Oral Thrush (Candidiasis): This is the most common cause of white spots in the mouth of infants and young children. The red border around the spots is consistent with an inflammatory response to the fungal infection. Oral thrush is easily treatable with antifungal medications.

Traumatic Ulcers: These can appear as white or yellowish spots with a red border due to inflammation. They are common in infants who may accidentally bite their cheek or tongue.
Herpes Simplex Virus (HSV) Infection: Although less common, HSV can cause oral lesions that might appear as white spots with a red border, especially during the initial stages of infection.
Hand, Foot, and Mouth Disease (HFMD): Caused by viruses like Coxsackievirus, HFMD can lead to oral lesions, including white spots with red borders, though these are typically accompanied by lesions on the hands and feet.

Leukemia or Lymphoma: Though rare, these conditions can cause oral lesions, including white spots. It's crucial to consider these diagnoses to ensure timely treatment if present.
Immunodeficiency: Conditions that impair the immune system, such as HIV/AIDS, can predispose children to opportunistic infections like oral thrush, but the presence of recurrent or severe infections may indicate an underlying immunodeficiency.
Stevens-Johnson Syndrome: A severe skin and mucous membrane disorder, usually a reaction to medication or infection, which can cause oral lesions among other symptoms.

Lichen Planus: An autoimmune condition that can affect the mucous membranes inside the mouth, leading to white, lacy patches or red, inflamed tissues.
Pemphigus: A group of rare skin disorders that cause blistering of the skin and mucous membranes, which can include the oral mucosa.
Oral Mucositis: Often associated with chemotherapy or radiation therapy, this condition can cause mouth sores and white spots, but it's less likely in a 1-year-old without a history of such treatments.