Atopic Dermatitis (Eczema): This is a common condition in infants and toddlers, characterized by itchy, inflamed skin. The perioral area is a typical location, and the age of the child fits with the usual presentation of atopic dermatitis.

Irritant Contact Dermatitis: This could be due to exposure to irritants like saliva, food, or other substances that come into contact with the skin around the mouth. It's common in children who drool or have poor oral hygiene.
Allergic Contact Dermatitis: An allergic reaction to something that has come into contact with the skin, such as a new toothpaste, food, or a component of a pacifier.
Impetigo: A contagious bacterial skin infection that can cause red sores or blisters, often around the mouth. It's itchy and can be accompanied by a honey-colored crust.

Herpes Simplex Virus (HSV) Infection: Although less common, HSV can cause perioral lesions that are painful and itchy. It's crucial to distinguish this from other causes due to its potential for serious complications if not treated.
Scabies: Caused by a mite, scabies can lead to severe itching and a pustular rash. It's highly contagious and can affect any part of the body, including the face.

Kawasaki Disease: A rare condition that mainly affects children under the age of 5. It can cause a rash, fever, and swelling, among other symptoms. Although it's rare, it's a critical diagnosis to consider due to its potential for cardiac complications.
Acrodermatitis Enteropathica: A rare genetic disorder affecting zinc absorption, leading to skin lesions, diarrhea, and other symptoms. The skin lesions can be similar to those seen in eczema or other dermatitis forms but are typically more severe and resistant to treatment.