BACKGROUNDHomeopaths report that individuals with heightened self-reported environmental chemical intolerance (CI) exhibit increased reactivity to homeopathic remedies. Persons high in CI sensitize their electroencephalographic (EEG) alpha responses to repeated intermittent chemical exposures.PRIMARY STUDY OBJECTIVEThe present feasibility study explored interactions between CI and one of two specific homeopathic remedies over time (Sulphur or Pulsatilla nigricans [Pulsatilla]).DESIGNThis study used a two-arm, double-blind, placebo-controlled repeated measures design. Intervention Participants underwent a series of three once-weekly sessions during which they repeatedly sniffed one remedy (6c, 12c, 30c; one potency per week) matched to their Homeopathic Constitutional Type Questionnaire (CTQ) type and two solvent controls (distilled water and a waterethanol [95%] solution). Within sessions, remedies and control solvents were administered via 2-second sniffs (eight sniffs of each of four different succussion levels per potency, in randomized order).PARTICIPANTSParticipants were college student volunteers (N = 96, ages 18-30, both sexes), screened for good health and relatively elevated Sulphur or Pulsatilla symptom pattern scores on the Homeopathic Constitutional Type Questionnaire (CTQ). Participants also completed a validated trait CI scale.PRIMARY OUTCOME MEASURESAverage 19-lead relative EEG alpha power (alpha 1 8-10 Hz; alpha 2 10-12 Hz).RESULTSTrait CI interacted significantly with time factors for each remedy (both over visit weeks and over sniff cycles during sessions). The patterns were nonlinear and differed between the two remedies. Individuals high in CI showed greater variability over time in remedy EEG alpha effects than did those low in CI.CONCLUSIONThe data suggest that CI, with an underlying susceptibility to time-dependent sensitization and oscillatory responses, could contribute to nonlinear dose-response patterns and inconsistent reproducibility of homeopathic clinical care and research.