Some people cannot tolerate sunlight - their skin sooner or later develops symptoms such as an itchy rash, hives, or blisters when exposed to sunlight. This is often referred to as a sun allergy .
However, the symptoms are not caused by an allergy. In most cases, they are caused by the skin condition polymorphous light eruption (PMLE) .
This condition generally first appears in affected individuals every year at the beginning of spring, when the sun shines for longer again and its rays become stronger.
This article discusses sun allergies, related conditions such as phototoxic reactions, possible causes, and ways to prevent and treat them. With one mouse click, you can select the section you would like to read and jump directly to it.
Contents
- What symptoms are typical of a “sun allergy”?
- What causes polymorphous light eruption?
- What are phototoxic and photoallergic reactions?
- How can you protect yourself if you have a sun allergy?
- Can PMLE be cured?
What symptoms are typical of a “sun allergy”?
In most affected individuals, symptoms of a sun allergy first appear in spring on areas of skin that have not been exposed to sunlight for a long time. The effects are therefore mainly seen on the arms and legs, as well as on the torso or décolleté.
In people with more pronounced polymorphous light eruption, increasingly intense sunlight also causes reactions on the face. Only in very severe cases of PMLE do affected individuals also experience skin reactions in winter. In general, the condition occurs more frequently in people with fair skin . It should also be noted that symptoms usually begin only one or two days after the skin’s first exposure to sunlight.
Typical symptoms of PMLE include skin redness, rash, and small blisters. The affected areas often cause severe itching. In severe cases, pustules and bleeding areas may even develop - scratching the itchy areas should be avoided at all costs.
If noticeable warmth of the affected areas accompanies the symptoms, this also indicates a sun allergy. If reddened blisters develop that look similar to hives caused by stinging nettles, solar urticaria may be present. This is a rare form of sun allergy that can also affect the circulatory system.
If circulatory problems such as dizziness, nausea, or weakness occur together with the symptoms, medical help should be sought immediately. A sun allergy is generally more bothersome than dangerous, and severe cases are rare.
However, spending time in the sun can also pose other risks, such as sunburn or heatstroke caused by overheating. If sun-allergy symptoms occur at the same time as sunburn, they may go unnoticed.
Very severe sunburn is often accompanied by overheating of the body, which can lead to heat collapse. Fortunately, polymorphous light eruption itself does not cause such problems.
What causes polymorphous light eruption?
Human skin has a mechanism that responds to increasing or more intense exposure to UV light. It produces increased amounts of melanin - a pigment that darkens the skin and blocks UV light. Melanin is why the skin tans after sunbathing.
In polymorphous light eruption, this process appears to be disrupted. It is therefore not surprising that sun allergies mainly affect people with fair skin types. Their skin stores less melanin than darker skin types and is also more susceptible to sunburn. It is a well-known phenomenon that many pale-skinned people do not tan, or tan only with difficulty, in summer.
Exactly how PMLE develops is still unclear - in addition to its connection with melanin, several other theories are circulating. One theory is that UV light stimulates the production of free radicals in the skin cells of people with “sun allergies.”
These are thought to trigger an overreaction of the skin’s immune system. Another theory suggests that exposure to sunlight can cause allergens to form, triggering PMLE like a classic allergy. None of these theories has yet been proven.
What is Mallorca acne?
The so-called “Mallorca acne” (acne aestivalis) was a skin condition that was particularly widespread among holidaymakers in sunny travel destinations during the 1980s. At that time, Mallorca was becoming a favorite island among Germans and recorded an especially high number of cases - hence the name. The symptoms resemble a sun allergy and can progress to the formation of acne-like pustules.
Today, however, this condition is hardly seen anymore, because it turned out that acne aestivalis occurred only in connection with certain sunscreens and in combination with UV radiation. The responsible ingredients were identified and are no longer included in modern products. Whether Mallorca acne was actually an immune reaction or “merely” skin irritation remains unclear.
What are phototoxic and photoallergic reactions?
Photoreactions can occur in connection with various substances. Some perfumes, for example, may contain ingredients that change when they come into contact with sunlight and develop toxic or skin-damaging properties. In addition, a number of different plant species are considered “phototoxic” and cause symptoms similar to those of a sun allergy.
Phototoxic reactions occur when biological or chemical substances “poison” skin cells in combination with UV exposure. Various medications can increase the skin’s sensitivity to light. Both topical medications (creams, ointments, etc.) and oral preparations (some antirheumatic drugs, diuretics, etc.) may have these properties.
If known, this is listed among the medication’s side effects. Anyone taking such a medication must avoid UV light, as otherwise skin irritation or even skin damage can occur very quickly. The risk of getting sunburned increases dramatically.
Phototoxic reactions are also often caused by plants whose sap contains phototoxic furocoumarins. These substances are found, among other things, in the peel of citrus fruits .
Another prominent example is St. John’s wort, which contains high concentrations of hypericin. Hypericin is used as an active ingredient, for example, in antidepressants. However, it increases the skin’s sensitivity to UV light, because phototoxic substances become poisonous only when they come into contact with UV light.
Gardeners and landscapers come into contact with phototoxic plants particularly often. However, symptoms sometimes also appear after a walk through flowering meadows wearing shorts.
The resulting skin problems are commonly referred to as “meadow grass dermatitis” , as they are triggered by various garden or wild plants. Well-known phototoxic plants include bishop’s weed, spotted hemlock, herbs such as anise, dill, fennel, or coriander, and umbellifers such as giant hogweed.
Photoallergic reactions are triggered by the interaction of UV light with chemical or other substances. Some medications, perfumes, or cosmetics can provoke immune-system overreactions in affected individuals. Mallorca acne may have been a photoallergic reaction.
How can you protect yourself if you have a sun allergy?
The simplest way to prevent a sun allergy is to avoid sunlight. This does not mean that people with PMLE can no longer leave the house. Unless you suffer from a severe form, you can protect yourself effectively with long clothing and sun hats to expose as little skin as possible to the sun.
Combine your choice of clothing with a high-quality sunscreen. It is advisable to choose a cream with the highest possible sun protection factor and a combination of UVA and UVB filters.
Anyone who is sensitive to heat and has light-sensitive skin should gradually acclimate themselves to the sun and heat. Initially, expose yourself to the sun for only a few minutes a day. In many cases, sun-allergy symptoms subside once the skin has become accustomed to UV light. Sunlight is strongest around midday - preferably go outside in the morning or toward evening.
It is sometimes claimed that dietary supplements containing antioxidants such as vitamin E or beta-carotene make the skin less sensitive to UV light. However, this is only a theory - their effectiveness against sun allergies has not been scientifically proven.
If you suffer from a severe form of polymorphous light eruption, you should definitely seek medical help.
Can PMLE be cured?
Polymorphous light eruption can be treated - but it cannot be completely cured. Nevertheless, even in many severe cases that prevent natural acclimatization to sunlight, a form of hyposensitization can be carried out under medical supervision.
Contact a dermatology practice near you for this. Targeted phototherapy can be performed there to gradually and gently acclimatize the skin to UV radiation. If a severe sun allergy is known, this treatment can begin during the winter months to prepare the skin for spring and summer.
Itching, rashes, and blistering can be treated with cooling and soothing ointments. In severe cases, corticosteroid medications can provide relief. However, treatment and management of a sun allergy should be aimed at preventing an acute outbreak from occurring in the first place.
