Dr. Adrian Y. Y. Wu in the Prince Bldg., Central (Tel: 28180180) was good for us, we recently tested our bub for the full range of foods as she was getting lots of unexplained rashes. She actually wasn't allergic to anything! The verdict was viral reaction.
When she was younger and had just started on solids (6 months) we also went for NAET with a therapist called Ann at The Body Group - a homeopathic/non invasive allergy test/treatment (hubby thought it was a little 'left field', but I thought it was definitely useful)