This is only important if the constituent are going to be in contact with the skin. This goes for putting the lemon oil in carrier oils as well as diffusing the lemon oil. Some lemon essential oils have more dosages of the constituents that can irritate the skin and others not so much. Some leon oils are more focused on solvents used in cleaning products. As you can see in my videos, some lemon oils eat up the styrofoam cup muchc quicker than others. Also some oils are can lead to more phototoxicity than others.
If looking to use the oils on my skin I look for the oils with the least amount of furanocoumarins. These are what react when in the sun from the UV light
Note: The same oil can be steam distilled or cold pressed. The cold pressed oils are usually the most phototoxic unlike the steam distilled version. There are a lot of lemon oils I have and some of them say steam distilled and cold pressed on the bottle. This is the first thing I look for before smelling the oil.
Also the constituent profile is different the way the oil was distracted too.