In pharmacology, a photosensitizer is a drug, food, or other chemical that increases photosensitivity of the organism. This may be an adverse effect of many drugs, or a desired effect in photodynamic therapy of tumors.

In photochemistry, a photosensitizer is a chemical compound that readily undergoes photoexcitation and then transfers its energy to other molecules, thus making the reaction mixture more sensitive to light.

See also

• Sensitiser