The mean ± SD serum prolactin levels of the chronic migraineurs (1.82 ± 0.94) and those with ictal EM (1.93 ± 1.70) were comparable and were significantly higher than for interictal EM patients (0.82 ± 0.46) and the headache‐free control subjects (0.49 ± 0.15; p < .001). The gene discussed is PRL; the disease is erythema multiforme.