Why do some plants cause allergy problems and others do not?
For a plant to cause allergy problems the pollen must to able to get to the persons immune system. Plants that do not have pollen or whose pollen is not airborne, but rather is transferred by insects do not cause allergies (most flowers and fruit trees). Once the pollen is airborne and comes in contact with the mucosa (lining) of the nose, eyes, throat, chest and in some cases the skin the protein in the pollen must be water soluble to pass into the inner linings so that it can stimulate the immune system. The size and quantity of the pollen protein is also important in determining if there will be allergic reaction. The final and most important part of the reaction is the individual’s immune system and the control mechanisms determining if and how a reaction will occur. Much present and future research is aimed at identifying and learning how to control those mechanisms.