Phototoxins are common in: - a variety of plants (including food
plants where they may be a biological defence): - some
prescribed medications (such as tetracycline antibiotics); and -
many essential oils, perfumes and cosmetics. Ingested
medications may cause systemic photosensitivity and topically
applied medications, cosmetics and essential oils may lead to
local (or perhaps systemic) photosensitivity. Curiously and
ironically, para-aminobenzoic acid (PABA) found in some
sunscreens can also cause photosensitivity. Upon exposure to
light, notably light containing ultraviolet radiation,
discolouration of the skin (whether as inflammation, lightening
or darkening) or rashes may result. In extreme cases, blistering
may also occur. The marigold plant produces the phototoxin
alpha-terthienyl, which functions as a nematicide. When exposed
to near ultraviolet light, such as in sunlight, alpha-terthienyl
generates the toxic singlet oxygen. Alpha-terthienyl results in
damage to the respiratory, digestive and nervous