Though it is relatively rare, some people are allergic to tomatoes and can experience a number of unpleasant symptoms when they eat them, particularly if they are raw. Symptoms usually arise initially in and around the mouth, with the lips, tongue, and throat first becoming itchy and then often swelling. Some people may also develop hives or an itchy rash on other areas of the skin. Gastrointestinal symptoms are also common, including nausea, vomiting, and diarrhea. A more severe, systemic reaction can cause difficulty breathing, fainting, and even anaphylactic shock or death.
The first place that symptoms of a tomato allergy often show up is the area first exposed: the mouth. Often the allergic person will start feeling itchy on and around his or her lips, on the tongue, and even in the throat shortly after eating. This is frequently followed by swelling in the same areas. Swelling in the throat can be particularly problematic, as it may make breathing difficult.
A tomato allergy can also cause a reaction on skin elsewhere on the body. Some people develop itchy hives that can arise on some or all of their skin. They may also get a rash, which can be persistent if they do not take tomatoes out of their diet.
During an allergy attack, the body may try to rid itself of the allergen with a gastrointestinal reaction. The allergic person may feel nauseous and start to vomit to get the tomato out. He or she may also have diarrhea as part of the body's response.
In some cases, an allergy to tomatoes can be severe and lead to serious symptoms. It is also quite common for the allergic reaction to start out fairly mild and get progressively worse with each subsequent episode. Those who do have a severe tomato allergy may wheeze and have difficulty catching their breath. This can lead to a loss of blood pressure, which can make the person dizzy and faint. If he or she does not get medical attention quickly, the reaction may eventually result in anaphylactic shock, heart or respiratory failure, and even death.
People with tomato allergies may also want to use caution when ingesting plants from the same family. Two closely related foods that commonly cause symptoms in those with a tomato allergy are potatoes and eggplant. Tobacco is also closely related to the tomato, so smoking can also sometimes lead to an allergic reaction.