In addition to what neomi, said, these things provide and broad spectrum of nutrients and enzymes. They nourish the liver, cleanse and revitalize the body.
Also, allergies, especially those one is born with, sometimes are caused by exposure to excess of hormones in the womb. You might want to try iodine (lugol's) to help balance hormones.
As far as herbs, things that helped me a great deal were fenugreek, slippery elm and marshmallow root. Some years ago I was under the care of an iridologist who helped me to very nearly eliminate the food and airborne (dust/mold/pollen) allergies I suffered from. I recall those herbs being very important in the process. Milk Thistle and Dandelion root are also very good for revitalizing the liver. As the liver goes, so does the body.