Some people cannot tolerate sunlight — sooner or later, their skin 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 polymorphic light eruption (PLE) .
For people affected, this condition usually first occurs each year at the beginning of spring, when the sun shines for longer and its rays become more intense.
This article discusses sun allergy, related conditions such as phototoxic reactions, possible causes, and ways to protect against and treat them. Click on a section to read it and jump straight to it.
Contents
- What symptoms are typical of “sun allergy”?
- What causes polymorphous light eruption?
- What are phototoxic and photoallergic reactions?
- How do you protect yourself if you have a sun allergy?
- Can PLD be cured?
What symptoms are typical of “sun allergy”?
For most people affected, symptoms of 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 most noticeable on the arms and legs, as well as on the torso and décolletage.
In people with more severe polymorphic light eruption, increasingly intense sunlight also triggers reactions on the face. Only in very severe cases of polymorphic light eruption do affected people experience skin reactions in winter as well. In general, the condition is more common in people with fair skin . It should also be noted that symptoms usually start one to two days after the skin is first exposed to sunlight.
Typical symptoms of PLD include skin redness, rash, and small blisters. The affected areas often cause severe itching. In severe cases, pustules and bleeding areas may even develop – it is essential to avoid scratching the itchy areas.
Noticeable warmth in the affected areas of skin alongside the symptoms also points to sun allergy. If red blisters develop that look similar to the welts caused by stinging nettles, it may be solar urticaria . This is a rare form of sun allergy that can also affect the circulation.
If symptoms occur along with circulatory problems such as dizziness, nausea, or weakness, seek medical help immediately. Sun allergy itself is more of a nuisance than a danger, and severe cases are rare.
However, other dangers can also arise from spending time in the sun, such as sunburn or heatstroke caused by overheating. If the symptoms of sun allergy occur at the same time as sunburn, they could 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 allows it to respond to increased 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 seems to be disrupted. It is therefore no surprise that people with fair skin are particularly prone to sun allergy. Their skin stores less melanin than darker skin and is also more sensitive to sunburn. It is well known that many fair-skinned people do not tan, or only tan with difficulty, in summer.
Exactly how PLD develops is still unclear - in addition to its connection with melanin, several other theories are circulating. One suggestion is that UV light stimulates the production of free radicals in the skin cells of “sun-allergic” people.
These are thought to cause an overreaction of the skin’s immune system. Another theory suggests that allergens can form under exposure to sunlight, triggering PLD like a classic allergy. Neither theory has been proven so far.
What is Mallorca acne?
So-called “Mallorca acne” (acne aestivalis) was a skin condition that was particularly prevalent among holidaymakers in sunny destinations in the 1980s. Mallorca was beginning to become a favorite island for Germans at the time and saw especially many cases - hence the name. The symptoms resemble a sun allergy and can include acne-like pustules.
Today, however, this condition is rare, as it turned out that acne aestivalis only occurred in connection with certain sunscreens and in interaction with UV radiation. The ingredients responsible were identified and are no longer found in modern products. It remains unclear whether Mallorca acne was actually an immune reaction or “just” skin irritation.
What are phototoxic and photoallergic reactions?
Photoreactions can occur in connection with various substances. Some perfumes, for example, may contain ingredients that change when exposed to sunlight and develop toxic or skin-damaging properties. In addition, there are several plant species that are considered “phototoxic” and cause symptoms similar to a sun allergy.
Phototoxic reactions occur when biological or chemical substances combine with UV exposure to “poison” skin cells. Various medications can therefore increase the skin’s sensitivity to light. Both topical medications (creams, ointments, etc.) and oral medications (some anti-inflammatory drugs, diuretics, etc.) can 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 damage can occur very quickly. This greatly increases the risk of sunburn.
Phototoxic reactions are also often caused by plants whose sap contains phototoxic furocoumarins. These substances are found, among other places, in the peels of citrus fruits .
Another prominent example is St. John’s wort, which contains high concentrations of hypericin. Hypericin is used as an active ingredient in antidepressants, for example. However, it increases the skin’s sensitivity to UV light, because phototoxic substances only become toxic when they come into contact with UV light.
Gardeners and landscapers are particularly likely to come into contact with phototoxic plants. But symptoms sometimes also appear after a walk through flowering meadows in shorts.
The resulting skin problems are colloquially called “meadow grass dermatitis” because 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 chemicals or other substances. Some medications, perfumes, or cosmetics can provoke an overreaction of the immune system in affected individuals. Mallorca acne may have been a photoallergic reaction.
How do you protect yourself if you have a sun allergy?
The easiest way to prevent a sun allergy is to avoid sunlight. This doesn’t mean that you can no longer leave the house if you have PLD. Unless you have a severe case, you can protect yourself effectively with long clothing and sun hats to expose as little skin as possible to the sun.
Pair your clothing choices with a high-quality sunscreen. It is recommended 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 acclimatize to the sun and heat. At first, expose yourself to the sun for only a few minutes a day. In many cases, sun allergy symptoms subside once the skin has acclimatized to UV light. The sun is strongest around midday, so go outside in the morning or toward evening instead.
It is sometimes said 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—there is no scientific evidence that they are effective against sun allergy.
If you suffer from a severe form of polymorphous light eruption, you should definitely seek medical help.
Can PLD be cured?
Polymorphous light eruption can be treated — but it cannot be cured completely. Nevertheless, even in many severe cases that prevent the skin from naturally acclimatizing to sunlight, a form of desensitization can be carried out under medical supervision.
To do this, contact a dermatology clinic near you. There, targeted phototherapy can be used to gradually and gently acclimatize your skin to UV radiation. If you are known to have a severe sun allergy, this treatment can begin during the winter months to prepare your skin for spring and summer.
Itching, rashes, and blisters can be treated with cooling and soothing ointments. In severe cases, medications containing cortisone can provide relief. However, treatment and management of sun allergy should aim to prevent an acute flare-up from occurring in the first place.
