Photosensitivity

In medicine, increased sensitivity of the skin to light and other sources of UV. Photosensitivity commonly causes reddening and blistering of the skin with exposure to sunlight and, in time, it heightens the risk of skin cancer. A number of diseases make for photosensitivity, as do scores of prescription and non-prescription drugs. (For details, see Sunburn and Sun-Sensitizing Drugs). The eyes may also be oversensitive to light, a condition called photophobia, as occurs for example in measles. In biology, photosensitivity need not be abnormal. It refers to the fact of being readily stimulated by light.

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Abnormal sensitivity to light, especially of the eyes. For example, light may irritate the eyelids, conjunctiva, cornea or, in excess, the retina; when scattered by a cataractous lens light may produce glare; it can produce a migraine headache or a temporary exotropia. See photophobia, photalgia, photesthesia.

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n.

abnormal reaction of the skin to sunlight. This characterizes certain skin diseases (see photodermatosis). Photosensitivity reactions may also occur in those taking such drugs as tetracyclines, phenothiazines, furosemide, amiodarone, and NSAIDs. In these cases the effect may resemble severe sunburn.

• photosensitive adj.

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pho·to·sen·si·tiv·i·ty (fo″to-sen″sĭ-tivґĭ-te) [photo- + sensitivity] 1. ability of a cell, organ, or organism to react to light. 2. an abnormal response of the skin or eyes to sunlight, involving the interaction between photosensitizing substances and sunlight or filtered or artificial light at wavelengths of 280–400 nm. There are two main types: photoallergy and phototoxicity.

Photosensitivity. Severe sunburn in exposed areas after application of a topical photosensitizing cream and exposure to the sun, with sparing of areas under the bathing suit.