What is the primary characteristic of seborrheic dermatitis?

The primary characteristic of seborrheic dermatitis is indeed the presence of red skin with white scales. This skin condition commonly affects oily areas of the body such as the scalp, face, and back, leading to inflammation and the formation of flaky, scaly patches that can appear on the skin. The scales are often yellowish-white or whitish in color and can adhere to the skin, sometimes resembling dandruff.

This condition is more commonly seen in individuals with oily skin or those with conditions such as psoriasis or eczema. While the appearance can be associated with discomfort, the hallmark is significantly the red coloration and the characteristic scales, differentiating it from other conditions such as eczema or fungal infections.

The other options present features that do not accurately describe seborrheic dermatitis. Flaky skin on its own does not convey the inflammation or redness associated with this condition. Red and painful blisters are indicative of a different type of skin problem, potentially an allergic reaction or infection. Severe itching may occur with seborrheic dermatitis, but it is not the defining characteristic, as the scales and redness tend to take precedence in diagnosis and observation.