Cause of tongue pretrusion in. a toddler?

Breathing obstructio: Breathing may be difficult due to swelling in throat. I suggest a visit to a doctor asap.

Need more info: If this is acute take toddler to doctor asap. A condition known as acute epiglottitis can produce tongue protrusion, but usually accompanied by fever and shortness of air. If this is a chronic problem may be other things (enlarged tonsils, etc.). Either way you should see a pediatrician, but timing depends on severity and other factors.