Allergy to veneers, crowns? Is it possible that I am reacting to the cement used to adhere the veneers and crowns?

It is possible that you are allergic to either the cement or the bonding materials.  There are many chemical groups in dental materials.  Patients who are highly sensitive may want to consider doing a Clifford Test prior to having their work done.The Clifford test is a blood test that evaluates your blood for reacting to different chemical groups.  It then lists dental materials as S or satisfactory if they do not have chemical groups you react to.I do not use it universally and usually use prior to doing work on sensitive individuals.  You could do the test now that your veneers are bonded in but if the materials are not satisfactory the only recourse would be to redo them.In most patients this  is not a problem.  In extremely sensitive patients even changing the color of a cement may be enoug to provoke a reaction.This information is from the website:Clifford Materials Reactivity TestingClifford Materials Reactivity Testing (CMRT) is a laboratory screening process used to help identify existing sensitivity problems to various chemical groups and families of compounds in an individual patient. This process is currently being implemented in the CMRT Dental and Orthopedic panels. After a patient's test panel has been completed, the patient's reactivity test results are compiled in a report.Dental Materials Screening PanelScreening for systemic sensitivities to more than 16,003 trade-named products and 94 chemical groups and families of dental products.Orthopedic Materials Screening PanelScreening for systemic sensitivities to more than 5,652 trade-named products used in surgical aplications.

Anything is possible but allergies to veneers or crowns is highly unlikely. If the crowns have metal underneath the porcelain you can be allergic to that.  But, it would be extremely rare to be allergic to porcelain or cements.