RAST is not as sensitive as skin prick tests for picking up food allergies, according to my allergist. He said that foods have more than one recepter site for generating a reaction but that RAST may not detect reactions to all of the receptor sites on a particular food. The skin test doesn't have this same limitation since it is done directly on your body and you will generally respond to any of the recepter sites available.
That said, test serums are not standardized, so the serum concentration used for your RAST test may have been more diluted (lower concentration of active allergen) than what was used for your skin test and thus returned negatives for foods that did react on your skin.
Also, there is always the possibility of false negatives and false positives ~ results that say one thing when the opposite is actually true. So always interpret results from allergy testing within the context of your particular symptoms. Keeping a food diary while still eating the possible allergen foods is one way to observe patterns so that you can determine whether or not the test results seem accurate. Note every ingredient of every food and liquid you eat/drink, plus the time of day, and then note any changes in symptoms & the time of the start & end of the symptom(s).
I hope this helps - take care,
Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD (Lupus?), Osteoporosis, Anemia, T- & B-Cell Lymphopenia, malabsorption/malnutrition, Lyme Disease (Igenex Lab IgM WesternBlot positive/CDC negative), etc.
Meds: Pulmicort, Injectable Vitamin B12, Herbs, Nutritional Supplements, Homeopathy.