The oral allergy syndrome is difficult to detect. Common allergy tests to examine allergy are using extracts only in skin scratch testing. But this method is quite useless due to many enzymes involved in allergy reaction are already broken out in the process of extraction. They are not as effective as the original enzymes. Oral Allergy Syndrome is usually diagnoses by symptoms that are appeared. The other method is to look for allergy history to pollen, if any.
Oral allergy syndrome symptoms are caused by a rapid response of the mast cell–bound pollen-specific IgE to allergens released from raw fruits and vegetables as they enter the mouth and come into contact with saliva. Unusually high concentrations of mast cells in the oral and pharyngeal tissues result from continual response to pollen allergens in their native form. The tissues of the upper respiratory tract become sensitized to a pollen allergen as both cause and consequence of long-standing hay fever.
Foods that contain a protein that is structurally indistinguishable from the allergenic protein in the pollen can cause release of inflammatory mediators from the primed mast cells. For example, the food allergens can attach to the pollen IgE molecules sitting on receptors on the mast cells and act as if they were pollen proteins.
The released inflammatory mediators then affect tissues adjacent to the upper respiratory tract in the oral cavity and cause inflammation.
Interestingly, the proteins in foods that can mimic pollen proteins come from plants that are botanically unrelated to the plants that produce the pollens. This is further evidence that botanic relatedness has little or nothing to do with antigenic (or allergenic) relationships, and shows that the old idea that allergy to foods in one plant family predicts allergy to other foods in the same plant family is mostly invalid.
