We hypothesize that the pathogenesis of rosacea may be influenced by exogenous stimuli (such as heat, spicy food, UV, physical, and microbes) and serine proteases (such as kallikrein 5 and kallikrein 14) that upregulate cathelicidin LL-37 through enhanced PAR2 signaling. The gene discussed is F2RL1; the disease is rosacea.