KLK5 and rosacea: Subantimicrobial dosages are preferred to prevent changes to gut microbiota and reduce risk of gastrointestinal adverse reactions and development of resistance.6 The efficacy of doxycycline in treating rosacea is likely due to its ability to downregulate several factors involved in rosacea pathogenesis including interleukin 1β, tumour necrosis factor α (TNFα), kallikrein-5 (KLK5), cathelicidin, and matrix metalloprotease 9.58,59