There are currently no clinically valid method to prove a person has MCS, and the disease itself is also controversial. MCS sufferers can look perfectly healthy, and be absolutely miserable, so there is often a lack of legitimacy for others to see. Marriages and friendships have often been lost, as the sufferer has been considered 'getting weird.'
Since the sufferer may have to retract from society to be free of symptoms, social isolation and other psychological problems may arise. The feeling that other people are all enemies are possible.
Consider the scene that you enter a room full of people. You know some people are wearing invisible baseball bats. Some people wear long ones, other short ones. If you get within hitting reach of a person, he of she will hit you with the bat. This is similar to the situation many MCS sufferers experience on a daily basis, when working or shopping. It is nearly impossible to guess who is wearing perfumed products, and who is not, and who wears strong perfumes (the long baseball bat). (There are some clues, but they are far from fool proof). Living in such a nightmare is obviously unhealthy for the soul.
Some scholars have done psychological profiles of MCS sufferers, and found a higher-than-normal number of them have psychological problems. Some go from there to conclude that the psychological problems causes the disease, as we know it is literally possible to think yourself sick. Just think how many old people die shortly after they loose their spouse.
I personally do not believe MCS is a psychological problem, or an odor induced panic disorder, at least not alone. I have sometimes wondered if my own reactions to smells are psychological, and they may be, but the things that do hit me the hardest are those I can not smell at all. Hence I do not seek to get away until I fell the effects, in which case it is too late. Examples of these problems are very low levels of paint fumes, diesel fumes and cigarette smoke.
Hopefully, better diagnostic methods will be available, so this disease can be taken more seriously. It is first recently that tools such as CAT scans have been used to prove migraines, for instance.