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Photosensitivity: Causes, Symptoms, Treatment, and Prevention

Sun sensitivity (a.k.a. Photosensitivity or Sun allergy) is a term used to describe diseases or health conditions that cause skin rashes whenever exposed to sunlight. It can be hereditary, induced, or can occur due to underlying autoimmune disorders.

Photosensitivity

What is Sun Sensitivity?

Sun sensitivity refers to an allergic reaction and people with sun sensitivity develop rashes when exposed to the sun. It is different from sunburn. Any person can develop sunburn or rash if exposed to sun for prolonged periods. But in patients with sun sensitivity, an allergic reaction is triggered when exposed to sun even for short time. Harmful rays such as ultraviolet (UV) rays from the sun result in skin damage.

Causes of Sun Sensitivity:

When the skin is exposed to the sun, UV light which fall on the skin triggers an immune reaction. The immune system releases inflammatory mediators in response leading to dilation of blood vessels of the skin. This process results in appearance of rash and other symptoms. Sun sensitivity can be classified into different types based on the underlying causes.

Exogenous photodermatoses: In this type, sun sensitivity is induced by drugs or chemicals. Based on the causes, drug-induced sun sensitivity is divided into two types:

  1. Phototoxicity or photoirritation: It is the most common type of sun sensitivity. Certain medications such as tetracyclines, fluoroquinolone, or sulfonamides may become toxic when exposed to sun. When a person takes these medications (either administered topically, orally, or intravenously), the allergic reaction may be triggered on the exposed skin within few hours of exposure.
  2. Photoallergy or photodermatitis: Certain cosmetics or skin care products such as sunscreens or lotions contain allergens that trigger allergic reactions when exposed to light. They make the skin more sensitive to light leading to occurrence of sunburn or rash. Sometimes, areas of skin that are not exposed to sun are also affected.

Certain foods and plants such as carrots, lime, parsley, and celery can cause photosensitivity.

Primary photodermatoses: Diseases such as solar urticaria (sun allergy rash), polymorphic light eruption (skin rash on exposure to UV light), and juvenile spring eruption (skin rash occurring in boys and young men on exposure to sun in early spring) result in sun sensitivity. Among these diseases, polymorphic light eruption (PMLE) is the most common cause of sun sensitivity.

Genetic photodermatoses: Sun sensitivity can be caused by genetic disorders such as xerodermapigmentosum and Bloom syndrome.

Metabolic photodermatoses: Sun sensitivity is triggered by metabolic disorders such as porphyria (

Photoexacerbateddermatoses: Autoimmune disorders such as psoriasis (build-up of skin cells into abnormal patches), systemic lupus erythematosus (chronic inflammatory disease that attacks joints and skin), acne rosacea (skin condition that cause pus-filled bumps on face), and atopic dermatitis (eczema or inflammation of the skin) can cause sun sensitivity.

Symptoms of Sun Sensitivity:

The symptoms of sun sensitivity range from mild to moderate depending on the cause and skin type. They last for 1 to 7 days and resolve on its own if further sun exposure is avoided.  Commonly affected sites are face, neck, arms, and legs. Symptoms are:

  • Red or bright pink rash
  • Itching or burning sensation at the affected site
  • Weeping or oozing (exudes a liquid that form crust)

Photoallergy may result in symptoms such as hives, small blisters, itchy rash, and peeling of skin.

Risk Factors of Sun Sensitivity:

People with lighter skin are more prone to sun sensitivity when compared to dark skinned people. Other factors associated with risk of sun sensitivity are:

  • History of systemic lupus erythematosus, psoriasis, or rosacea
  • History of porphyria
  • Genetic factors
  • Use of medications that sensitize the skin to sunlight such as
    • Antibiotics such as quinolones, sulfonamides, and tetracyclines
    • Tricyclic antidepressants
    • Antianxiety drugs such as alprazolam and chlordiazepoxide
    • Diuretics such as furosemide and thiazide
    • Phenothiazines
    • Antiarrhythymic agents such as amiodarone and quinidine
    • Antihyperglycemics such as sulfonylureas
    • Non-steroidal anti-inflammatory drugs such as ibuprofen, naproxen, and piroxicam
  • Use of perfumes, sunscreens, or skin care products containing antibacterials such as chlorhexidine and hexachlorophene

Diagnosis:

The healthcare provider examines the rashes on affected sites and enquires about the medical history, medications taken or skin care products used prior to the allergic reaction. This review can help in determining the cause of sun sensitivity. Tests that may be performed to confirm the diagnosis are:

Phototests: The skin is exposed to artificial UV light to see quickly and what minimum dose of light can cause rash. If the dose is very minimal, then a photosensitive disease is suspected.

Photopatch test: A substance or material that is considered to be causing sun sensitivity is pasted on skin and exposed to UV light. If rash develops within 24 to 48 hours of the exposure, then the test is considered positive for sun sensitivity.

Blood tests: Complete blood count, presence of porphyrins in blood, and presence of antinuclear antibodies may be investigated by obtaining a blood sample. These tests are performed to rule out underlying disorders such as porphyria and systemic lupus erythematosus.

Treatment of Sun Sensitivity:

Treatment for sun sensitivity helps to reduce the symptoms and treat the underlying disorder. Corticosteroids such as prednisone can be prescribed to reduce inflammation. Hydroxychloroquine (antimalarial agent) can also reduce symptoms.

To desensitize from sunlight, the healthcare provider may suggest you to gradually expose the skin to UV light for shorter periods of time. This therapy may take several weeks.

Prevention:

Limiting exposure to sunlight and artificial sources of UV light may help to prevent sun sensitivity. Other preventive measures are:

  • Stay indoors and avoid sunlight between 10 am to 4 pm as UV rays are highly intense during these hours.
  • Protect the skin as much as possible with clothes while going outdoors. Wear long-sleeved clothes, broad-brimmed hat, and sunglasses.
  • Avoid known medications or products that trigger sun sensitivity.
  • Check the contents of cosmetics or skin care products before using them.

FAQs:

1. Does sun sensitivity ever go away?

Sun sensitivity cannot be treated completely. Avoiding sun exposure is the prime solution to prevent it. However, gradual exposure to UV light can increase tolerance.

2. Is sun sensitivity dangerous?

Sun sensitivity is not life-threatening. But, the rashes may be unsightly and cause discomfort due to itching and oozing.

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1.
Photosensitivity. Healthline. https://www.healthline.com/health/photosensitivity#prevention. Accessed December 5, 2018.
2.
Photosensitivity. Dermnet NZ . https://www.dermnetnz.org/topics/photosensitivity/. Accessed December 5, 2018.
3.
Sunlight and skin damage. MSD manuals. https://www.msdmanuals.com/home/skin-disorders/sunlight-and-skin-damage/photosensitivity-reactions. Accessed December 5, 2018.

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