Additives and my child's behaviour

Could food additives be affecting my son's state of mind and behaviour? It's a frightening thought, but having read up a little, I'm concerned about the impact of junk food even beyond its hopeless nutritional value.

It began last weekend when Ben spent an hour or so acting very out of character. Unlike a temper tantrum, he didn't seem angry, but was pretty much out of control. Almost like being drunk, but with a three year old's energy! After a while it transpired that he'd been given (by my husband) a shop-bought cupcake with "very fake looking" icing.