It doesnt' even have to be an "allergy" but rather simply a sensitivity. A large, well-controlled British study a few years ago showed that people who are prone to hyperactivity clearly become worse when exposed to a few common food dyes and preservatives. http://www.time.com/time/health/article/0,8599,###-###-##...
My own experience is that quite a few chemicals are capable of causing nervousness, sleeplessness, mood swings, dizziness, and a whole assortment of nervous-system disruptions in sensitive people. I used to participate in group sensitivity testing at my doctor's office, and I would watch calm children go manic within a couple of minutes of having various very dilute chemicals squirted under their tongues.
I have very noticeable emotional and physical changes occur when I've gotten exposures to a range of chemicals, some of the worst being the scents in laundry products and air fresheners. One concentrated whiff can keep me from sleeping well for as long as three or four nights.