I have had UC since 1995 and have been flying as crew since 1996. Throughout that time I have had flare ups from time to time. Some worse than others, thankfully at the moment I am in remission. The condition can come and go with varying severity.
Only once has an airline threatened to not employ me and I successfully argued my case enough for them to withdraw their concern. My current employer allows me to fly as long as I keep them up to date with any change in the condition. (I will admit though it is a worrying time when you fill out the medical questionnaire to see if you're ok or not.)
Steroids are very effective in the short term however large dose ie 25mg+ can affect you when flying in the cabin. You can feel at best almost high at worse very on edge. The problem with steroids is not only are they working on your colon but every other organ in your body too. Blood pressure can really go bonkers and as you know the body works harder when at altitude. For this reason I would advise you to think twice before flying when on a high dose. Fine at lower doses but remember, it's your health. I believe that Steroids are not allowed by the CAA however that is arguably for pilots only. It can be open to interpretation re - Cabin Crew. For this reason one can sympathise why some 'gamble' and don't tell their airline if they are only on the medication for a short period.
What has always frustrated me when dealing with airline doctors and GP's in general is that most of them know only the basics of UC. This does not help when particularly with airline docs, they are responsible for signing you off. Over time you may well find that you will know more than they do about the latest treatments available and how best to manage it. On the other hand most UC specialists know very little about aviation matters, nearly all have rejected any concerns with flying whilst on medication. All I can advise is my own experiences hence my notes on steroids.
I agree with the last post in that modern treatments have really moved on tremendously and with proper management, you should live as normal a life as possible. Be prepared for some nasty flare ups and also for many long periods of remission when you may well feel that your condition has healed. UC is a stubborn so and so and has a habit of waking up when you least expect it.
So my advice to you is be open (to a point) with your airline, do not over complicate matters in telling them too much, take steroids when you absolutely have to but bear in mind what I said earlier. Your specialist will not want you on them forever as they do have not so nice side effects. There are other very effective safer long term treatments he will look at for you. But again, take them in the short term as they do work amazingly well.
A really useful forum is found at
Ulcerative Colitis Information Centre have a look and you will find some brilliantly helpful info here.
Hope that helps, I have had a brilliant career to date and UC has not helped but in no way compromised my career. Stay safe, keep fit, eat well and your career will be as long as you want it to be.
Good luck
PP