Once upon a time a long time ago there was a doctor who prided himself on listening to his patients, and treating their illnesses effectively.  As the story goes, he was particularly interested in diseases of the airways, ,and he always carefully listened to the patients story, and he carefully listened to their lungs.  He made many good diagnoses.  Then one day, he heard about a new medical advance--the Chest X-ray--and because he wanted to keep up with his colleagues, he ordered an X-Ray machine and began doing Chest X-rays on everyone who complained of breathing problems.  Gradually, he became fascinated by what he saw on some chest x-rays.  And true enough, they were sometimes very very helpful.  But an unfortunate thing happened.  As the young doctor used more and more x-rays, he began to listen less to the patient's story, and less to their lungs.  One day, a man came into him wheezing, coughing up purulent sputum, and with a fever.  He was very short of breath.  "I have just the test to order" said the doctor.  And he obtained an x-ray.  It showed mild hyperinflation of the lung fields, but nothing more.  He sent the man home without treatment, reassuring him that everything on the x-ray showed really no major problems.  And the man died overnight from progressively worsening asthma. 

...Sometimes I think we allergists are like the young doctor.  We have become so enamored by RAST tests, and measuring IgE antibody measurements, and so quick to say a patient has "no problem" or "no allergy" when they react to a food or a substance by history, that we make tragic mistakes.  The history, and provacative challenges are the "Gold Standard".  

Ishizaka's discovery of IgE was the BEST thing--and the WORST thing--for the allergy profession.