In seborrheic dermatitis, which site is the most commonly affected?

Seborrheic dermatitis is primarily characterized by inflamed, flaky skin and is most commonly seen in areas rich in sebaceous (oil) glands. The scalp is particularly affected because it is one of the regions with a high concentration of these oil-producing glands.

In seborrheic dermatitis, the presence of Malassezia yeast, a normal skin inhabitant that can become overgrown in certain conditions, also plays a significant role. This yeast thrives in sebaceous areas, leading to skin irritation and inflammation typically found on the scalp in the form of dandruff and flaky patches.

While seborrheic dermatitis can also affect other areas such as the face (especially around the nose and eyebrows), chest, and back, the scalp remains the most classic and well-documented site. The other options, such as the upper extremities, thighs, and feet, are not typical sites for seborrheic dermatitis, as they have a lower density of sebaceous glands and are less prone to the proliferation of the Malassezia fungi that contribute to this condition. Hence, the scalp is recognized as the most commonly affected area in seborrheic dermatitis.