For some people, biting into a perfect sun-ripened peach can lead to strange, itchy sensations in the mouth and throat. This is the body's way of defending itself against what it perceives as foreign invaders. In the case of fruits, the invaders are proteins on the fruit's skin that resemble pollen, and trigger an allergic reaction.
The condition is known as oral allergy syndrome, or pollen-food syndrome. It more frequently occurs in people who already have known pollen allergies. And depending on the type of pollen allergy, the food that triggers the oral allergy may be different. For example, people allergic to birch pollen can have itchy mouth reactions to peaches, pears, plums, and even celery and apples. Ragweed pollen allergies are typically associated with cross-reactions to bananas, cucumbers, melons, sunflower seeds, and zucchinis.
Fortunately, oral allergy syndromes are often less severe than true food allergies - the itching usually goes away after a short while. Furthermore, the reaction can be bypassed by removing the fruit skin, or by cooking the fruit to denature the offending proteins.