if only two of the three had drunk the unclean water, one of them would not have developed Colitis at this point. They may well have developed it at some point in the future, but because enviroment is a factor, it's not a certainty.

After reading different sources of information about autoimmune disease, a general consensus appears to be that the cause ratio of the disease is about 70% enviroment and 30% genetic. I often see enviroment called a 'trigger'. The theory says that our enviroment (for example: stress, smoking, toxins in our diet; toxins we breathe in or touch, etc.) can alter certain genes, which in turn, can trigger the autoimmune disease process.

The positive spin on this point of view is, if there's a trigger that turns on the autoimmune process, then it may be possible to turn the trigger off. Something the Leaky Gut protocol is based on for example.

Leaky Gut

I only learnt about Leaky Gut fairly recently, although I'd heard the term for some time. It would appear that it's directly related to autoimmune disease and therefore, Ulcerative Colitis.

It's not actually recognised as an 'official' ailment, but treatment has been successful for many, and research is ongoing into the various symptoms, causes and effects related to it.

The term 'Leaky Gut' is really a summary of the consequences of a compromised intestinal barrier, to which there can be numerous causes. However, because a compromised intestinal barrier can ultimately lead to autoimmune disease, it should be taken seriously.

More information on leaky gut