These reactions are not related to pesticides or metals. Oral allergy syndrome is nearly always preceded by hay fever and tends to occur most often in older children and adults. These reactions can occur at any time of year, but are often worse during the pollen season involved. Symptoms may include itching and burning of the lips, mouth and throat, watery itchy eyes, runny nose and sneezing. Some individuals report that peeling or touching the offending foods may result in a rash, itching or swelling where the juice touches the skin.
More serious reactions can include hives and swelling of the mouth, pharynx and windpipe.
In rare cases, severe allergic reactions have been reported such as vomiting and diarrhea, bronchial asthma, generalized hives and anaphylactic shock. Symptoms usually develop within minutes of consuming or touching the food, but occasionally occur more than an hour later. A variety of fruits, vegetables and their juices, including orange, tomato, apple and grape, sometimes cause skin rashes and diarrhea, especially in young children. Foods associated with birch, ragweed, grass and mugwort pollen are listed in the following table. The main exceptions to this are celery and nuts which may cause reactions even after being cooked.