A new study suggests that topical nicotinamide "might be useful agents
for treatment of dermatological disorders such as acne vulgaris and rosacea."

The article involves the study of "rats treated intradermally with nicotinamide"
and concluded:

"This study provides direct in vivo evidence that nicotinamide and its
metabolite NMN(+) increase skin vascular permeability in rats by a
mechanism that may involve NO and prostaglandins."

An interesting part of the study says:

"Moreover, indomethacin, a cyclo-oxygenase 1 and 2 inhibitor and
N(G)-nitro-l-arginine methyl ester (l-NAME), a nitric oxide (NO) synthase
inhibitor, reduced the observed effects of nicotinamide and NMN(+)."

Wikipedia say that "Indometacin (INN) or indomethacin (USAN and former BAN)
is a non-steroidal anti-inflammatory drug commonly used to reduce fever, pain,
stiffness, and swelling. It works by inhibiting the production of
prostaglandins,
molecules known to cause these symptoms. It is marketed under many trade
names, including Indocin, Indocid, Indochron E-R, and Indocin-SR."

"A prostaglandin is any member of a group of lipid compounds that are derived
enzymatically from fatty acids and have important functions in the animal body.
Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring. They
are mediators and have a variety of strong physiological effects; although they
are technically hormones, they are rarely classified as such."

More on nicotinamide:

http://oscommerce.rosaceans.com/catalog/product_info.php?cPath=25&products_id=23\
9

Sources:

http://www.ncbi.nlm.nih.gov/pubmed/19175785?dopt=Abstract
http://en.wikipedia.org/wiki/Indomethacin
http://en.wikipedia.org/wiki/Prostaglandins