What causes a thick tongue? An enlarged or swollen tongue can also occur as an allergic reaction to medications or other substances. In this case, the swelling is due to fluid accumulation in the tissues of the tongue, medically known as angioedema. A dramatically swollen tongue can lead to breathing problems and may be a medical emergency. How thick should tongue be? The general rule says you should have a square tongue that's roughly one-third of the stock thickness and centered on the edge. Working with 3⁄4″ stock, that plays out to a 1⁄4″-thick by 1⁄4″-long tongue, and a matching groove.