bubble_chart Overview

Solar dermatitis, also known as sunburn, is a phototoxic reaction caused by excessive exposure to medium-wave ultraviolet radiation from sunlight, leading to localized skin inflammation in humans.

bubble_chart Etiology

Sunlight is mostly composed of visible light, with a spectral range of approximately 390 to 770 nm. In addition to stimulating the retina of the eye, it also possesses certain biological activities. Wavelengths above 770 nm are infrared rays, which are invisible heat rays that can cause the skin to redden. Ultraviolet light falls below 390 nm. The condition is caused by medium-wave ultraviolet light in the range of 290 to 320 nm. The skin's reaction varies depending on the duration of exposure, range, environmental factors, and skin tone. Heat can increase the body's sensitivity to ultraviolet light. The onset of this condition is also related to individual susceptibility. It is more common in late spring and early summer. Residents of high-altitude areas, those engaged in snowfield exploration, or individuals working on water surfaces are more prone to developing this condition.

bubble_chart Pathological Changes

There are individual necrotic keratinocytes in the epidermis to large areas of confluent necrosis. The superficial dermal blood vessels are dilated, with a small amount of perivascular lymphocyte infiltration.

bubble_chart Clinical Manifestations

When the skin is exposed to intense sunlight for several hours to more than ten hours, a rash may develop on exposed areas such as the face, neck, and back of the hands. Based on the severity of the skin reaction, it is classified into grade I sunburn and grade II sunburn.

Grade I sunburn manifests as diffuse erythema on the localized skin after sun exposure, with clearly defined borders, peaking within 24 to 36 hours.

Grade II sunburn is characterized by localized skin redness and swelling, followed by the formation of blisters or even large bullae, with tense blister walls and pale yellow fluid. Symptoms include a burning pain or prickly itch. After the blisters rupture, they leave erosions, which soon dry and form scabs, resulting in either hyperpigmentation or hypopigmentation.

The condition peaks on the second day after sun exposure and may be accompanied by systemic symptoms such as fever, headache, palpitation, lack of strength, nausea, and vomiting. Recovery typically occurs within a week.

bubble_chart Diagnosis

The diagnosis can be based on a history of sun exposure, redness and swelling or blisters on exposed skin, a strong correlation with the season, and a subjective sensation of burning and stabbing pain.

bubble_chart Treatment Measures

1. Local Treatment

(1) Apply 2.5% indomethacin solution (pure vinyl alcohol, propylene glycol, dimethylacetamide, ratio 19:19:12) externally.

(2) For large blisters or excessive exudate, use 2–4% boric acid solution; milk solution (milk and water 50:5) or saline solution (one teaspoon of salt dissolved in 500–600ml of water) for wet compresses, 15–20 minutes each time, 2–3 times a day until the blisters dry. Most blisters do not require treatment.

2. Systemic Treatment

(1) Antihistamines: For pruritic sunburn. Cyproheptadine 2mg orally three times daily; Chlorpheniramine 4–8mg orally three times daily; Astemizole 10mg orally once daily.

(2) Analgesics: Aspirin 1g orally three times daily; Paracetamol 0.25–0.5g orally 3–4 times daily.

(3) Corticosteroids: For severe sunburn, Prednisone 10mg orally three times daily for 2–3 days, but must be administered within 36 hours or sooner after sunburn to reduce redness, swelling, heat, and pain.

3. Traditional Chinese Medicine Treatment Traditional Chinese Medicine refers to sunburn as "sunburn sore." The treatment principle focuses on cooling blood and clearing heat, as well as removing dampness and dispelling wind. The formula can be modified from Cooling Blood Wind-Dispersing Powder.

bubble_chart Prevention

Regular outdoor exercise can stimulate melanin production in the skin. For patients with heightened sensitivity to sunlight, it is advisable to avoid prolonged sun exposure. Protective measures such as using umbrellas, wearing straw hats, and gloves should be taken when going outside. Additionally, some photoprotective agents can be applied externally, such as reflective sunscreens: 15% zinc oxide ointment, 5% titanium dioxide emulsion, 5% para-aminobenzoic acid (PABA) emulsion or tincture, or 10% salol ointment. These should be applied to exposed skin areas 15 minutes before sun exposure.

bubble_chart Differentiation

This disease needs to be differentiated from contact dermatitis and niacin deficiency. Contact dermatitis: There is a history of exposure to irritants, unrelated to sun exposure. It can occur in any season, with rashes appearing at the contact site and accompanied by pain and itching. Niacin deficiency: In addition to sun exposure, rashes also appear on non-exposed areas, often accompanied by symptoms of the nervous and digestive systems.