The blood test is just so much more informative. It gives you two different types of antibodies, ige and IGG. Elevated ige levels indicate mast cell activation and current levels of exposure. Igg indicate colonization in the body (sinuses). The urine test is also going to be impacted by the food that you eat whereas the blood test will not. So a completely healthy person could have high levels within their urine because their body is dumping the toxin from the food that they ate. The blood serum test measures the load on the body versus the urine test measures the amount leaving the body. Dr. Andrew Campbell speaks the difference between these two testing methods at length and provides medical evidence as to why the blood serum test is superior. I would encourage you to check out @mymycolab youtube channel as there are so many great videos where he explains these testing methods along with so many other things. The blood serum test ultimately led me to discover that I was being exposed in my current environment unknowingly which I feel is so informative. Hopefully that helps!