Atopic Dermatitis (Eczema): This is the most likely diagnosis due to the pruritic nature of the rash and its location on the face, neck, and bilateral axilla, which are common areas affected by atopic dermatitis. The condition is characterized by chronic inflammation and is often associated with allergies and asthma.

Contact Dermatitis: This could be either irritant or allergic contact dermatitis, caused by exposure to substances that irritate the skin or trigger an allergic reaction. The locations mentioned could be prone to such exposures.
Seborrheic Dermatitis: Although it more commonly affects the scalp, face, and torso, seborrheic dermatitis can cause a pruritic rash and might involve the neck and axillary regions, especially in severe cases.
Pityriasis Rosea: While it typically starts with a herald patch followed by a wider rash on the trunk, pityriasis rosea can sometimes involve the face and neck, and it is known for its pruritic nature.

Bullous Pemphigoid: An autoimmune disease that can cause very pruritic blisters, which might initially appear as a rash. It's crucial to diagnose early due to potential complications.
Dermatitis Herpetiformis: Characterized by extremely itchy blisters, this condition is associated with celiac disease and requires a strict gluten-free diet for management.
Cutaneous T-Cell Lymphoma (Mycosis Fungoides): A rare form of skin cancer that can present with patches, plaques, or tumors and is often very pruritic. Early diagnosis is critical for effective treatment.

Grover's Disease: A rare skin condition that causes small, itchy bumps or blisters, often on the trunk, but can appear elsewhere, including the face and neck.
Erythema Dyschromicum Perstans: A rare condition characterized by the gradual appearance of hyperpigmented patches, often with a burning or pruritic sensation, more commonly seen in Latin American populations.