What is Solar Urticaria?
Solar urticaria is a condition where a person develops an unhealthy sensitivity to sunlight. This leads to recurring bouts of hives or rash on the skin areas that have been exposed to sunlight. While it’s normally a harmless condition, it can greatly interfere with a person’s daily activities and significantly affect their quality of life.
What Causes Solar Urticaria?
Solar urticaria, or a skin reaction to sunlight, happens when the skin is exposed to certain types of light. The specific light that causes this reaction can range from ultraviolet B to visible light (light with a wavelength of 300 to 500 nanometers). This can vary from person to person.
Risk Factors and Frequency for Solar Urticaria
Solar urticaria is a rare type of skin condition, accounting for less than 0.5% of all skin rashes, and 7% of all skin conditions related to light. Though it can start at any age, it usually begins when people are in their mid-thirties, but in rare cases, it can affect newborns or older adults. It’s more common in females but it can affect anyone, regardless of their ethnicity.
- Solar urticaria is a rare type of skin condition caused by sunlight.
- It accounts for less than 0.5% of all skin rashes.
- This condition makes up 7% of all skin conditions caused by light.
- It normally starts in the mid-thirties but can affect any age group, including newborns and older adults.
- It’s more commonly found in women, but there’s no difference when it comes to ethnicity.
- In less than 30% of cases, there’s a history of atopy, which is a tendency to develop allergic conditions.
- Up to 16% of people with solar urticaria may also have other types of chronic skin rashes.
Signs and Symptoms of Solar Urticaria
Solar urticaria is a skin condition caused by sun exposure, typically resulting in redness and swollen spots on the skin within minutes of sunlight contact. This often affects areas of skin that are exposed to sunlight, but can also occur on areas of skin covered by thin, white clothing that lets sunrays through. Interestingly, skin that’s usually covered tends to react more strongly when it is finally exposed to the sun. The skin on the face and hands, on the other hand, seems more resistant to sun damage. The rash can cause itching or a burning sensation. Swelling around the eyes or other mucous membranes may also be observed. Some individuals may also notice a skin reaction when the skin is scratched.
This condition may sometimes be accompanied by general symptoms like feeling sick, breathing difficulties, fainting, especially if large portions of skin are exposed to sunlight for a long time. However, severe reactions like anaphylactic shock are rare in solar urticaria. It is worth noting that in most cases, about 75% of skin symptoms ease off within an hour of stopping sun exposure and completely within 24 hours. The severity and duration of the symptoms also depend on how intense the sunlight is.
- Redness and swollen spots on sun-exposed skin
- Itching or burning sensation with the rash
- Possibility of swelling around eyes and other mucous membranes
- General symptoms such as nausea, breathing difficulties or fainting if large areas of skin are exposed to sunlight
- Skin symptoms mostly resolve within an hour of stopping sun exposure, and completely within 24 hours
- Symptoms’ severity and duration depend on the intensity of sunlight
Testing for Solar Urticaria
If your skin breaks into hives a few minutes after being exposed to sunlight, this could be a sign of solar urticaria. When not exposed to sunlight, your skin would appear normal.
Solar urticaria can sometimes be mistaken for other skin conditions caused by light, such as polymorphous light eruption (different types of skin rashes that appear after sunlight exposure), lupus erythematosus (an autoimmune disease that can cause skin rashes), drug-induced photosensitivity (skin reactions caused by certain medications in response to sunlight), and photo contact dermatitis (skin inflammation caused by contact with certain substances followed by exposure to light). However, it’s important to note that solar urticaria can also coexist with these other conditions.
To confirm a diagnosis of solar urticaria, different types of lights, including UVA, UVB, and visible light, are used for testing. Natural light may also be used occasionally. The goal of this testing is to determine which type of light causes the hives and the minimal amount of light needed to trigger the reaction. This information helps with treatment, as it guides patients on what types of light they need to avoid.
During the test, different amounts of light are aimed at the patient’s back from 10 to 15 centimeters away. Doctors monitor the skin’s response every 10 minutes for an hour. If you have solar urticaria, hives and redness will appear right after the test and disappear a few minutes after the light is turned off. However, in some cases, hives might not appear with artificial light and can only be triggered by natural sunlight. If the initial test doesn’t bring out the hives, the test may have to be repeated.
