Sun Allergy

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Sun Allergy
Sun Allergy

Video: Sun Allergy

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Video: Can You Be Allergic To Sunlight? 2023, January

Sun allergy

Sunlight provides warmth, lifts the mood and is also important for bone metabolism. However, excessive UV rays sometimes have unpleasant consequences, for example sunburn, premature skin aging or an increased risk of skin cancer. Reddening, itchy skin changes caused by sunlight and subsumed under the term “sun allergy” can also cloud the joy of sunshine…


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  • Advice, downloads & tools
  • Sun allergy: what is it?
  • Diagnostic tests
  • Photoallergic reactions
  • Phototoxic reactions
  • Polymorphic photodermatosis
  • "Summer acne" ("Mallorca acne")
  • ">Solar urticaria: rare, but to be taken seriously



Sun allergy: what is it?

The term “sun allergy” summarizes various skin diseases that have one thing in common: the trigger is sunlight - mostly UV-A light. This is not an allergic reaction in the “classic” sense, although processes in the immune system play an important role. In general, the development of these skin diseases has not yet been fully researched. The most common are photoallergic reactions, polymorphic light dermatosis (PLD) or “summer acne” (“Mallorca acne”). Even behind glass, you shouldn't feel like being in a false sense of security, because UV-A light penetrates it. Clothing with dense fabric protects well against UV-A rays. There are fabrics that contain extra UV protection. When using sunscreen, always make sure:that these protect against both UV-A and UV-B radiation.

Note The rashes should always be clarified with a dermatologist. This person makes the diagnosis and initiates therapy.

Diagnostic tests

The so-called photo patch test has proven itself in order to track down the triggering substances that, together with sunlight, cause the unpleasant skin symptoms. In this case, the suspected triggers are applied to the back - in two places each. After about 24 hours, one test site is exposed to UV-A light, the other is not. The next day the skin areas are compared with one another. If a skin reaction appears on the skin exposed to UV-A light, the culprit has been unmasked.

The so-called MED test determines the lowest radiation dose at which sunburn occurs in the UV-A range. Combined with a possible trigger (e.g. photosensitizing substance) or without it, the possible cause can be determined.

Photoallergic reactions

If the skin reacts to certain substances under the influence of sunlight with the overreaction of cells of the immune system, it is a photoallergic reaction. A distinction is made between two forms:

  • Photoallergic contact dermatitis: Triggers are cosmetics (including light filter substances such as oxybenzone, benzoophenone-4, Octyl Dimenthyl PABA), make-up or perfume.
  • Photoallergic drug reaction: Triggers are drugs (e.g. antibiotics).

Mainly areas of the skin that are directly exposed to the sun are affected. Gradually, however, the allergic reaction can also spread to other areas of the skin (“scattering”). A photoallergic reaction manifests itself as itchy and reddened skin - approx. One to three days after contact with the allergy trigger. In addition, blisters can form that are scratchy and wet. If the allergenic substance has been identified by means of an allergy test, it must be avoided. In principle, those affected should not take too long sunbathing and protect themselves with a high sun protection factor. Cortisone or other drugs as well as UV-A light radiation can also be used.

Note However, it should be noted that - even if the triggers are avoided - the formation of eczema from solar radiation can still occur.

Phototoxic reactions

Phototoxic reactions lead to direct interactions between UV-A light, human tissue and a chemical substance. In addition, the tendency to sunburn is increased. The symptoms are also similar to those of a sunburn: reddening, local pain, blistering and swelling. No special tendency is required for phototoxic reactions - these can be triggered in every person. A number of substances can have a photosensitizing effect via the skin, the bloodstream or even when absorbed in the digestive tract. A cascade is triggered, which leads to the appearance of tissue-damaging substances. The triggers include, for example, some medications (e.g. tetracycline antibiotics). These side effects are pointed out in the package insert for the relevant medicinal products.

If the contact with plants that contain so-called furocoumarins (e.g. angelica) leads to increased photosensitivity, it is meadow grass dermatitis. After contact with meadow grasses, streaks and dark and / or light discoloration appear on the respective skin areas. If darker streaks or spots appear on the skin in connection with the use of perfumes or perfume-containing cosmetics, this is called berloque dermatitis. Furocoumarins are also responsible for this.

Once diagnosed, avoiding the triggering substance and using cooling compresses and, if necessary, using cortisone may help. Disinfectant sprays are sometimes used for meadow grass dermatitis. In the case of berloque and meadow grass dermatitis, pigmentation disorders can be prevented by using hydroquinone in combination with hydrocortisone - peeling cures with vitamin A acid are also used.

Note If blisters appear on large areas of the skin, this requires immediate medical treatment.

Polymorphic photodermatosis

Polymorphic light dermatosis (PLD) is the most common form of so-called "sun allergies". This results in an abnormal reaction of the skin to sunlight - presumably due to UV-A rays from the sun. The exact causes of PLD are not yet fully understood. It manifests itself in itchy rashes on parts of the body that are particularly exposed to the sun (e.g. face, arms, décolleté). If the sun is avoided and clothing with the lowest possible light permeability is worn, an improvement usually occurs after a few days. Often the symptoms appear in spring and disappear in autumn. Improvement can be achieved through slow precautionary accustoming to the sun or treatment with UV light by the dermatologist and the use of sunscreens with UV-A protection.In severe cases, so-called photochemotherapy is used. The active ingredient 8-methosypsoralen and UV-A radiation are used for prophylaxis. In addition, the intake of beta-carotene, nicotinamide (in combination with folic acid) and the intake of omega-3 fatty acids from fish oil - after consulting your doctor - may be helpful.

"Summer acne" ("Mallorca acne")

A special form of polymorphic light dermatosis is the so-called "summer acne" - also known under the term "Mallorca acne". This causes a skin reaction that manifests itself as severe itching, nodules and acne-like pustules. "Summer acne" occurs a few days after the first sunbath of the year. The triggers are UV-A radiation in combination with components of fatty sunscreens or the body's own sebum in the top layers of the skin. The extent to which immunological processes play a role has not yet been finally clarified. People with oily or acne-prone skin are particularly affected. If there are signs of "summer acne", the sun must be avoided. As a preventive measure, it makes sense to use fat-free sun protection products (e.g. special gels) orUsing skin care products and slowly getting your skin used to the sun. The attending doctor may also prescribe antihistamines.

Solar urticaria: rare, but to be taken seriously

Solar urticaria is a rare skin reaction to exposure to sunlight. Here, too, the mechanism of origin has not yet been clarified - only the triggering UV-A radiation has already been proven. A few minutes after exposure to the sun, wheals form, which last only a few minutes to hours. However, general symptoms such as nausea or a drop in blood pressure (e.g. associated with dizziness) can occur if large areas of the skin are affected.

The most effective treatment measure for solar urticaria is avoiding solar radiation or effective sun protection. Treatments with UV light or by means of plasmapheresis (taking blood plasma) are successful in individual cases. Antihistamines and the active ingredient (hydroxy) chloroquine are also used.

Note If symptoms such as nausea or dizziness (e.g. associated with a drop in blood pressure) occur, medical help must be sought immediately or the ambulance notified.

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