卡英酸（英语：kainic acid），又称红藻酸、红藻胺酸、海人酸，是一种类似麸胺酸（glutamic acid）的化合物，为神经传递很强的药物，萃取自海底的藻类。

卡英酸最早由日本发现应用在孩童驱虫药，并且销往东亚各国，早期**也是仰赖进口，甚至在公元1971年**景德制药厂兴建厂房大量生产海人酸，但在日本临床上发现服用卡英酸治疗寄生虫的幼童都纷纷有癫痫的症状，因此这个药物马上遭禁用。也因为这个医疗上的发现，使卡英酸发展成不同的应用方式，目前卡英酸应用在诱发癫痫。

Kainic acid (kainate) is a natural marine acid present in some seaweed. Kainic acid is a potent neuroexcitatory amino acid that acts by activating receptors for glutamate, the principal excitatory neurotransmitter in the central nervous system. Glutamate is produced by the cell’s metabolic processes and there are four major classifications of glutamate receptors: NMDA receptors, AMPA receptors, kainate receptors, and the metabotropic glutamate receptors. Kainic acid is an agonist for kainate receptors, a type of ionotropic glutamate receptor. Kainate receptors likely control a sodium channel that produces excitatory postsynaptic potentials (EPSPs) when glutamate binds.