Photosensitivity (dermatology)

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Classification according to ICD-10
L56.8 Other specified acute skin changes from ultraviolet rays
ICD-10 online (WHO version 2019)

In dermatology, photosensitivity , also called photosensitivity , is a pathological sensitivity to light.

When exposed to light , photosensitivity results in photodermatosis : even after low levels of light exposure , photosensitized skin develops excessive sunburn, a rash or symptoms such as itching, burning or paresthesia .

Causes of Photosensitivity

The exact cause and development of photosensitivity cannot always be determined. Some diseases have photosensitivity of unknown cause as a symptom, e.g. B. lupus erythematosus .

Photosensitivity triggers can be minimal chronic skin damage caused and maintained by certain diseases, e.g. B. DNA damage in Xeroderma pigmentosum .

Photosensitivity can also be triggered by photosensitizers. This is understood to mean substances that are stored in the skin and cause increased sensitivity to light there.

  • The body can produce photosensitizers itself in certain diseases: They are called endogenous photosensitizers. When exposed to light, these can lead to secondary photodermatosis via photosensitivity . Diseases that produce endogenous photosensitizers include e.g. B. Porphyry .
  • Photosensitizers can be foreign substances that are supplied to the body either externally, through direct contact, or internally. These are called exogenous photosensitizers. When exposed to light, these exogenous photosensitizers can lead to primary photodermatosis via photosensitivity . Common exogenous photosensitizers are certain drugs, but also other substances, e.g. B. skin creams, cosmetics, sunscreens, dyes or perfumes.
The photosensitivity caused by exogenous photosensitizers can manifest itself as phototoxicity or photoallergy . Photoallergy usually occurs as a contact allergy . It is not always possible to differentiate between phototoxic and photoallergy, as some substances have both phototoxic and photoallergic properties.

Diagnosis of photosensitivity

Graduated exposures in the UV-A and UV-B range in the form of a light staircase are suitable for clarifying photosensitivity . The minimum erythema dose (MED) is typically reduced. A pathological decrease in the minimum erythema dose in skin types I and II is assumed for values ​​below 10 J / cm² UV-A and 0.025 J / cm² UV-B. For skin types III and IV, a minimal erythema dose of UV-B below 0.075 J / cm² is considered suspect.

Photosensitizers with a phototoxic effect are detected by first showing the photosensitivity through a staircase of light, then omitting the substance and checking the photosensitivity again after a while.

Photosensitizers, which cause a photoallergic reaction, are detected by a patch test with exposure.

Prevention and therapy for photosensitivity

Glass and thin clothing largely block UV-B radiation , but not UV-A radiation . Reactions of photosensitized skin can therefore also occur behind glass panes when exposed to the sun.

Sun avoidance and sun protection are preventive and therapeutically effective in the case of photosensitivity . It is helpful to avoid solariums, wear tightly woven clothing, sunscreens against UV-B and UV-A radiation with a high sun protection factor (at least 30) and UV-impermeable films on the windows.

Drugs that have a photosensitizing effect should, if possible, be discontinued or reduced in dose after consulting the attending physician. Other photosensitizing substances should be avoided.

If even the briefest exposure to the sun acts as a trigger for dermatosis , desensitization through phototherapy can be helpful.

In the acute case triggered by photosensitivity, topically applied cortisone ointments can help.

See also

literature

  • KH Kaidbey, AM Kligman: Identification of topical photosensitizing agents in humans. In: Journal of Investigative Dermatology. Volume 70, No. 3, 1978, pp. 149-151.

Individual evidence

  1. ↑ Alphabetical directory for the ICD-10-WHO version 2019, volume 3. German Institute for Medical Documentation and Information (DIMDI), Cologne, 2019, p. 699
  2. ↑ a b c d W. Pschyrembel: Clinical dictionary. 257th edition. Walter de Gruyter, Berlin / New York 1994, ISBN 3-11-012692-3 .
  3. ↑ a b c d e What to do in case of photosensitivity? ( Memento of the original from October 29, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on: gfi-online.de , accessed on September 8, 2013, from: WL Morison: Photosensitivity. In: New England journal of medicine. 350, 2004, pp. 1111-1117. @1@ 2Template: Webachiv / IABot / www.gfi-online.de
  4. ↑ a b c d e f g h i Silvia Schauer: When drugs and light are incompatible. Retrieved September 8, 2013 .
  5. ↑ AWMF online: Recommendations for carrying out photo tests if photodermatoses are suspected. (PDF; 305 kB) Retrieved September 22, 2013.
  6. ↑ Gerd Kindl: Before the skin burns. from: pharmische-zeitung.de , accessed on October 1, 2013.