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    Parasites and inflammation fuel rosacea


    Two types of demodex

    There are two types of demodex in humans, and some investigations have sought to quantify the colonization of demodex folliculorum, which lives in sebaceous follicles, in patients with rosacea and how colonization is related to immune activation of the skin. Not only did skin sample analysis demonstrate that density of demodex folliculorum was 5.7 times greater in rosacea patients compared to control subjects, but there was a higher expression of genes carrying pro-inflammatory cytokines in rosacea, particularly in papulopustular rosacea compared to erythematotelangiectatic rosacea.2

    Still, demodex density is increased in rosacea patients, independent of the rosacea subtype.

    "There are patients with erythematotelangiectatic rosacea who have higher levels of demodex on the face and patients with papulopustular rosacea who have less (demodex on the face)," Dr. Gooderham says.


    Recommended: Microbial considerations in rosacea treatment

    Genes matter

    Certain individuals are more genetically predisposed to develop rosacea. A recent analysis of twins aimed to separate environmental factors from genetic susceptibility in terms of the contribution to rosacea. Investigators concluded roughly half of the contribution to the rosacea score, as determined by the National Rosacea Society, is owing to genetics.3

    Some investigators have speculated that a dysregulated immune response likely makes individuals more at risk of reacting to environmental stimuli like ultraviolet exposure and hot beverages.

    Read: Rosacea's surprising genetic link

    An emerging tool to measure the density of demodex mites in patients with rosacea is reflectance confocal microscopy. The technology can be used to detect and measure the mites in vivo in a non-invasive manner before and after treatment to measure any change in density. A decrease in density would be suggestive of clinical improvement.4

    Greater understanding of the pathogenesis of rosacea may offer an explanation with respect to the efficacy of newer therapies such as ivermectin 1% cream, Dr. Gooderham says.

    "Ivermectin is anti-parasitic and it has anti-inflammatory properties as well," says Dr. Gooderham. "It works at the level of cathelicidins. This may be why ivermectin is working (to treat rosacea)."

    Research from two randomized, double-blind, controlled studies point to the effectiveness and safety of ivermectin in reducing inflammatory lesions when pitted against vehicle.5

    In addition, the therapy has been shown to be safe and effective in extension studies, supporting its use as a long-term treatment.6


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