Rosacea is an inflammatory skin disease characterised by abnormal redness of the skin, spider veins and small bumps on the skin surface, normally affecting those above the age of 30. It is thought to affect approximately 3 percent of the population above 30, meaning that in the US alone there are likely to be at least 9 million sufferers. Although much is known about factors that may aggravate the condition, little has been known about the pathogenesis of the condition. However, a study published in this months Nature Medicine, suggests a possible mechanism that may lead to the condition, that the researchers say 'may modify the therapeutic approach to treating rosacea.' The team led by Richard L Gallo included researchers from the University of California, the Asahikawa Medical College in Japan, and researchers from Toulouse, France. The team found that individuals suffering from rosacea appeared to have abnormally high levels of cathelicidin, a protein released as part of a normal immune response. In addition these cathelicidins appear to be different in rosacea patients; when broken down by protease (enzymes targeted to break down cellular proteins) they degrade into substances different to those in normal individuals. These abnormal cathelicidins are thought to be the result of a processing abnormality associated with an increase in stratum corneum tryptic enzyme (SCTE) found in the epidermis. The team tested the hypothesis that increased protease activity and abnormal cathelicidins leads to rosacea by injecting the peptides and the SCTE into laboratory mice, whilst increasing the protease activity by deletion of a protease inhibiting gene. The mice developed skin inflammation, thereby lending support to the team's hypothesis. Traditionally rosacea has been treated with antibiotics which, although not particularly effective, can alleviate certain symptoms, as they work to inhibit some of the enzymes involved. However, this research suggests that a new therapeutic approach might be beneficial as bacteria are not the right target; in addition increased knowledge of the etiology of the disease will significantly aid the discovery of possible treatments, including a variety of topical alternatives.