Atopic Dermatitis (Eczema): This is a common condition characterized by itchy, inflamed skin. The back of the neck is a typical location for atopic dermatitis, especially in individuals with a history of allergies or asthma. The pruritic nature of the rash and its location make atopic dermatitis a leading consideration.

Contact Dermatitis: This condition occurs when the skin comes into contact with an allergen or irritant, leading to a pruritic rash. The back of the neck can be exposed to various substances (e.g., hair dyes, fragrances, metals) that could trigger an allergic or irritant reaction.
Seborrheic Dermatitis: Although more commonly associated with the scalp, face, and ears, seborrheic dermatitis can occasionally present on the back of the neck, causing a pruritic, erythematous rash.
Psoriasis: While psoriasis can occur anywhere on the body, it often affects the scalp, elbows, and knees. However, it can also appear on the back of the neck, presenting as a pruritic, scaly plaque.

Meningitis: Although extremely rare and unlikely to present solely as a pruritic rash on the back of the neck, meningitis can have a rash (e.g., in the case of meningococcal infection). It's crucial to consider this diagnosis due to its high mortality rate if left untreated.
Lymphoma: Cutaneous T-cell lymphoma (e.g., mycosis fungoides) can present with skin lesions that are pruritic and can appear on the back of the neck. Given the potential severity of lymphoma, it's essential to keep this diagnosis in mind.

Dermatomyositis: An autoimmune condition characterized by skin rash and muscle weakness. The rash can be pruritic and may appear on the back of the neck, although it more commonly affects the face, arms, and legs.
Pityriasis Rubra Pilaris: A rare skin disorder that can cause a pruritic rash, often starting on the face or upper body, including the back of the neck. It's characterized by small, pointed bumps and orange-red scaling patches.