**Core Concept**
Atopic dermatitis, also known as eczema, is a chronic inflammatory skin condition characterized by dry, itchy, and scaly skin. It is a complex disease involving an interplay of genetic, environmental, and immune system factors. The pathophysiology of atopic dermatitis involves a dysregulated immune response, leading to increased levels of Th2 cytokines and the release of histamine from mast cells.

**Why the Correct Answer is Right**
The correct answer is the skin barrier, specifically the stratum corneum. The skin barrier plays a crucial role in preventing water loss and protecting against external pathogens. In atopic dermatitis, the skin barrier is compromised due to mutations in the filaggrin gene, leading to impaired keratinization and increased permeability. This allows allergens and irritants to penetrate the skin, triggering an immune response and inflammation.

**Why Each Wrong Option is Incorrect**
* **Option A:** The sweat glands are not directly involved in the pathogenesis of atopic dermatitis.
* **Option B:** The sebaceous glands are not the primary site of inflammation in atopic dermatitis.
* **Option C:** The lymph nodes are involved in the immune response, but they are not the primary site of atopic dermatitis.

**Clinical Pearl / High-Yield Fact**
Atopic dermatitis is associated with an increased risk of developing other atopic diseases, including asthma and allergic rhinitis. Patients with atopic dermatitis are more likely to have a family history of these conditions, highlighting the importance of a comprehensive medical and family history in diagnosis and management.

**Correct Answer: C. Lymph nodes are not the MC site of Atopic dermatitis.