Brief overview
- What is sun allergy? Mostly not a real allergy, but another kind of hypersensitivity to UV radiation.
- Causes: not conclusively clarified; allergens or also free radicals (aggressive oxygen compounds) are suspected
- Symptoms: variable: itching, reddening of the skin, vesicles and/or blisters are common
- Diagnosis: patient interview, light test
- Treatment: cool, moisturize, in severe cases possibly medication or acclimatization by prior irradiation by the physician
- Prognosis: Over time, the skin gets used to the sun, so that the symptoms gradually decrease. However, those affected will never completely get rid of a sun allergy.
Sun allergy: Description
Typical symptoms of sun allergy such as itching and redness of the skin are similar to the symptoms of “real” allergies (such as nickel allergy). Actually, however, a sun allergy is usually not a classic allergy, i.e. an overreaction of the immune system (exception: photoallergic reaction). Instead, the body of the affected person can no longer protect itself sufficiently from the sun’s rays.
With a share of over 90 percent, polymorphous light dermatosis (PLD) is by far the most common form of sun allergy. In Western Europe, about 10 to 20 percent of the population suffer from it. Young, fair-skinned women are particularly affected. Many children also suffer from PLD.
Sun allergy in children
Some children also suffer from sun allergy. Toddlers and babies should generally be creamed with a high sun protection factor before being exposed to the sun. At this age, the body’s own protective mechanism against UV radiation is not yet fully developed. As a result, the little ones get sunburn or sun allergy more quickly.
The latter is most common on the face. The so-called “sun terraces” such as the nose, forehead and chin are particularly affected. In adults, these areas are often already accustomed to sun exposure, but not in children. Therefore, a head covering is advisable (also for adults) – especially since it not only protects against sun allergy, but also against sunstroke.
Sun allergy: symptoms
The type and severity of the symptoms of a sun allergy vary. Sometimes the symptoms are also delayed, so that it is not so easy for lay people to identify the sun as the “culprit”.
Polymorphous light dermatosis: symptoms
Polymorphous light dermatosis occurs mainly in the months of March to June. Mostly it appears on those parts of the body that are not used to the sun (décolleté, shoulders, neck, extensor sides of the arms and legs). The symptoms can vary greatly from person to person (hence the name polymorph = multifaceted). In addition, they often appear with a delay. Only hours or days after exposure to the sun does this sun allergy trigger symptoms:
- The skin begins to itch and burn.
- Reddish spots appear on the skin.
- Blisters, nodules or even blisters develop.
- The affected skin area may swell.
Other forms of sun allergy: symptoms
In addition to polymorphous light dermatosis, there are other types of sun allergy that manifest themselves somewhat differently. These include:
Phototoxic reaction.
In this case, chemical substances – known as photosensitizers – make the skin more sensitive to light. Sun allergy symptoms such as itching as well as an increased tendency to sunburn are the consequences.
Photoallergic reaction
This rare form of sun allergy is a true light allergy (photoallergy). The immune system forms antibodies, i.e. defense substances, which are directed against a certain substance such as a drug (e.g. antibiotics), cosmetics, make-up or a perfume. The next time the substance comes into contact with sunlight, the antibodies attack it – an allergic reaction occurs. The symptoms of photoallergy are similar to those of phototoxic reaction. It is therefore often difficult to distinguish between the different forms of sun allergy.
Majorca acne (Acne aestivalis).
This form of sun allergy is also called summer acne. It is considered a special form of polymorphous light dermatosis.
Signs of Mallorca acne are pinhead-sized nodules and skin patches that itch violently. The nodules resemble acne pustules. In fact, this form of sun allergy is especially common in people who tend to have acne or oily skin.
Light urticaria (urticaria solaris)
Treatment: Sun allergy – what to do?
If you develop symptoms of sun allergy, you should stay away from sunlight as much as possible. If this is not possible, then you should apply a sunscreen with a sufficiently high sun protection factor (SPF) and additionally cover the skin with clothing as much as possible (long pants, long sleeves, hat).
In the case of photoallergic as well as phototoxic reactions, you must also avoid the triggering substance.
The symptoms of a sun allergy can be relieved with dairy products (e.g. a curd pack) and – in severe cases – with medication:
Sun allergy treatment with dairy products
If the skin has been exposed to excessive sun and reacts with a sun allergy, you should cool and moisturize it. Cooling compresses with buttermilk, cottage cheese or yogurt from the refrigerator do just that. The coolness causes the blood vessels to contract and any swelling to subside. The moisture helps the damaged skin to recover.
Medicinal therapy for sun allergy
If general symptoms such as nausea and drop in blood pressure occur with light urticaria, you should immediately notify a doctor!
Sun allergy: Preventive treatment
Sun allergy patients can do a few things to prevent itching, blistering & co. from occurring in the first place:
Use sufficient sunscreen
The most important thing is to always make sure you have sufficient sun protection. Of course, this also applies if you do not have a sun allergy! UV rays increase the risk of skin cancer. Use a good sunscreen that offers at least sun protection factor (SPF) 30. In addition, the product should be as free as possible from preservatives and dyes.
