Atopic Dermatitis (Eczema): This is a common condition in children, characterized by itchy, inflamed skin. The perioral area can be involved, and the age of the patient fits within the typical range for atopic dermatitis onset.

Irritant Contact Dermatitis: This condition occurs when the skin comes into contact with an irritant, such as soap, food, or other substances that can cause a reaction around the mouth.
Allergic Contact Dermatitis: Similar to irritant contact dermatitis but involves an allergic reaction to substances like metals, fragrances, or certain foods.
Seborrheic Dermatitis: Although more common in infants and adults, seborrheic dermatitis can occur in toddlers and may present with a perioral distribution.
Perioral Dermatitis: The condition itself, more common in adults but can occur in children, especially with the use of topical steroids or other irritants.

Impetigo: A highly contagious bacterial infection that can present with redness and lesions around the mouth. It's crucial to diagnose and treat to prevent spread.
Herpes Simplex Virus (HSV) Infection: Can cause oral and perioral lesions, and while less common in this specific presentation, it's critical to identify due to the potential for serious complications.
Lip Licker's Dermatitis: Though not typically dangerous, it's a condition that can mimic perioral dermatitis and is caused by chronic licking of the lips, leading to irritation and dermatitis.

Gianotti-Crosti Syndrome: A rare condition characterized by a rash, including perioral lesions, often associated with viral infections.
Acrodermatitis Enteropathica: A rare genetic disorder affecting zinc absorption, which can lead to skin lesions, including around the mouth.
Histoplasmosis or Other Fungal Infections: Though rare, fungal infections can cause skin lesions and should be considered, especially in immunocompromised children or those exposed to certain environments.