Host-microbe interactions: Malassezia and human skin.

The skin is our first line of defense, protecting us from invasion and evaporation. Its variable structure, changing geography, and complex immune repertoire provide a vast interface for our cutaneous microbial community. Skin is inhabited by many thousands of microbes, but this review focuses on the dominant eukaryote, Malassezia, and its host interaction. Malassezia compromises 17 species with variable niche specificities and differing pathogenic potential. It has been known as a skin inhabitant for over 100 years, and is now accepted to be on all warm-blooded animals. Malassezia occupy healthy and diseased skin, so their role as commensal or pathogenic organisms is complex. Malassezia interact with their host indirectly through immune interplay and directly via chemical mediators. While some interactions are known, many remain to be fully understood.