It's hard to pinpoint the exact origins of MCS. I thought it was Lyme but I definitely had experiences before that. As a young child, my mom bought a new car and the smell of it made me incredibly sick. She did not believe me and would not listen. Every car ride made me feel sick with headache and nausea. It ruined my days at school after commuting in that car. Slowly I realized that other smells would affect me as well. When Lyme hit me in 2014, it completely exacerbated the MCS and now there is barely a manmade smell I can tolerate. I also react poorly to some herbs like Lavender, which is a shame because I am a professional gardener. Basically it's very hard to explain to others and many people are not sympathetic, or even purposely expose me to smells to mess with me.