I would like to know how I can differentiate her everyday eczema from an allergic reaction?

Good evening ma'am,

Eczema is sort of a form of allergy, but at a very low intensity. In other words, the child who is already experiencing a large flare-up of eczema or has eczema all over her body is likely to have come into contact with an ingredient that her body detects as an allergen. In this child, the risk of an allergic reaction is of course still present. When a reaction occurs, the body will first respond by markedly increasing the appearance of the eczema patches.

If the reaction is very strong, then the child could have a "spike" in eczema.