Please note: In my book, Rosacea 101, (published in October 2007) in Chapter 1, What is Rosacea?, page 1, and Chapter 2, Rosacea Mimics, page 9, you can read an updated version of what I wrote below which was used as part of the basis of both chapters. Acne has been confused with rosacea while at the same time you can have acne along with your rosacea! My new book is a comprehensive basic rosacea 101 knowledge for rosacea newbies who want to learn about the conventional and alternative treatments for rosacea.

Rosacea has been called 'adult acne' often. Sometimes rosacea is called 'acne rosacea.' However, technically acne is distinct from rosacea. While you may have acne and rosacea at the same time there is a distinct difference between the two. Acne is technically a condition while rosacea is a disease. Acne vulgaris is a disease different from rosacea.

Acne can be concurrent with rosacea in some cases and adds to the confusion. The problem is that sometimes using treatments for acne can aggravate rosacea (read the list of possible topicals that aggravate rosacea). However, there is one theory that acne and rosacea have a common cause:

Based on the theory that rosacea shares the same inflammatory features of acne, a recent study showed that, just as the combination of benzoyl peroxide 1 percent and clindamycin 5 percent gel is a powerful treatment modality for reducing Propionibacterium acnes levels, it also significantly reduces the papules and pustules of rosacea, according to Debra L. Breneman, M.D. ...."Benzaclin, once daily, was found to be well tolerated and effective in the reduction of papules and pustules in patients with rosacea," said Dr. Breneman. "This lends credence to the theory that P. acnes is a potential aggravating factor in rosacea. This gives dermatologists a very effective treatment for rosacea." Source >http://www.dermatologytimes.com

It should be noted that no one knows for sure what is causing rosacea. [source] The International Rosacea Foundation has this to say about the acne rosacea:

"...Note: Pustules are NOT pimples. Pimples have a bacterial component to their makeup and are also mainly localized in and around the hair follicles....

...As the condition [rosacea] progresses, flushing becomes more persistent and noticeable. Small, red, solid bumps (called papules) and pus-filled pimples (called pustules) may appear on the skin. Because these appear similar to acne, rosacea is sometimes called acne rosacea or adult acne. However, unlike acne, there are no blackheads. Though rosacea is sometimes referred to as "adult acne," it is a distinctly different and often more serious condition than acne vulgaris, which most commonly occurs during adolescence. While both conditions can cause pimples, rosacea requires different therapy -- acne treatments can actually make it worse -- and rosacea rarely goes away by itself....

...The following other conditions can have symptoms similar to rosacea:

According to the American Academy of Dermatology, Acne is the term for plugged pores (blackheads and whiteheads), pimples, and even deeper lumps (cysts or nodules) that occur on the face, neck, chest, back, shoulders and even the upper arms. Acne affects most teenagers to some extent, but can also affect adults in their 20s, 30s and 40s. While there is no permanent cure for acne, it is controllable...." source >

http://internationalrosaceafoundation.org/

Some topicals that are used for acne may aggravate rosacea and a list of these possible aggravating factors may be read by my book in Chapter 11, page 45, Triggers.