Which type of gland secretes a milky protein that acts as a nutrient medium for skin microorganisms?

Apocrine glands are responsible for secreting a milky protein-rich substance that serves as a nutrient medium for skin microorganisms. These glands are primarily located in areas such as the armpits and groin and become active during puberty. The secretion from apocrine glands contains proteins and lipids that bacteria on the skin can break down, potentially leading to body odor.

In contrast, eccrine glands primarily secrete a watery fluid that helps in thermoregulation through sweating. Feromone glands, while involved in chemical signaling, do not directly produce the substance described in the question. Dermal glands is a more general term and does not specifically refer to the type of secretion or function related to the question posed. Thus, understanding the unique role of apocrine glands clarifies why they are the correct answer.