Carol,
It's almost certainly an effect of the nicotine, because a study published in the New England Journal of Medicine, demonstrates that nicotine has a very beneficial effect on UC patients. No one knows exactly how the chemistry involved with this process actually proceeds, but there's no question that nicotine has a significant protective effect on colitis, (though the effect does not apply to Crohn's disease, and may even have a negative effect).
Here is a quote from an article on Ulcerative Colitis:
Smoking has been proposed as a factor contributing to the etiology of this illness. It has now been well accepted that ulcerative colitis is a disease of non-smokers although the direct mechanism is not understood. It is known that a non-smoker or an ex-smoker is at higher risk of acquiring this illness than a current smoker. In fact, this risk is highest in persons who have just recently quit smoking. This finding has led to reasearch involving the use of nicotine in the treatment of acute, active as well as chronic (remissive) ulcerative colitis.
That quote is from the site referenced by the link below. In fact, if you will go there, and scroll down to where you see the phrase, "
An abnormal immune response may cause ulcerative colitis.", in the left column, you can read a very good description of how UC, (and MC, for that matter), is thought to be triggered, in the right column.
http://www.gidoctors.com/Colitis/Colitis.html
Here's a link to the article in the NEJM, concerning the UC research involving transdermal nicotine patches, that I mentioned above:
http://content.nejm.org/cgi/content/abstract/330/12/811
Since UC and MC both appear to be frequently triggered by the act of stopping a long-term smoking habit, I would think that it is very likely that many/most MC patients would also be likely to respond favorably to nicotine therapy, especially those whose disease was apparently triggered by a termination of the use of nicotine. Unfortunately, it might be difficult to find a doctor open minded enough to prescribe this treatment, though I don't see how any risk could be involved, since nicotine is not addictive, when administered by means of a transdermal patch. Though there's a fair amount of information available related to using nicotine to treat UC, I'm not aware of anyone who has experimented with this concept, for the purpose of treating MC, however.
Also, note that both of these articles are over 10 years old, (10/15/98, and 3/24/94). Since there doesn't seem to be much information available from a more current date, I take that to be indicaticative of the unfortunate fact that the medical community is strongly influenced by the concept of "political correctness". IOW, since smoking is considered to be a "politically incorrect" behavior, these days, the medical community has chosen to shun it, and to avoid anything associated with it, and it has chosen to abandon further research that might possibly be of great benefit to many sufferers of colitis.
Tex