According to the MayoClinic, food allergy is a problem that affects between 6 percent to 8 percent of children and 4 percent of adults. While most food allergies are related to milk, eggs, nuts, fish, shellfish, soy and wheat, an allergy can develop to any food, including broccoli.
An allergy to broccoli develops when a person's immune system erroneously determines that the broccoli is a foreign and potentially harmful substance. The immune system forms antibodies known as immunoglobulin E, or IgE, to the broccoli. When the person later ingests broccoli again, the IgE responds to the presence of the food and releases chemicals that result in the symptoms of an allergic reaction.
Symptoms of broccoli allergy typically occur minutes to an hour after the ingestion of broccoli or a food that contains broccoli. These symptoms include tingling or itching of the mouth, a skin rash or hives, swelling of the lips, hands or feet, difficulty breathing, cough, nausea, vomiting and dizziness. Any combination or all of these symptoms may occur in the setting of an allergic reaction. A severe allergic reaction known as anaphylaxis can also occur. This is a life-threatening reaction that involves throat constriction, difficulty breathing, and dizziness with decreased blood pressure.
In some people, symptoms of an allergic reaction occur when broccoli is ingested because of the salicylate content of broccoli rather than because of the broccoli itself. According to the Cleveland Clinic, salicylates are chemicals found in all plants and that in some people, even small amounts of salicylates may result in an allergic reaction. A person with salicylate sensitivity will likely also notice symptoms with other foods that contain salicylates, such as apples, avocados, strawberries, zucchini, coffee and nuts.
A careful history in which the physician listens to the series of events that led to the allergic reaction can often help to make the diagnosis of a broccoli allergy. In addition, an allergist can perform a procedure known as a prick to prick test. In this procedure, the skin is scratched with a small amount of fresh broccoli and any reaction is measured.
The primary treatment for broccoli allergy is avoidance of broccoli and any food products containing broccoli. In the event of an accidental exposure, an antihistamine such as benadryl can be used for a localized skin reaction such as itching. For a more systemic reaction that involves difficulty breathing, vomiting or dizziness, injectable epinephrine should be used to reverse the reaction. If injectable epinephrine is used, the person should immediately go to the emergency department for further evaluation.