Treating Multiple Chemical Sensitivity as a Specific Phobia Using Cognitive Behavioural Therapy: A Case Study in an Older Adult

Multiple Chemical Sensitivity (MCS) is a poorly understood condition characterised by physical symptoms triggered by minimal exposure to odorous or chemical agents, often without identifiable organic pathology. This case study describes cognitive behavioural therapy (CBT) for MCS in an older adult referred to a respiratory team after developing persistent, generalised reactions to odours following an acute toxic inhalation. Symptoms led to severe avoidance, functional impairment and suicidal ideation. Following medical evaluation, psychological assessment did not support the alternative diagnoses considered and informed a working formulation of specific phobia. Treatment comprised 14 sessions, beginning virtually because of avoidance, progressing to in vivo exposure and concluding with relapse-prevention planning. Outcome measures and self-report indicated substantial reductions in anxiety and health-related worry, alongside achievement of all functional goals. Improvements were maintained at 10- and 22-month follow-up, with low anxiety scores and marked reductions in beliefs about harm from previously feared stimuli. This case illustrates how a specific-phobia formulation and phobia-focussed CBT may be applicable to some MCS presentations following appropriate medical evaluation. It also highlights a potential role for clinical psychologists in respiratory settings. As a single case, the findings provide descriptive evidence of improvement but cannot establish a causal treatment effect.