I would like to discuss food allergy in adults, and symptoms that one may experience with food allergies. Fortunately, food allergy is pretty rare in adults, only about 1-2% of the adult population has true food allergies. (However, many other adults have what we call, food intolerance, which is a different mechanism than a true allergy, and may include lactose intolerance). Food allergy is much more common in children, but fortunately some children outgrow their food allergies.
The typical symptoms of food allergy are varied, and usually develop within 15 to 30 minutes after eating the particular food. Therefore, if your symptoms develop more than 1-2 hours after eating the food, it is less likely that you may have food allergies, and it may be a food intolerance instead. The usual symptoms include hives, itching, nausea, vomiting, feeling lightheaded, abdominal pain, swelling of the lips/tongue and in some cases difficulty breathing. If you experience any swelling of the lips and/or tongue and notice that you can not breathe or your voice changes, you should immediately go to the emergency room as this reaction may be life threatening.
The foods that adults may be allergic to are generally tree nuts (such as almonds, pecans, walnuts, etc.), peanuts (which are actually in the legume or bean family), shellfish, and finned fish (i.e., tuna, salmon). Children tend to be more allergic to foods including eggs and milk, and fortunately usually outgrow these food allergies by ages 2-3 years. However, if a child develops allergies to the foods mentioned above for adults (nuts, peanuts, shellfish and finned fish), it is less likely that he or she will outgrow these allergies and will have them as an adult. It is also not unusual for an adult to develop food allergy, and no one really knows why this happens.
If you think that you may have a food allergy, the most important thing to first do is to avoid this food until you visit the allergist. Even eating a small amount of the food may cause a life threatening reaction, especially with peanuts or tree nuts. It may also be a good idea to bring the wrapper of the food which you ate, if it were a prepared food; this will allow the allergist to see the label as well. When you visit the allergist, he or she will most likely do a skin test and/or a blood test to see if you are allergic to this food. If the results of these tests suggest that you are allergic to the food, you must strictly avoid this food. The allergist will also go over with you measures that you can take if you eat this food by accident which may include taking an anti-histamine and purchasing a preloaded syringe with epinephrine. You should carry with you these "rescue" medications, as you never know when a reaction may happen. It is also critical at this point, that you read food labels, as many foods may contain trace amounts of the food to which you are allergic. Fortunately, food labels have been made easier to read for the general public to let people know if the food contains items such as peanuts or tree nuts. Also, if you are allergic to a food, you need to be careful when going to restaurants and over to friends houses to eat and ask about the ingredients. It is also important to ask the allergist about eating foods that may "cross-react" with the food to which you are allergic. For example, if you are allergic to one of the tree nuts, you may also be allergic to another type, or if you are allergic to lobster, you may also be allergic to another shellfish. In addition, some patients who are allergic to outdoor pollens, may also develop itching of their mouth when they eat certain fruits. This is called the oral allergy syndrome and you should talk with your allergist about this.
I hope that this short blog gives some insight into adult food allergy. However, I wish to stress, that it is not meant to replace a visit to the allergist, as food allergies can be life threatening. If you have further questions, please let me know.