How Amphibians Breathe Through Their Skin Underwater

If you touch a frog’s skin, it feels slick and almost fragile. That texture does more than help it move through swampy ponds. It’s central to a way of breathing that doesn’t rely entirely on lungs. While humans have to use lungs for every breath, amphibians like frogs and salamanders can absorb oxygen and get rid of carbon dioxide through their skin, even when they’re completely underwater.

This works only because their skin is very thin and always kept moist by special mucous glands. The moisture is key; it dissolves oxygen from the air or water, letting it diffuse right into capillaries just below the surface. The exchange happens fast because the skin is just a few cell layers thick, with tiny blood vessels pressed close to the outside. Frogs can actually drown if their skin dries out, because then the oxygen exchange grinds to a halt.

Some salamanders in the family Plethodontidae go even further. These lungless salamanders have given up lungs completely, getting all their oxygen through their skin alone. To make this work, they’ve evolved long, slender bodies and delicate skin, combining more surface area with a short distance for oxygen to travel.

But this approach comes with limits. The surroundings need to stay cool and humid, or the animal won’t get enough oxygen and can suffocate. That explains why amphibians like damp, chilly spots. For them, the right environment is essential for catching each breath.

Frogs, newts, and other amphibians aren’t just tied to both land and water. Their thin skin is a living boundary, constantly managing the exchange between two worlds to keep them going.