Citral

It’s a common fragrance ingredient that smells like lemon and has a bittersweet taste.  It can be found in many plant oils, e.g. lemon, orange, lime or lemongrass. 

It’s one of the “EU 26 fragrances” that has to be labelled separately (and cannot be simply included in the term “fragrance/perfume” on the label) because of allergen potential. Best to avoid if your skin is sensitive.