The potential role in rosacea of white blood cells, known as neutrophils, and the substances they produce was described in a presentation at the American Academy of Dermatology annual meeting in Orlando. Dr. David E. Cohen, professor of dermatology at the NYU School of Medicine, noted that the skin of rosacea patients is often filled with neutrophils. 

“Not only do [the neutrophils] participate in the inflammation, but they dump out highly noxious substances into the dermis, because that’s their function,” Dr. Cohen explained. They secrete nitric oxide, which causes vasodilation, as well as reactive oxygen species, matrix metalloproteinases (MMPs) and cathelicidins. “This all contributes to the ongoing inflammation, but the neutrophils are basically doing what they’re told to do. They’re not abnormal neutrophils, they’re abnormally infiltrating into rosacea [skin].” 

Reactive oxygen species are chemically reactive molecules containing oxygen, such as hydrogen peroxide. They are naturally produced by neutrophils to kill foreign organisms, but because they are naturally toxic, they cause inflammation in the body as well. MMPs are enzymes that break down different types of skin tissue, such as collagen, gelatin and elastin, as part of the wound healing process. Dr. Cohen explained that when these substances are present in the skin for an extended period of time, they slowly destroy the normal structure of the skin and cause chronic inflammation. 

Cathelicidins are part of the innate immune system and act to protect the body by producing antimicrobial agents. MMPs have the ability to produce enzymes that activate cathelicidins, which in turn attract more neutrophils.