 Glands in the skin discharge mucus which keeps the skin moist , an important factor in skin respiration and thermoregulation . The sticky layer helps protect against bacterial infections and molds , reduces friction when swimming , and makes the animal slippery and more difficult for predators to catch . Granular glands scattered on the upper surface , particularly the head , back , and tail , produce repellent or toxic secretions . Some salamander toxins are particularly potent . The rough @-@ skinned newt ( Taricha granulosa ) produces the neurotoxin tetrodotoxin , the most toxic nonprotein substance known . Handling the newts does no harm , but ingestion of even a minute fragment of skin is deadly . In feeding trials , fish , frogs , reptiles , birds , and mammals were all found to be susceptible . 
