Subantimicrobial doxycycline is an anti-inflammatory drug that decreases cathelicidin, kallikrein 5, reactive oxygen species, nitric oxide, and matrix metalloproteinases. Clinical trials demonstrated a comparable efficacy to 100-mg doxycycline in papulopustular rosacea with improvement of inflammatory lesions, quality of life, and improved safety profile. Case series and case reports suggested efficacy in other inflammatory skin diseases. The response of papulopustular rash during targeted anticancer therapies is mixed. Further studies are needed.