In some cases, a skin sample may be taken to eliminate the possibility of other skin conditions caused by light. Skin affected by solar urticaria typically shows standard signs of hives, such as swollen skin cells and an influx of white blood cells called neutrophils, monocytes, and eosinophils.
In some cases, additional testing may be carried out to rule out skin reactions caused by certain substances or drugs when exposed to light.
Treatment Options for Solar Urticaria
Solar urticaria, or a form of skin rash brought on by exposure to sunlight, does not have a standard treatment protocol at the moment. A variety of treatments have been tried with mixed results. It is generally recommended that patients avoid too much sun exposure and protect their skin using broad-spectrum sunscreens and dark clothing to minimize their symptoms.
In many cases, doctors recommend medications generally used for chronic urticaria (a long-term hives condition) which are called second-generation antihistamines. Common examples are loratadine, fexofenadine, and cetirizine. These medications often relieve symptoms but may need to be used in higher doses than usual. However, they may not reduce redness in solar urticaria patients.
Interestingly, areas of the skin that are frequently exposed to the sun seem to build up a certain tolerance to sunlight. To take advantage of this, treatments like phototherapy (exposure to specific types of light) and photochemotherapy (a treatment that combines a drug and exposure to light) have been used to help the skin become more resistant, or “harden”, to sunlight. Photochemotherapy appears to have a longer-lasting effect than phototherapy alone.
For solar urticaria that is difficult to treat, other treatments such as intravenous immunoglobulins (proteins that help the body fight off diseases), plasma exchange (a procedure that filters the blood), cyclosporine, afamelanotide, and omalizumab have been attempted and shown a degree of success.
Unfortunately, some treatments like oral steroids, leukotriene receptor antagonists, antimalarial drugs, prostaglandin inhibitors, and oral beta-carotene do not seem to be effective in managing solar urticaria. In many instances, a combination of several treatment methods is needed to bring about and maintain relief from symptoms.
What else can Solar Urticaria be?
When trying to diagnose solar urticaria, or an allergic reaction to sunlight, doctors often have to rule out other conditions that can cause similar symptoms. These conditions can include:
- Polymorphous light eruption (an allergic reaction to sunlight)
- Lupus erythematosus (an autoimmune disease that causes your body to attack its own tissues and organs)
- Drug-induced photosensitivity (a reaction to medication that makes your skin more sensitive to sunlight)
- Photo contact dermatitis (inflammation of the skin caused by contact with certain substances and exposure to light)
- Porphyria cutanea tarda (a condition that causes skin blistering and fragility in sun-exposed areas)
It’s also worth noting that solar urticaria can be associated with other skin conditions caused by light exposure, like polymorphous light eruption and porphyria cutanea tarda.
What to expect with Solar Urticaria
Solar urticaria, also known as sun allergy, is a condition that’s not well understood yet. It’s pretty easy to diagnose, but managing it is quite tricky. This type of sun allergy generally starts in a person’s thirties and often turns into a long-term (chronic) disease. There are several ways to manage the symptoms, but complete disappearance of the disease often depends on a process called “hardening”. Not everyone achieves this state.
“Hardening” here refers to the phenomenon where the more a patient is exposed to ultraviolet radiation (the sun’s rays), the less likely they are to experience an outbreak of symptoms. Spontaneous resolution of this condition, which means the condition resolving on its own without treatment, is estimated to occur in about 15% of people five years after they first experience symptoms and in 25% of people ten years afterwards.
On the whole, people with a severe form of this sun allergy may have a challenging journey ahead. Many times, these patients end up spending most of their time indoors, which can take a toll on the quality of their life.
Possible Complications When Diagnosed with Solar Urticaria
Solar urticaria, or an allergic reaction to the sun, can cause serious health issues. This reaction is known as a type 1 hypersensitivity. If it results in a severe outbreak of solar urticaria, it may lead to fainting spells, difficulty breathing due to constriction of the airways, or even severe allergic reactions that cause numerous symptoms at once.
Common Side Effects:
- Fainting spells
- Difficulty breathing
- Severe allergic reactions
Preventing Solar Urticaria
Like other conditions that make your skin unusually sensitive to the sun, it’s important to stay protected from sunrays. Using a lot of broad-spectrum sunscreen on areas of skin exposed to the sun can help a lot. Wearing wide-brimmed hats and clothing that shields your body from sunlight is also advised to prevent outbreaks of solar urticaria, a type of skin rash that occurs after exposure to sunlight.