Cold-pressed bergamot, lemon, lime, and grapefruit carry furanocoumarins. On skin, then in sun or a tanning bed, they can leave a burn that looks like a spill.
Bergamot FCF (furanocoumarin-free) is the sun-safer bottle. Expressed peel oils are not. Steam-distilled citrus is usually phototoxic-quiet, but check the method on the label.
If you already put expressed citrus on skin, keep that skin covered for twelve hours. Diffusion and inhalers do not carry the same dermal risk.
This is not a ban on grapefruit. It is a reason to put it in the evening blend, or in the diffuser, and leave the midday walk to something else.