Apply the sunscreen about 30 to 45 minutes before you go out in the sun. Then it has enough time to take effect. How long the protection lasts can be estimated using the following formula: Self-protection factor (about 5-45 minutes, depending on skin type) x SPF = minutes protected in the sun.
With a sun protection factor (SPF) of 30 and a fair skin type, this would mean: 10 minutes x 30 = 300 minutes. To be on the safe side, however, you should only actually spend 60 percent of this calculated amount of time in the sun. By the way: If you sweat a lot or go swimming in between, you should reapply your sunscreen.
Wear clothes
Clothing also protects against the sun’s rays, especially if it is made of a material that does not transmit much light. Hats, scarves and blouses, for example, can partially block UV rays from the skin even on the beach. Manufacturers specify a UV protection factor for some textiles, such as sportswear.
Stay indoors
At noon, the radiation is most intense, which is why you should rather stay indoors then. Window panes usually block most of the harmful rays. Patients with sun allergies should possibly still apply protective films.
Phototherapy
In cases of very severe sun allergy (e.g. severe polymorphous light dermatosis), phototherapy may be useful. In spring or some time before a planned vacation trip to the south, the skin is slowly accustomed to the sun’s rays. For this purpose, it is irradiated with increasing doses of UV light in several sessions. Possibly an active substance is applied beforehand, which makes the skin more sensitive to light. This is called photochemotherapy or PUVA (psoralen-UV-A phototherapy).
You must never perform phototherapy on your own – mistakes can cause extensive skin burns! Leave it to a dermatologist to perform.
Catch free radicals
Smokers should not take beta-carotene, as it can increase the risk of lung cancer – which is already increased by the nictoin anyway.
Get help
A sun allergy can interfere with social life. Some sufferers suffer so much that they develop a depressive mood. In that case, a doctor should be consulted. If necessary, professional psychotherapeutic support is advisable.
Sun allergy: causes and risk factors
Polymorphous light dermatosis
In polymorphous light dermatosis (PLD), the skin’s protective mechanism against UV rays does not function properly: when sun rays hit the skin, the body normally reacts by producing more melanin. This is a skin pigment that is supposed to protect the genetic material from the damaging UV rays. The skin turns brown due to the melanin. People from southern countries, where the sun shines a lot, therefore generally have a darker skin color. The more often a body is exposed to the sun, the more it normally gets used to the harmful rays.
Some scientists believe that allergens are formed in the body by the sun’s rays. Allergens are substances that activate the immune system so that it fights the supposedly harmful substance – as in a conventional allergy. However, this explanation has not yet been proven.
According to another theory, aggressive oxygen compounds (free radicals) form in the skin when exposed to sunlight, which are believed to be the cause of sun allergy. They can damage cells and increase the risk of skin cancer. The damage to skin cells by free radicals could also activate the immune system – resulting in symptoms of polymorphous light dermatosis. However, this assumption has also not yet been clearly proven.
Phototoxic reaction
The phototoxic reaction is triggered by the interaction between UV-A light, human cells and a chemical substance. The latter can be, for example, a drug substance, certain ingredients of perfumes or cosmetics or plant substances (furanocoumarins).
Photoallergic reaction
Mallorca acne
Majorca acne is caused by the interaction of UV-A rays with components of fatty sunscreen or the body’s own sebum in the uppermost layers of the skin. It has not yet been definitively determined whether the immune system is involved.
Photurticaria
The exact cause of light urticaria is unclear. However, it is known that the symptoms are triggered by the UV-A component in sunlight.
Sun allergy: examinations and diagnosis
If a sun allergy is suspected, the doctor will first discuss your medical history with you (anamnesis). In doing so, he will inquire about, for example
- the nature and course of the symptoms,
- any medication you may be taking, and
- possible previous illnesses.
In the vast majority of cases, the sun allergy is a polymorphous light dermatosis. More rarely, another form of sun allergy is behind it. To confirm the diagnosis, the doctor can perform a light test in which he irradiates certain areas of the skin with ultraviolet light. In polymorphous light dermatosis, the typical symptoms appear after a few hours on the treated areas.
In the case of sun allergy in combination with chemical substances such as phototoxic reaction, the doctor can apply suspicious triggers (such as ingredients of cosmetics) to suitable skin areas and then irradiate them. This photo patch test can be used to find out which substance is causing the skin symptoms in combination with UV light.
Sun allergy: course of the disease and prognosis
Unfortunately, sun allergy cannot be cured. People who are hypersensitive to sunlight are accompanied by this problem throughout their lives. However, the symptoms may diminish over time as the skin becomes accustomed to the sun.
The extent to which those affected suffer from the symptoms varies from person to person and depends above all on the form of the light allergy. However, through correct behavior, preventive measures and various therapy concepts, severe outbreaks can usually be prevented and the symptoms of a sun allergy can be significantly alleviated.
