Classification of patients complaining of sick house syndrome and/or multiple chemical sensitivity

Sick house syndrome (SHS) is a Japanese concept derived from sick building syndrome (SBS), however SHS includes a broader scope of sickness than does SBS. Symptoms of SHS/SBS disappear after leaving the sick house/building, while symptoms of multiple chemical sensitivity (MCS) are elicited by the chance of chemical exposure after leaving the sick house/building. To establish the concept of SHS, we propose to introduce a new classification for SHS. A total of 214 patients complaining of SHS and/or MCS were independently classified using a new classification by clinical ecologists who are experienced physicians with expert knowledge of clinical ecology and general physicians according to disease pathogenesis from clinical records. The classification is as follows: type 1 (symptoms of chemical intoxication), type 2 (symptoms developed possibly due to chemical exposure), type 3 (symptoms developed not because of chemical exposure but rather because of psychological or mental factors), and type 4 (symptoms developed due to allergies or other diseases). The agreements on the classification made by clinical ecologists and general physicians reached 77.1% (Cohen's kappa=0.631), suggesting that this new classification was both apt and accurate. Relations between SHS and allergy/MCS were also studied. The cases classified as SHS type 4 more frequently had allergic past histories than did other types. The proportion of possible MCS cases was higher in the chemical induced SHS group (types 1 and 2) than in other types among male patients. For the universal use in clinical practice, it is necessary to prepare helpful diagnostic criteria of this SHS classification based on pathogenesis and carry our study forward all over the country.