Why does skin react to the sun?
Ultraviolet light changes the structure of some molecules in the skin, and the immune system begins to perceive them as foreign. This is how polymorphic photodermatosis develops - the most common form that occurs at the beginning of the season, when the skin is not yet adapted to the sun. A separate mechanism is a phototoxic reaction: a substance on the skin or in the blood absorbs ultraviolet light and damages cells directly, with a reaction similar to a severe sunburn and occurring in anyone with a sufficient dose. A photoallergic reaction develops only in those who are predisposed and resembles eczema.
- Polymorphic photodermatosis is the most common form
- Phototoxic reaction - similar to a severe burn
- Photoallergic reaction - eczema type
- Solar urticaria - blisters in the first minutes of exposure to the sun
- Exacerbation of chronic skin diseases under the influence of ultraviolet radiation
What triggers the reaction
Very often medications are to blame. Tetracycline antibiotics and fluoroquinolones, some diuretics and blood pressure medications, nonsteroidal anti-inflammatory drugs, St. John's wort, and retinoids can increase sensitivity to the sun. The second large group is substances that come into contact with the skin: juice of hogweed, parsley, figs, citrus fruits, bergamot essential oils, perfume components and some sunscreen filters. Contact with plant sap in the sun produces characteristic stripes and spots with blisters - the so-called meadow dermatitis.
- Antibiotics of certain groups and sulfonamides
- Diuretics and some blood pressure medications
- Nonsteroidal anti-inflammatory drugs
- Retinoids and St. John's wort preparations
- Juice of hogweed, parsley, figs, citrus fruits
- Perfumes and essential oils on the skin
- Beauty treatments just before the sun
Symptoms
Rashes appear only where the sun hits: on the face, neck, décolleté, outer surface of the forearms and legs. Areas covered by clothing remain clean, and this clear boundary is an important diagnostic sign. The rash occurs in the form of small nodules, blisters, merging red spots, accompanied by itching and burning. With polymorphic photodermatosis, it appears within a few hours and lasts for several days. Over time, with regular, dosed exposure to the sun, the skin often adapts, and by mid-summer the reaction weakens.
- Itching and burning of exposed skin
- Small nodules, blisters, red spots
- Clear boundary along the clothing line
- Swelling of the eyelids and face
- The appearance of a rash a few hours after sun exposure
- Repeating the reaction every season
Diagnostics
Diagnosis is usually based on the typical pattern and association with the sun. The doctor asks in detail about medications and supplements taken, cosmetics, perfumes, gardening and contact with plants, and clarifies how long it takes from exposure to the sun to the appearance of a rash. A general blood test helps assess your general condition. If the rash is persistent, there is joint pain, weakness, hair loss, the doctor rules out systemic lupus erythematosus and other autoimmune diseases. If there are severe blisters, dark urine and abdominal pain, porphyria is checked. Photo tests are carried out in specialized centers.
- Examination by a dermatologist to assess the location of the rash
- Detailed analysis of medicines and cosmetics
- General blood test
- Screening for autoimmune diseases if suspected
- Allergy examination for concomitant reactions
- Photo tests in specialized institutions
Treatment and prevention
The first thing is to stop irradiation and cool the skin with a cool compress. Externally, the doctor prescribes anti-inflammatory drugs; in case of severe inflammation, a short course of external glucocorticoids; orally, if indicated, antihistamines. If a provoking drug is found, the question of replacing it is decided by the prescribing doctor; you cannot cancel the treatment yourself. The basis of prevention remains protection from ultraviolet radiation: avoid the sun in the middle of the day, wear closed clothing and a hat, use products with a high protection factor and renew them every two hours and after swimming.
- Stop sun exposure, cool compresses
- External anti-inflammatory agents as prescribed by a doctor
- Antihistamines for severe itching
- Replacement of the provoking drug - only through a doctor
- Long sleeves, wide-brimmed hat, glasses
- High factor sunscreens with regular renewal
- Do not apply perfume or essential oils before going out into the sun