Halothane sensitivity describes swine that react to halothane inhalation with malignant hyperthermia, and such animals also show enhanced sensitivity to everyday stress. Pork from these stress-susceptible pigs is likely to develop the pale, soft, exudative (PSE) defect, becoming watery and unappealing after the rapid post-mortem pH fall that stress triggers. Halothane sensitivity is one of the classic genetic disorders of pigs; the halothane or porcine stress syndrome genotype may be nn (homozygous susceptible), Nn (carrier) or NN (normal). DNA testing has largely replaced the anaesthetic challenge, letting breeders eliminate the defective gene and dramatically reduce PSE meat.