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Photodermatoses

Photodermatoses (from Greek photos – light and derma – skin) present a large group of skin diseases caused by the exposure to the sunlight with various clinical manifestations, severity and prognosis.

There are 3 types of ultraviolet (UV) radiation:

  • C – short-wave radiation (the wave length of 100-280 nm), which is captured by the ozone layer of the stratosphere.
  • B – short-wave radiation (290-320 nm), which plays an important role in the development of sunburns and skin cancer.
  • A - long-wave radiation (320-400), that plays a great role in the development of skin cancer. It contributes to suntan but without the formation of burns.

Types of photosensitivity of the skin

Type 1.  Irrespective of the color of the eyes or hair, a person receives a sunburn 30 min after sunbathing and never becomes tan.

Type 2.  A person gets sunburns easily but it is difficult for him/her to become tan.

Type 3.  Sunbathing causes slight sunburns, which develop into a tan, sometimes, rather intensive.

Type 4.  A person becomes suntanned easily without getting sunburns.

Type 5.  People with dusky complexion belong to this type.

Type 6.  People of the Negroid race belong to this type.

There are 4 main types of the body response to the light exposure:

  1. Photo-traumatic reactions caused by the excessive radiation of the skin or when it becomes excessive due to the lack of natural defense factors.
  2. Photo-toxic (or photo-dynamic) reactions related to the presence of some chemical substance in the body having the properties of a photo-sensitizer.
  3. Photo-allergic reactions in the form of classic immunologic response to an antigen formed under the exposure to light.
  4. Other types of reactions with the unknown causes (idiopathic photo-dermatoses).

Possible photo-sensitizers:

  • medical, such as antibiotics (tetracyclines, sulphanilamides, fluoroquinolones), non-steroidal anti-inflammatory drugs, diuretics, the drugs lowering the level of blood glucose, as well as statins, neuroleptics, hormonal therapy and oral contraceptives;
  • dietary, such as hen’s eggs, figs, citrus fruits (especially, grapefruits), parsley, dill, carrots, parsnip;
  • herbs, such as angelica, green wheat, barley, fig’s leaves, melilot, clover, ginkgo biloba, mustard, green onion, garlic, agave and St. John’s wort.
  • some acne remedies, after shave, perfumery (soap including) and cosmetics.

Photo-traumatic reactions are observed in solar (actinic) keratosis. This is a limited skin neoplasm developing in people with phenotype 1-3 after excessive sunbathing during a short period of time (acute actinic keratosis) or in those who received excessive UV radiation during all their life

(chronic actinic keratosis) due to their occupation (sailors, farmers, drivers). Multiple rough foci of 1-2 mm appear on the dry and hyper-pigmented skin aging under the UV exposure. The edges of the foci are irregular and protrude a little over the skin surface. They can be flesh-colored, pink or dark with the formation of telangiectasis. The surface is covered with yellow or brown scales. On removing the scales, small painful, slightly bleeding erosions are formed. The foci are usually located on the open skin areas, such as the face (mostly, the forehead, cheeks, nose and ears), the back of the wrists, arms, sometimes shoulders, as well as the scalp in men with untimely baldness.

           Photo-toxic reactions. Photosensitizers can penetrate the skin endogenously, that is, with the medicines and food supplements; or exogenously, as a result of a direct contact with the skin (cosmetics, drugs, herbs). Clinical manifestations are usually limited by the exposed area (the face, ears, low neck, wrists, etc.). The reaction is seen immediately after the UV exposure and characterized by burning, pain, erythema, swelling and vesiculation. Delayed reactions may sometimes appear 8-24 hours following the exposure.

Possible clinical manifestations of photo-toxic reactions:

  1. pigmented photo-dermatitis caused by using perfumes containing bergamot essence;
  2. phyto-photo-dermatitis observed 24-48 hours following the contact of the skin with sensitizing plants (lime, lemon, figs, celery, carrots, cow-bream, etc.) and exposure to the sunlight with the formation of vesicles;
  3. photo-onycholysis as a result of taking tetracyclines. It is manifested 3-6 weeks following the treatment by dimmed nail plates and hyponychial hyperkeratosis beginning from the lateral edges of the nails. This can lead to the nails detachment.

Photo-allergic reactions.   This is a form of immunologic reaction. It only occurs in people with confirmed sensitization to some medicines. Skin eruptions usually appear 48 hours after the contact between the chemical substance and the light. The first clinical manifestations include the appearance of vesicles and blisters followed by the formation of crusts and peeling. Sometimes, skin eruptions spread to the neighboring areas. The skin reaction usually lasts during a week after the drug discontinuation, but sometimes it becomes chronic (stable light reaction).

 Solar urticaria occurs 5-10 min after the exposure to the sun (sometimes, to the artificial light source). The patients complain of itching, erythema, single or merging blisters that disappear spontaneously in an hour time. The disease usually develops on the  exposed skin, with rare foci appearing on the skin covered with the clothes if they transmit enough light.  Skin areas exposed to chronic UV radiation (the face, the arms) are usually less vulnerable as compared with those that are covered with clothes.

Prophylaxis of photo-dermatitis. Many people who experienced “the sun allergy” even once are sure that sunbathing is forbidden for them. This is not so. Observing certain rules, sunbathing is possible. As for children, they often outgrow  allergies.

Some rules of sunbathing in photo-dermatitis :

  1. Minimize the use of perfume and cosmetics when you sunbathe.
  2. It is necessary to wear a wide-brimmed hat, sun-glasses and to use high protection sun cream.
  3. Limit the duration of sunbathing. The best time is from 6 to 10 a.m. and from 4 to 7 p.m. During the hot period of the day, it is better to be inside or to wear light clothes with long sleeves and to sit in the shade.
  4.  It is not recommended to perform serious cosmetic procedures before going to sea, such as face polishing  and peeling, or to use medicines increasing the skin sensitivity to the UV.
  5. If you have just stopped taking the medicines, study carefully the leaflet or consult the doctor trying to learn if your medicine affects photo-sensitivity.

Observing these simple rules, you can sunbathe without any troubles (such as sunburns and photo-dermatitis) and even forget for a short time that the sun may be harmful for your skin. 

T.A. Pivovarova, Head Doctor of the Dispensary.