Wow, some just really don't get it...
Ok, so you've got Team A - adamant that she's suffering from nothing but chemical sensitivity (20th Century disease). Then you've got Team B - adamant that it's all just a symptom of her banal existence and that she's imagining it to fill the void in her vacuous life.
Then there's the rare few who see what Haynes was really trying to convey. It's a very grey area. Her symptoms prove to be very real in a lot of scenes which supports the theory she is genuinely chemically sensitive, but this doesn't detract from the fact she is searching for meaning in her painfully superficial existence. She experiences a brief glimmer of hope when she discovers Wrenwood only to find the same superficiality in a different form. The scene where the "cult" leader gives the first speech Carol witnesses is one of the most bone chilling moments I've seen in film. The look on her face doesn't hide the fact that she's thinking, Oh my Lord, what have I let myself get sucked into here? She sticks it out and gets sucked further in, culminating in her big move into the ceramic bubble looking at her own reflection, completely devoid of any self identity and more alone than she ever was before. Poetry in film...