Since allergies are not tested, could items show up in the green category even if I have an allergic reaction to the same?

Absolutely they can!

When we test hair samples we are looking at the atom cell structure and how it responds to the different items. When allergies are tested they are measuring the antibodies found in the blood. This means because of the fluidity and quicker replenishment of blood the body can react quicker and more fatally.

Whereas with cellular health, it can take a symptom a longer time to appear, and as such cellular health can indicate more chronic related conditions versus immediate responses that allergies would give.