**Miliaria Disorder**

**Core Concept**
Miliaria, also known as prickly heat or heat rash, is a skin disorder caused by the blockage of sweat glands. This condition typically occurs in hot and humid environments, leading to the accumulation of sweat in the skin's eccrine glands.

**Why the Correct Answer is Right**
The correct answer is related to the eccrine glands, which are responsible for producing sweat in response to heat. When these glands become blocked, the sweat is unable to escape, causing the characteristic symptoms of miliaria. This condition is often seen in infants and young children, but can also occur in adults, particularly in hot and humid climates.

**Why Each Wrong Option is Incorrect**
* **Option A:** is incorrect because miliaria is not a disorder of the apocrine glands, which are a different type of sweat gland that is primarily responsible for producing sweat in response to emotional stimuli.
* **Option B:** is incorrect because miliaria is not a disorder of the sebaceous glands, which are responsible for producing sebum, an oily substance that helps to moisturize the skin.
* **Option C:** is incorrect because miliaria is not a disorder of the sweat glands in general, but rather a specific condition caused by the blockage of the eccrine glands.

**Clinical Pearl / High-Yield Fact**
Miliaria is often seen in infants and young children, but can also occur in adults, particularly in hot and humid climates. It is essential to identify and treat miliaria promptly to prevent further complications, such as skin infections.

**Correct Answer: D. Eccrine glands.**