"...There is no specific test for rosacea, but its characteristic appearance, cutaneous distribution, discrete course, typical target population, and response to various therapies make accurate diagnosis possible....
...It is estimated that rosacea occurs in about 13 million (1 in 20) Americans. Onset occurs between 30 and 50 years of age in about half of patients.
Rosacea appears to occur most often in fair-skinned people of northern and eastern European descent, particularly Celtic, English, and Scottish. It often affects multiple members of the same family, presumably because of their similar complexions and genetic heritage...." - --- source of article > http://www.postgradmed.com/issues/1999/02_99/millikan.htm
"There are no histological, serological or other diagnostic tests for rosacea. A diagnosis of rosacea must come from your physician after a thorough examination of your signs and symptoms and a medical history." - NRS, Answer to Question 5, source
However, according to UCSD, "A diagnostic test for rosacea can be developed by identifying higher levels of these specific peptides, or the processed forms, in patients suspected of having rosacea, distinguishing it from other dermatological or autoimmune diseases." source
