Acute skin damage

Acute skin damage due to UV radiation includes sunburn, sun allergy and phototoxic reactions.

Sunburn

Sunburn is an inflammation of the skin due to UV radiation. This inflammation manifests as reddening and swelling of the affected areas of skin, as well as blistering in particularly serious cases. The resulting discomfort reaches its peak within 12 to 36 hours.

The dose of UV radiation that leads to this reddening of the skin is called the "minimal erythema dose" (MED; unit: joules per square metre, J/m2). For example, the sensitive skin type II has a MED of 250 J/m2. Theoretically speaking, people with skin type II can reach this dose in about 20 minutes in Central Europe on a sunny day with a UV index (UVI) 8.

Frequent sunburn in childhood and adolescence increases the risk of developing skin cancer (malignant melanoma) by a factor of between two and three!

The UV index serves as an important guide for avoiding sunburn.

Sun allergy

"Sun allergy" is a colloquial term used to refer to various skin conditions induced by UV radiation.

The most common form of “sun allergy” is polymorphic light dermatosis. Following exposure to UV, in particular to UV-A, the skin develops patchy reddening, blisters and nodules (papules) with an intense itching sensation, typically affecting the neck, upper chest, upper arms, backs of the hands, or thighs.

So-called "Mallorca acne" is a special form of polymorphic light dermatosis whereby skin lesions are caused by the interaction of UV radiation and lipids from sunscreen (or the body’s own cutaneous sebum).

Phototoxic reactions

A series of substances that can be found in medications, herbal remedies and cosmetics may provoke phototoxic reactions of the skin, resulting in skin conditions ranging from reddening and burning pains to serious burns. These substances are said to have a photosensitising effect.

Photosensitising substances can also be found in certain plants and foodstuffs, such as:

• citrus fruits
• celery
• giant hogweed (Heracleum mantegazzianum).

If a person touches or eats these plants, subsequent exposure to UV radiation (from the sun or a solarium) can result in skin conditions of varying severity.

The interaction between UV radiation and photosensitising substances can trigger allergic skin reactions. Potential photosensitising effects of medications or herbal remedies should be discussed with a doctor or pharmacist.