How do blood tests detect if you’re allergic to something? How does it work?



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I may be wrong but I don’t believe they do. When I got checked for allergies they literally just spread a small amount of various common allergens in specific spots on my back and waited to see which spots got red and itchy. There were no blood tests involved.

An allergy blood test measures a substance called immunoglobulin E (IgE) in your
blood. IgE is an antibody that your body makes. If you have allergies,
you may have more IgE in your blood than normal.

Symptoms of allergies are caused by white blood cells, so they basically look for an increase in those