Demodex refers to a genus of tiny mites that live on the skin of mammals, including humans. These microscopic creatures are usually harmless and are part of the normal skin flora. There are two main species that affect humans: Demodex folliculorum and Demodex brevis, which primarily inhabit hair follicles and sebaceous glands. While most people carry these mites without any issues, an overpopulation can lead to skin problems, such as rosacea or other inflammatory conditions. Factors like a weakened immune system or hormonal changes can contribute to their increase, highlighting the importance of maintaining skin health.