UV Radiation / Damage

In the case of UVA radiation, a distinction has to be made between acute and chronic reactions. The acute (immediate) effects of UVA radiation can be, for example, the triggering of photodermatosis, also known as sun allergies or, medically, as polymorphic light eruptions (PLE). These reactions also include “Mallorca acne”. Certain medications, food additives, plants and plant-based medications can trigger phototoxic and photoallergic reactions of the skin.

Chronic (long-term) damage caused by UVA radiation includes the destruction of the elastic and collagen fibres, with premature ageing of the skin. Through excessive sunbathing over many years, exposure to UVA radiation also promotes the formation of skin cancer. The commonest forms of malignant tumours of the epidermis are basal cell (basal-cell carcinomas), squamous cell carcinomas, and malignant melanomas (“black skin cancer”).

The occurrence of malignant melanomas is related to the number of sunburns, basalomas and epitheliomas to the total exposure to sunlight. This is why melanomas develop in particular in areas of the skin that for most of the year are covered by clothing. Basalomas and epitheliomas, on the other hand, tend to occur in areas that are regularly exposed to the sun, e.g. the face, forearms, back, and backs of the hands. About

10 % of skin cancers are melanomas, and about 35 % basal cell carcinomas.

With moderate UV exposure, the body is able to repair the damage caused by the sun within 24 hours. However, as the number of sunburns increases, the ability of the body’s enzymes to repair the damage decreases. The result is ageing of the skin, wrinkling, and an increased risk of skin cancer.


Sunburn is an acute inflammatory reaction of the skin caused by overexposure to sunlight. The symptoms are redness and swelling of the skin and a burning sensation, and in more severe cases also blistering and possibly even fever. Sunburn is caused by the UVB radiation. This triggers the formation of so-called free radicals in the skin, which result in inflammation. Prostaglandins (i.e. hormones and messenger substances of the tissue) are also involved in the inflammation reaction. UVB radiation induces a delayed skin reaction, with the result that the symptoms only make themselves felt some 6 to 24 hours later. The healing process after sunburn is accompanied by scaling and pigmentation of the skin. Sunburn reduces the natural protective functions of the skin, making it more easy for germs and chemical substances to penetrate. Sunburn also places an excessive burden on the immune system of the skin.

Polymorphic light eruption (PLE, sun allergy)

Polymorphic light eruption is the commonest form of sun allergy. A specific allergen that causes this skin reaction is not yet known. However, because of the similarity of this reaction with photo-allergic contact dermatitis, it is assumed that an as yet unknown substance in the skin is changed by light and that the skin responds allergically to this substance. The symptoms are severe itching, redness, blistering, nodulation and swelling of the skin. These symptoms mostly occur in untanned skin, especially in spring. Sun allergies predominantly affect women. It is estimated that about 20 % of the population suffer from sun allergies. In many cases, the face and hands do not show any symptoms as they are exposed to UV radiation throughout the year. In the case of 60% of patients, the polymorphic light eruption is triggered by UVA light.

To prevent it PLE from occurring, the following measures are recommended:

  1. Gradual acclimatisation to sunlight by slowly increasing exposure to UVA radiation over a period of 4 weeks (3-4 sessions a week).
  2. Taking beta-carotin (not very effective).
  3. Taking anti-histamine medication already 3 days before going away on holiday and during the whole holiday (moderately effective).
  4. Taking anti-malaria drugs (hydroxychloroquin) one day before and every day while sunbathing.
  5. Using sunscreens with maximum sun protection factor in the UVA and UVB range. The sunscreen must guarantee protection against UVA radiation (“Australian standard”).

The best recommendations are to gradually acclimatise the skin to exposure to sunlight and to use sunscreens with high sun protection factors for UVA and UVB.

