While many people experience adverse reactions to certain foods or food additives, only a small percentage of these are actual "allergic" reactions. Most adverse food reactions are considered an "intolerance," that, while often unpleasant, is not life-threatening. Allergic reactions occur when the body's immune system releases IgE, a protein that causes a cascade of other immune reactions within 2 hours of exposure to the inciting substance. Red #40 food dye causes both types of reactions in some hypersensitive individuals, especially children.
The skin may become itchy or red, and may have rashes such as hives, which are raised itchy bumps, or eczema, which is swelling and itching with the appearance of lesions oozing a clear fluid. Angioedema is a more dangerous type of swelling characterized by swelling in the deep layers of the skin; it may also appear at the surface of the skin as raised welts. It can occur anywhere on the body, but is often first visible around the face, eyelids and tongue.
Gastrointestinal symptoms are common to both allergic reactions and food intolerances. They may include stomachache, diarrhea, and nausea with or without vomiting. Gastrointestinal symptoms may be the only symptom in the case of food intolerance, but are generally associated with the prior appearance of skin and respiratory symptoms in an allergic reaction.
Respiratory symptoms are due to inflammation in the airways. Wheezing, or a whistling sound in the chest, and general nasal congestion are common respiratory symptoms.
People may experience feelings of lightheadedness, dizziness or actual fainting.
Anaphylactic shock is the most severe type of allergic reaction, and can result in death if not immediately treated with epinephrine and skilled emergency care. It is characterized by most of the previously listed skin and respiratory symptoms, plus severe swelling over the entire body. The swelling results in difficulty swallowing and breathing. There is a rapid pulse, dizziness, lightheadedness, a bluish color to the skin and eventual loss of consciousness.