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Polymorphe Lichtdermatose
Not the sun itself but the sudden change overwhelms the skin — slow habituation helps.
Also known as: polymorphic light eruption · PLE · sun allergy
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
“Sun allergy” is usually polymorphic light eruption — an overreaction of the skin to unaccustomed UV radiation. Typically it appears in spring or the first days of a holiday, when the skin gets a lot of sun again for the first time: hours to a day or two later, itchy redness, small blisters or bumps appear on the exposed areas — décolleté, arms, backs of the hands. It is unpleasant but harmless and settles on its own. A welcome “hardening effect” occurs: over the summer, as the skin gradually gets used to the sun, the symptoms often become less frequent. Prevention through easing into the sun and good sun protection helps most. An important distinction: if the skin suddenly reacts strongly and newly, a medication or cosmetic may have made it light-sensitive (a phototoxic reaction); with marked or atypical rashes, a visit to the dermatologist is worthwhile.
Sunburn is red across an area and burns; the light reaction itches and shows blisters or bumps on the places uncovered first. Sunburn reaches its peak only the next day.
Get the skin used to it gently — short times, build up; avoid midday sun at first.
High SPF (also UVA), clothing and a hat protect best.
Cooling and anti-itch remedies help; keep the affected skin out of the sun.
With strong, widespread, atypical or recurring reactions.
Cortisone cream and antihistamines ease the rash once it is there; they do not prevent it. What prevents it is getting used to light: slowly rising doses over two to four weeks before the season, either in a practice or through gradual sun. Sunscreen with high UVA protection is decisive, because UVA is the trigger and ordinary window glass lets it through. Calcium and beta-carotene preparations are used traditionally; the study base for them is small.
The rash appears hours to two days after the first stronger sun of the season and heals in seven to ten days if the skin is spared. About ten to twenty in a hundred people are affected in our latitudes, women more often, usually starting between twenty and thirty. It improves through the summer because the skin gets used to it — and that adaptation is exactly what preventive light treatment over two to four weeks uses.
The skin overreacts to the first strong sun in spring/holiday.
Itchy redness, blisters or bumps on sun-exposed areas, hours to days later.
Settles on its own; over summer the skin often becomes more tolerant.
Sudden strong new reaction → a drug/cosmetic may photosensitize; atypical rashes → see a doctor.
The most important distinction: a rash on sun-exposed areas together with joint pain, tiredness or fever can belong to an autoimmune illness and is treated quite differently.
Anyone who consistently avoids the sun more often has low values. That belongs replaced rather than putting more strain on the skin.
Skin and lining renew themselves quickly and need zinc for it. With places that heal badly, cracked corners of the mouth and frequent skin infections a lack is a serious possibility.
Without vitamin C no stable collagen forms — the wound closes but holds less well. With a very one-sided diet, smoking and alcohol the intake is often tighter than assumed.
Steers the horn-forming of the skin. Too little makes it rough and dry, too much over longer periods harms liver and bone — and in pregnancy a strict upper limit applies.
Every healing needs building material. Anyone eating little during an illness loses exactly that — a sufficient amount spread across the day belongs to the treatment.
Traditionally taken before the holiday, since the 1970s. The controlled studies on polymorphic light eruption found small differences at best — started, if at all, 8–10 weeks before the sun.
As nicotinamide — the form without flushing — 500 mg twice daily was studied: in people with a history of light-skin cancer the rate of new lesions fell. That is no proof for light allergy itself, but it is the same repair pathway.
Polymorphic light eruption mostly affects younger women, and many report a clustering in particular phases of the cycle. With the rare spring form a link with the pill has been described.
Anyone avoiding the sun regularly has low vitamin D levels. That is no reason to go into the sun — it is a reason to measure the value and cover it another way.
For beta-carotene the evidence is weak. Nicotinamide, 500 mg twice daily, showed protection against light damage in studies — started some weeks before the sunny season.
Anyone avoiding the sun makes less vitamin D — with sun allergy a deficiency is therefore more common. On the skin reaction itself it has no effect.