Which of the following is a natural antibiotic found in skin?

Human defensin is a naturally occurring antibiotic found in the skin that plays a crucial role in the innate immune system. These small peptides have antimicrobial properties and are produced by various cells in the body, including those in the skin. They function by disrupting the membranes of bacteria, fungi, and some viruses, thereby neutralizing potential threats and preventing infections. This defensive mechanism is particularly important as the skin serves as the first line of defense against pathogens.

On the other hand, ceramides, collagen, and keratin are essential components of the skin but do not have antibiotic properties. Ceramides are lipids that help maintain skin barrier integrity and hydration. Collagen provides structural support and contributes to skin elasticity and strength, while keratin is a fibrous protein that makes up the outermost layers of skin and hair, offering protection but not direct antimicrobial activity. Thus, while all these substances contribute to overall skin health and protection, only human defensin functions specifically as a natural antibiotic.