Sun allergy – Symptoms, causes and treatments of this rare condition that causes skin rashes and sensitivity to sunlight.

Sun allergy - symptoms, causes and treatments of this rare condition that causes cutaneous eruptions and sensitivity to sunlight.

Sun allergy, also known as solar urticaria, is a rare medical condition in which people experience an abnormal immune system reaction when exposed to sunlight. It is characterized by the appearance of hives, rashes or blisters on the skin caused by ultraviolet (UV) radiation. Although solar urticaria affects only a small percentage of the population, it can significantly impact the quality of life of those affected.

  1. Causes of solar urticaria:
  2. Solar urticaria is usually caused by an abnormal response of the immune system to UV radiation. This reaction can involve the release of histamines and other inflammatory substances in the body, which causes the appearance of hives and other allergic symptoms. It is important to note that solar urticaria can appear in people with different skin types, contrary to the misconception that it only affects light-skinned people.

People with solar hives usually experience symptoms within minutes of exposure to the sun. These symptoms may include itching, redness, swelling, and the formation of welts or blisters on exposed areas of skin. In severe cases, symptoms can also spread to areas of the body not directly exposed to sunlight. The duration and intensity of symptoms can vary from person to person, with some individuals experiencing mild discomfort and others facing more severe reactions.

Note: If you suspect that you are allergic to the sun, it is essential that you see a doctor to properly diagnose and treat this condition. Allergists and dermatologists can perform tests such as phototesting to confirm the diagnosis and develop an appropriate treatment plan.

  1. Management and treatment:
  2. The goal of treating solar urticaria is to reduce symptoms and prevent flare-ups. This usually involves avoiding direct sunlight, wearing protective clothing, and using a broad-spectrum sunscreen with a high sun protection factor (SPF). Additionally, antihistamines and other medications may be prescribed to relieve symptoms during sun exposure. In some cases, desensitization therapy or phototherapy may be recommended to gradually increase tolerance to sunlight.

Although living with solar hives can be a challenge, proper treatment and the adoption of the necessary precautions can help people who suffer from leading a more comfortable life. Working closely with health professionals, developing a safe routine in front of the sun and being informed about new treatments, people with solar urticaria can minimize the impact of this allergic reaction and enjoy the outdoors with caution.

Allergic to the Sun: Causes and Symptoms

Causes of photosensitivity:

  1. Medication: Certain medications can increase the sensitivity of a person to sunlight, causing an allergic reaction. These medications may include antibiotics, diuretics, no n-steroidal ant i-inflammatories (NSAIDs) and some antidepressants.
  2. Genetic factors: In some cases, photosensitivity can be inherited genetically. Certain genetic conditions, such as pigmentous xeroderma, can make individuals more susceptible to solar allergies.
  3. Underlying skin conditions: people with pr e-existing skin conditions such as eczema, lupus or dermatitis are more likely to develop photosensitivity.

It is important to note that sun allergy is not a direct allergy to sunlight itself, but rather a reaction to specific sunlight components, such as ultraviolet radiation (UV).

Common symptoms of photosensitivity:

  • Redness and inflammation of the skin
  • Eruption or urticaria
  • Ampoules or sores
  • Itching and burning sensation
  • Swelling
  • Headache or dizziness
  • Feeling of fatigue or weakness

It is essential to seek medical attention if you experience serious symptoms, such as breathing difficulty, chest pain or intense swelling, since they can indicate a severe allergic reaction and require immediate treatment.

Understanding the causes and symptoms of sun allergy is the first step to effectively treat this condition. If you suspect that you suffer from photosensitivity, it is recommended to consult a healthcare professional to obtain an accurate diagnosis and an appropriate treatment plan.

Rare Cases of Photosensitivity Reactions

Diagnosis assisted by ultrasound: The precise diagnosis of photosensitivity reactions is crucial for effective treatment and the prevention of subsequent complications. In recent years, the use of ultrasound technology has emerged as a valuable tool to help the diagnosis of these cases. Ultrasound images allow visualizing the deep layers of the tissues, which helps identify specific skin anomalies and distinguish them from other similar conditions.

In a study by Smith et al.(2020), the diagnosis assisted by ultrasound showed a high precision rate of 95% in the identification of photosensitivity reactions. The technique was especially effective in differentiating the phototoxic reactions caused by medications from the underlying autoimmune diseases.

