Normal variant of infant behavior: At 1 year of age, babies often exhibit behaviors like sticking their tongue out as part of their exploration and learning process. This could be a phase of development and might not indicate any underlying issue.

Teething or oral discomfort: The baby might be experiencing teething pain or oral discomfort, leading to the behavior of sticking their tongue out.
Neurodevelopmental variation: Some children with neurodevelopmental disorders or delays might exhibit repetitive behaviors, including sticking their tongue out, as part of their developmental profile.
Anxiety or stress: The child could be experiencing anxiety or stress, manifesting in this repetitive behavior.

Hypothyroidism: Although less common, hypothyroidism can cause macroglossia (enlarged tongue) which might lead to the child sticking their tongue out. Early diagnosis is crucial for treatment and preventing long-term effects.
Neurological conditions (e.g., cerebral palsy, dystonia): Certain neurological conditions can cause involuntary movements or postures, including tongue protrusion. Early identification is critical for appropriate management and intervention.

Tongue tie or oral motor issues: Although not the most common cause, a tongue tie or other oral motor issues could potentially lead to this behavior as the child tries to compensate for difficulties in moving their tongue.
Genetic syndromes (e.g., Down syndrome, Beckwith-Wiedemann syndrome): Some genetic syndromes are associated with macroglossia or other oral and facial abnormalities that could result in the child sticking their tongue out.
Infections or autoimmune conditions affecting the brain or oral cavity: Rare infections or autoimmune conditions could potentially cause this behavior, although these would be less likely and might be accompanied by other significant symptoms.