Mallorca acne (acne aestevalis)

“Mallorca acne” particularly tends to affect women with a greasier type of skin. Under exposure to UVA radiation, small, itching blisters (papules) form at the hair follicles in the area of the front and back of the neck, the decolleté and the arms. This illness hardly ever occurs in the countries of northern Europe, but only when people go on holiday in the south. It is believed to be caused by free radicals (i.e. molecules that damage the cells), which are mainly produced under UVA exposure. The radicals cause the oxidation of greases and emulsifiers in skin care products and sun creams. The result are lipoperoxides, which trigger an inflammatory reaction especially in the area of the hair follicles. The result are acne-like skin symptoms.

The best means of prevention is to use sunscreen and after-sun products that contain no grease or emulsifiers. Sunscreens in gel form can be a useful alternative.

Photo-allergic and photo-toxic reactions

Photo-allergic reactions only occur in people with an individual immunological disposition, so are relatively uncommon, whereas photo-toxic reactions can occur in anybody. Medications more frequently trigger photo-toxic reactions than photo-allergic ones. Contact with the photo-active substances can occur in many different ways, e.g. through taking medication or using cosmetics or in the course of activities in industry and farming, and even working in the garden at home. Clinically, photo-allergic reactions are characterised by blistering, scaling and redness, and subjectively by itching. Photo-toxic reactions, on the other hand, show all the symptoms of excessive sunburn, with itching, burning and a prickly feeling of the skin.

Light allergies caused by medication are generally on the increase. Before going in the sun, people taking medication are advised to read the drug information sheet to see whether photo-sensitisation is listed as a possible side-effect.

Grass dermatitis (phytophotodermatitis)

Contact between sweaty skin with plants and grasses before and during exposure to sunlight can cause severe redness of the skin, with blistering. This may result in brown hyperpigmentations of the skin, frequently in the bizarre shape of the leaf or blade of grass, which can persist for months or even years. The cause of this reaction are photo-active substances of the plants such as psoralenes (furocumarines) which reinforce the effect of sunlight on the skin. Plants of this kind include a number of grasses, herbs such as parsley, celery, yarrow, wild carrot and giant cow parsnip, as well as lemons and figs. Also perfumes containing ingredients such as bergamot, lemon. lavender, lime, sandalwood and cedar oil can trigger hypersensitivity reactions to sunlight.

Photo-allergic reactions

These are triggered by a cell-transmitted immune response of delayed type (type IV). However, it has not yet been possible to identify the allergens induced by UV light. They only form on repeated exposure to sunlight and after medication has been taken. They are mostly caused by UVA light, less frequently by visible light and long-wave UVB light.

Photo-toxic reactions

These reactions occur in correspondingly sensitised people on first contact with sunlight after taking medication. They are usually caused by UVA light.

Once the person stops taking the medication that causes the reaction, photo-allergic and photo-toxic reactions gradually disappear over a period of weeks or months. In many cases, a hyperpigmentation (brown discolouring) of the skin may persist for some time.

There are many medications that can trigger photo-allergic and photo-toxic reactions. These include antibiotics, antidepressants, antidiabetics, antihystamines, antihypertensives, antiparasitics, cytostatics, diuretics, non-steroid antirheumatics, and psychopharmaceuticals. It would take too much space to list all these drugs in detail. People taking medication are recommended to consult their physician and also to read the drug information sheet about the possibilities of photosensitisation. Sunscreens, contraceptive pills and artificial sweeteners (saccharine, cyclamate) can also cause photosensitivity.

People should inspect their own skin from head to toe once a month in summer to detect any changes in their moles (pigmented naevi). If any new moles suddenly appear or if existing ones grow irregularly in shape, change colour, become inflamed or bleed, these are suspicions signs and should be examined by a doctor.

The following clinical ABCDE rule can be useful for the early detection of suspicious moles (melanomas):


Asymmetry of the mole

= Asymmetry of the mole


Borders (irregular)

= Borders (irregular)


Colour (irregular, spreckled, lighter or darker)

= Colour (irregular, spreckled, lighter or darker)



= Diameter exceeding 5 mm (approx. the size of an eraser on the end of a pencil)



= Elevation (knotty structure of irregular height) and / or enlargement

If any of these 4 criteria apply, the mole (pigment naevus) should be removed. In the case of any uncertainty, be sure to consult a dermatologistskinpilot side tour.