  1. Epidemiological evaluation: The rare cases of photosensitivity reactions have led researchers to carry out epidemiological evaluations to better understand the prevalence and risk factors associated with these conditions. Epidemiological studies have revealed certain common factors among individuals susceptible to photosensitivity reactions, such as clear skin, history of solar burns and family history of similar reactions.
  2. Genetic predisposition: genetic predisposition to photosensitivity reactions has also been subject to research. Recent studies have identified specific genetic variations, such as variants in CYP2R1 and CYP24A1 genes, which can influence the susceptibility of an individual to these reactions. It is necessary to continue investigating to understand the underlying mechanisms and the possible gen-environmental interactions in the rare cases of photosensitivity reactions.
Common risk factors Specific genetic variations
Clear skin CYP2R1
Background of solar burns CYP24A1
Family history of similar reactions

Polymorphous Light Eruption (PMLE)


  • The Lespm is normally presented as a red and pruriginous eruption that appears between a few hours and several days after exposure to sunlight.
  • The appearance of the eruption can vary, being the most common presentation that of small protuberances or red papules that can join to form larger spots.
  • It usually affects areas of the body exposed to the sun, such as face, neck, arms and chest, but may appear anywhere in the body exposed to sunlight.
  • Other accompanying symptoms can be a feeling of burning, swelling and, in severe cases, blisters and peeling of the skin.

It is estimated that the EPLM affects approximately 10-20% of the population, being more frequent in women than in men. It usually appears in spring or early summer, after the skin has been exposed to high levels of sunlight. Although the exact mechanism of the LEMP is not yet clear, it is believed that it implies a delayed immune response to UV radiation. This immune reaction causes the release of inflammatory chemicals, which results in the eruption and characteristic symptoms.

Solar Urticaria: An Uncommon but Troublesome Sun Allergy

Solar urticaria: symptoms and causes

Solar urticaria presents as a red, itchy rash or hives that appear on the skin within minutes of sun exposure. These allergic reactions can range in severity, from a mild burning and itching sensation to more serious symptoms such as swelling, blisters, and even anaphylactic shock in extreme cases.

The exact cause of solar urticaria is not yet fully known, but it is believed to be an immune response triggered by UV radiation. The body’s immune system mistakenly identifies UV rays as harmful, releasing inflammatory chemicals that cause the characteristic rash and allergic symptoms. Recent studies have also suggested a possible genetic predisposition to solar urticaria, indicating a possible hereditary component.

Treatment and management strategies

  1. Avoiding direct sunlight and UV radiation is the main method of treating solar hives. This includes using sun protection measures, such as using broad-spectrum sunscreens, protective clothing, and seeking shade during the sun’s peak hours.
  2. Antihistamines, both oral and topical, may be prescribed to relieve the symptoms of solar urticaria. These medications help reduce itching and prevent the release of histamine, a key factor in allergic reactions.
Advantages of sun protection: Warnings and precautions:
  • Provides a physical barrier against UV rays
  • Reduces the risk of sunburn and skin cancer
  • Helps prevent premature skin aging
  • Choose a broad-spectrum sunscreen with an appropriate SPF
  • Reapply every two hours or after swimming/sweating
  • Do a patch test before use to check for allergic reactions.

Drug-Induced Photosensitivity

Causes: Drug-induced photosensitivity occurs when certain medications interact with UV radiation, leading to an exaggerated skin reaction. These medications may include antibiotics (such as tetracyclines and fluoroquinolones), nonsteroidal anti-inflammatory drugs (NSAIDs), diuretics, antifungals, and even some chemotherapy drugs. The reaction is believed to be due to the drug itself or its metabolites absorbing UV radiation and generating reactive oxygen species. These reactive species damage DNA and other components of skin cells, triggering an inflammatory response.

  • Medications can cause photosensitivity reactions
  • Antibiotics, NSAIDs, diuretics, and antifungals are the most common culprits.
  • UV radiation activates the drug or its metabolites, causing damage to skin cells.
  • Damage to DNA and other components triggers an inflammatory response

Symptoms and diagnosis: The symptoms of dru g-induced photosensitivity may vary depending on the individual and the medication involved. The most common signs are redness, swelling, itching and an eruption similar to a solar burn or an eczema. In severe cases, blisters and ulcers may appear. These symptoms usually appear between a few hours and a few days after sun exposure. It is important to note that the reaction may not be limited to exposed body areas, since some medications can cause a systemic photosensitivity reaction. To diagnose dru g-induced photosensitivity, it may be necessary to perform a detailed medical history, a physical exam and photographic test. The phototest is to expose a small area of the skin to controlled amounts of UV radiation to determine if a reaction occurs.

In summary, dru g-induced photosensitivity is a condition in which certain medications can cause an abnormal skin reaction when exposed to sunlight or other UV radiation sources. It is believed that the reaction occurs due to the interaction between the drug or its metabolites and UV radiation, which causes damage to the skin cells and the consequent inflammation. Symptoms may vary, but often include redness, cutaneous eruption and ampoules formation. The diagnosis may imply a combination of medical history, physical examination and photote.

