There are many misconceptions about chemical sensitivities. Near the top of the list is that chemical sensitivities are a form of allergy.
There are technical differences between allergies and chemical sensitivities, and those are important when dealing with doctors, but there are two practical, everyday reasons to not confuse chemical sensitivities with allergies.
The first is this: though people may get an understanding of what kind of distress you are trying to describe, they will likely expect you to take an antihistamine and get on with your life. Antihistamines may provide a little relief of some symptoms, but many people with chemical sensitivities cannot tolerate them so they will tend to feel worse.
The other is that many treatments designed for allergies are not designed for chemical sensitivities. In fact, some allergy treatments can be harmful for those who suffer chemical sensitivities. Provacation and neutralization comes immediately to mind.
-That's all for now.