The following websites provide three overviews of multiple chemical sensitivity (MCS). The first is written by Dr Ann McCampbell, a leading advocate for those with MCS and author of numerous articles on MCS.
The second overview is written by the Chemical Injury Information Network (CIIN), a support and advocacy organization dealing with MCS.
The third link is to the official definition of multiple chemical sensitivity. This consensus of 89 medical professionals and researchers with extensive experience with MCS was written in 1999 and it remains the official definition of MCS.
Dr Ann McCampbell’s Multiple Chemical Sensitivity http://annmccampbell.com/multiple-chemical-sensitivity/
CIIN’s An Overview of MCS http://ciin.org/mcs.html
Multiple Chemical Sensitivity: A 1999 Consensus https://www.ei-resource.org/articles/multiple-chemical-sensitivity-articles/multiple-chemical-sensitivity-a-1999-consensus/