Everyone knows and hates the viruses that cause nausea and headaches. But have you ever thought to fear the desks and walls of your own office or home? Today, buildings themselves seem to be a serious health issue.

Dr. Lynn Marshall, of the Environmental Health Clinic at the Women’s College Hospital, recently gave a presentation on environment-linked conditions that have become increasingly common during the last few decades-“invisible illnesses” whose symptoms often go unseen. She focused on four main chronic conditions: “sick building syndrome,” chronic fatigue syndrome, fibromyalgia, and multiple chemical sensitivity.

These four conditions, which mostly affect middle-aged women, are linked to poor ventilation and exposure to certain chemicals in the environment where people live and work. Common culprits include dustmites, moles that thrive in damp areas, pet dander, pollen, inorganic chemicals (nitrogen dioxide and sulfur dioxide gases), volatile organic compounds like paint thinner and persistent organic pollutants like dioxins.

According to Marshall, the four invisible conditions are closely linked and even have similar symptoms-so similar that sometimes a physician is unable to pinpoint the patient’s problem. For instance, the symptoms of sick building syndrome include (but are not limited to) dizziness, headaches, nausea, dry coughs, insomnia, and difficulty concentrating, all of which can be symptoms of the three other conditions, or numerous others.

Because the symptoms only appear during contact with a particular substance and go away afterward, many ignore the symptoms and continue their daily routine, maintaining their exposure to the illness-causing substances. In fact, as time goes on, people who continually ignore warning signs of repeated symptoms will find themselves becoming increasingly sensitive to many allergens.

The number of crossover symptoms and the possibility of mixing illnesses have made both researching and diagnosing environment-linked conditions problematic. A diagnostic definition of multiple chemical sensitivity was finally put together in 1999, after decades of observing the illnesses and theorizing about it’s environmental cause.

Despite these difficulties, there is hope to treat these conditions. Treatment is a two-step process and involves seeing a professional. First, the patient must attempt to figure out which substance has caused an onset of symptoms. It may be a new window-washing fluid used at the office, or even a new chair. Removing one substance at a time from the patient’s daily environment helps identify the source. Finally, the patient’s daily routine is re-worked so when the substance is removed, regular sleeping patterns are restored and healthy eating habits are implemented.

One thing to keep in mind is that prevention is key. Recognizing that one has developed these symptoms is the first step towards better health.