Multiple Chemical Sensitivity (MCS) is a debilitating and complex condition that arises from exposure to certain chemicals found in everyday products. MCS is also referred to as Chemical Intolerance, Environmental Illness, or Chemical Sensitivity. Some people use the term Environmental Illness to describe MCS because it can affect the body's reaction to various environmental factors. Others use the term Toxicant-Induced Loss of Tolerance (TILT) to describe the condition. The common thread between all of these terms is that they describe a severe reaction to environmental toxins that can cause a range of symptoms, from headaches to respiratory problems to neurological issues. Whatever the term used, it is important to take MCS seriously and take steps to manage it if you are affected.