Whenever the subject of trigger avoidance comes up with rosacea usually avoiding spicy food is mentioned. This is due to a 1999 survey conducted by the NRS that is usually referred to as the source of information. How was the survey conducted?
This was not a placebo controlled, double blind controlled study. This was simply a survey of rosacea sufferers who filled out a form and is purely anecdotal. The survey concluded the following according to an article in the JCAD:
"A 1999 survey by the National Rosacea Society of 3,151 rosacea patients determined different food triggers. With regard to alcohol ingestion in rosacea patients, this survey found red wine as the most likely culprit, followed by hard liquor, then beer as the least likely to cause symptoms in patients. With regard to spices, cayenne pepper aggravated rosacea 36 percent of the time, red pepper 34 percent of the time, black pepper 18 percent of the time, white pepper 9 percent of the time, and paprika 9 percent of the time." 
So whenever a physician or anyone says that spicy food is a rosacea trigger they are relying on evidence that is purely anecdotal. While the survey may prove helpful it is by no means a clinical study. Just because 36 percent of the respondents of the survey said they report cayenne pepper as a rosacea trigger doesn't mean that cayenne pepper is a rosacea trigger. All it means is that maybe it is a rosacea trigger since there is no clinical study to prove that indeed cayenne pepper is a rosacea trigger.
What a rosacea suffer needs to remember is that any proposed trigger is simply that, a proposed trigger. What triggers rosacea is an individual thing. Trigger avoidance is not an exact science and while it may prove helpful one must realize its limitations.
Every trigger proposed on the 1999 NRS survey is just a proposed trigger that MAY trigger rosacea. There has never been found one rosacea trigger that in every case produces a rosacea flare up. Not one.
Conclusion: Spicy food may be a rosacea trigger.
by Jonette E. Keri, MD, PhD, and Adena E. Rosenblatt
J Clin Aesthetic Derm. 2008;1(3):22–26