Food Allergy: This is the most likely diagnosis, given the temporal relationship between eating chicken and rice and the development of a maculopapular rash. A common allergen in chicken or a component of the meal could trigger an allergic reaction, manifesting as a skin rash.

Irritant Contact Dermatitis: If the chicken and rice were not properly handled or were contaminated, irritants could cause a contact dermatitis, leading to a maculopapular rash.
Gastroenteritis with Rash: Certain gastrointestinal infections can cause a rash, and if the chicken and rice were contaminated with a pathogen, this could be a possible diagnosis.
Drug Reaction: If the patient recently started a new medication, a drug reaction could manifest as a maculopapular rash, potentially triggered or exacerbated by the meal.

Anaphylaxis: Although anaphylaxis typically presents with more severe symptoms such as difficulty breathing, rapid heartbeat, and a drop in blood pressure, a maculopapular rash can be an early sign. It's crucial to consider anaphylaxis due to its potential for severe outcomes if not promptly treated.
Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN): These are severe skin conditions usually triggered by medications or infections. They can start with a maculopapular rash and progress to blistering and peeling of the skin, which can be life-threatening if not recognized and treated early.

Eosinophilic Gastroenteritis: A rare condition characterized by eosinophilic infiltration of the gastrointestinal tract, which can cause a variety of symptoms including rash, especially after eating specific foods.
DRESS Syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms): A rare but serious condition that can be triggered by medications or, less commonly, by infections or foods. It presents with a rash, fever, and internal organ involvement, and can be life-threatening if not recognized and treated appropriately.