why is a chemically sensitive person not able to build an immunity to perfume?

what does "immunity" mean?

See the second definition.

http://dictionary.reference.com/browse/immunity

i understand what immunity means now, but i still don't know how to answer this question.

http://txeh.org/What%20Is%20Chemical%20Sensitivity.htm

yeah like i know what chemical sensitivity is but i just don't undertand what the question is asking

I don't know how to simplify this question any further. Sorry.

A chemically sensitive person may not be able to build an immunity to perfume because the reactions they have are not due to an immune response, but rather a sensitivity or intolerance to certain chemicals present in perfumes. This type of sensitivity is not the same as an immune response, where the body recognizes and responds to harmful substances in an attempt to protect itself.

In general, "immunity" refers to the ability of the body's immune system to recognize and defend against harmful substances like bacteria, viruses, or other foreign agents. Our immune system is designed to differentiate between harmful substances and harmless ones and produce an immune response when necessary. This immune response can involve various mechanisms such as producing antibodies, activating immune cells, or triggering inflammation to neutralize or eliminate the threat.

However, sensitivities or intolerances to certain substances, like perfume in the case of chemically sensitive individuals, typically involve a different mechanism. Instead of involving the immune system, these reactions are often the result of a heightened sensitivity or intolerance to specific chemicals. The effects can vary from person to person, but may include symptoms such as headaches, dizziness, nausea, or respiratory difficulties.

Therefore, the inability to build an immunity to perfume in chemically sensitive individuals is because their reactions are not driven by the immune system, but by the individual's unique physiological response to specific chemicals.