Why are lips numb after eating puffer fish?

Lips may become numb after eating puffer fish due to the presence of tetrodotoxin, a potent neurotoxin found in some species of puffer fish. This toxin can block sodium channels in nerve cells, leading to paralysis and loss of sensation, particularly in the mouth and lips. If consumed improperly prepared, puffer fish can cause serious poisoning, which is why it is considered a delicacy only in certain cultures, where trained chefs prepare it safely.