Atopic Dermatitis (Eczema): This is the most common chronic skin condition in children, characterized by itchy, inflamed skin that can present with papules and pustules. The age of the patient and the description of the rash make this a highly probable diagnosis.

Impetigo: A contagious skin infection that can cause itchy, red sores or blisters that can burst and form light brown crusts. It's common in children and can present with pustules.
Scabies: Caused by a mite, this condition leads to intense itching, especially at night, and a pustular rash. It's highly contagious and common in children.
Keratosis Pilaris: A harmless condition that causes small, rough, sandpaper-like bumps on the skin, often on the arms, legs, buttocks, and cheeks. It can sometimes be itchy.

Staphylococcal Scalded Skin Syndrome (SSSS): Although rare, SSSS is a serious condition caused by staphylococcal toxins that can lead to widespread skin lesions and can be life-threatening. It's crucial to consider this in any child with a severe skin condition.
Allergic Contact Dermatitis: While not typically life-threatening, severe cases can significantly impact quality of life. It's essential to identify and remove the allergen causing the reaction.

Pityriasis Lichenoides: A rare skin condition characterized by small, raised bumps that can resemble papules or pustules. It's usually self-limiting but can be itchy.
Papular Urticaria: An allergic reaction to insect bites, characterized by itchy papules. It's less common but should be considered, especially if the child has been exposed to insects.
Bullous Pemphigoid: A rare autoimmune disease that can cause large blisters and is very rare in children. However, it's essential to consider in cases of severe or unexplained skin conditions.