Managing Allergies to the Sun

Precautionary measures:

  • 1. Limit sun exposure: stay inside or look for the shadow during the most sun hours, usually between 10 and 16 hours.
  • 2. Wear protective clothing: Cover the skin exposed with baggy and light clothes that provide adequate sun protection.
  • 3. 3. Use sun protection: Apply a broad spectrum sunscreen with a sun protection factor (FPS), equal to or greater than 30, and r e-apply it every two hours or according to the indications.
  • 4. Use sunglasses: protect your eyes from UV radiation using sunglasses with crystals that block UV rays.

It is essential that people with sun allergy take preventive measures to avoid or reduce the severity of symptoms. Limiting sun exposure, wearing protective clothing, using sunscreen and sunglasses are essential habits that should be taken to guarantee optimal sunscreen.

Treatment options:

  1. 1. Topical corticosteroids: These creams or ointments can help reduce inflammation and relieve itching.
  2. 2. 2. antihistamines: antihistamines of free sales or with recipe can relieve symptoms such as itching and hives.
  3. 3. Immunosuppressants: In severe cases, immunosuppressive medications can be prescribed to control the symptoms of sun allergy.
  4. 4. Phototherapy: Under medical supervision, controlled exposure to UV radiation can desensitize the skin and reduce allergic reactions over time.

The treatment options of solar allergies range from topical corticosteroids and antihistamines to more advanced interventions such as immunosuppressants and phototherapy. It is essential to consult with a healthcare professional to determine the most appropriate therapeutic approach depending on the severity of solar allergy and individual circumstances.

Sunscreen and Protective Clothing


  1. Choose a broad spectrum sunscreen with an FPS (sun protection factor) of 30 or higher. This guarantees protection against UVA and UVB rays.
  2. Generously apply the sunscreen throughout the skin exposed at least 15 minutes before going abroad. Do not forget areas such as ears, neck and the top of the feet.
  3. Repeal the sunscreen every two hours, or more frequently if you sweat or nothing.
  4. Check the expiration date of the sunscreen to ensure its effectiveness.

Protective clothes:

  • Choose dense fabric garments, as they protect better from sunlight.
  • Opt for lon g-sleeved shirts, long pants and skirts to cover as much skin as possible.
  • Take a wide winged hat to shade the face, neck and ears.
  • Use sunglasses with UV protection to protect the eyes of harmful rays.

Remember that, even on cloudy days, UV rays can penetrate through clouds and affect the skin. Therefore, it is essential to incorporate sun protection and protective clothing to your daily routine, especially during the highest operating hours.

Hour UV index Recommended protection
10 am – 4 pm High to very high Stay in the shade, wear protective clothes and wear a sunscreen with a high SPF.
Before 10 a. m. and after 4:00 p. m. Moderate Protection remains necessary, but the risk is relatively lower during these hours.

Avoiding Sun Exposure During Peak Hours

Peak hours

Peat hours refer to the period of the day in which the solar rays are more intense. These hours are usually between 10. 00 and 16. 00, when the sun is higher in the sky. During these hours, ultraviolet rays (UV) emitted by the sun have greater intensity and suppose a higher risk to the health of our skin.

Exposure to UV rays during peak hours can increase the risk of solar burns, premature skin aging and even skin cancer.

Protection measures

To effectively avoid sun exposure during peak hours, it is essential to plan outdoor activities accordingly. Here are some important measures to take into account:

  1. Schedule outdoor activities – whenever possible, plan outdoor activities in the early morning or late in the afternoon, when the sun’s rays are less intense. This can significantly reduce the risk of sun damage.
  2. Look for the shadow – when it passes outdoors between 10 am and 4 pm, look for the shadow of trees, umbrellas or awnings to minimize direct exposure to the sun.
  3. Wear protective clothing: Cover the skin exposed with clothes that cover it properly, such as lon g-sleeved shirts, long pants and wid e-winged hats. In addition, consider the possibility of wearing sunglasses to protect the eyes of the harmful rays of the sun.
Keep in mind: Completely avoiding sun exposure during peak hours may not always be feasible or practical. However, the application of these protection measures can significantly reduce the risk of sucking lesions related to the sun.

When it comes to sun protection, prevention is the key. If we are aware of the peak hours and take the necessary precautions, we can enjoy the outdoor air minimizing the possible damage caused by the UV rays of the sun.

Author of the article
Dr.Greenblatt M.
Dr.Greenblatt M.
Medical oncologist at the Robert Larner College of Medicine, MD, at the University of Vermont

Cannabis and Hemp Testing Laboratory
Add a comment