What does phototoxic mean?
Phototoxic describes a substance, reaction, or effect capable of damaging skin, tissue, or other living material when exposed to light. The damage results from a light-activated chemical process, so the material is not necessarily harmful in darkness but may become dangerous after illumination. The term is especially common in medicine, dermatology, toxicology, and photochemistry. It appears in discussions of phototoxic medications, plant substances, chemical compounds, and reactions caused by ultraviolet light. Phototoxicity should not be confused with photosensitivity: the former specifically indicates that light exposure can produce toxic damage, while the latter more broadly describes a response to light. The word is also useful in scientific and environmental discussions, where it distinguishes light-induced toxicity from toxicity caused by other mechanisms.
adjectiveCapable of causing damage to skin, tissue, or other living material when exposed to light, especially through a photochemical reaction.
- Capable of causing damage to skin, tissue, or other living material when exposed to light.
"Some medications can have phototoxic effects, making the skin more vulnerable to sunburn."
"Certain plant extracts can be phototoxic when applied to the skin before sun exposure."
"The researchers studied the phototoxic reaction that occurs when the compound is irradiated with ultraviolet light."
Some substances become harmful in sunlight: phototoxicity turns exposure to light into a potential source of cellular damage.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does phototoxic come from?
Phototoxic combines the combining form photo-, from Greek phōs, meaning “light,” with toxic, from Latin toxicum, meaning “poison.” The combination expresses the idea of poison or damage activated by light. Related forms such as photic concern light, while toxic, toxin, and toxicant belong to the same poison-related lexical family.
Related word forms
How phototoxic is actually used
Most often used in technical and medical contexts, especially in pharmacology, dermatology, toxicology, and photochemistry. It is related to but not identical with photosensitivity, which can refer more broadly to a light-triggered reaction.
Easily confused with phototoxic
Phototoxic means that light-activated substances cause tissue damage, whereas photosensitive describes a reaction or condition triggered by light without necessarily implying toxicity.