What is Photosensitivity?
Photosensitivity is a term used to describe a range of symptoms, diseases, and conditions (photodermatoses) that are caused or worsened by exposure to sunlight. There are five main types of photosensitivity: primary photodermatosis, exogenous photodermatosis, photo-exacerbated dermatoses, metabolic photodermatosis, and genetic photodermatosis.
In ‘primary or autoimmune photodermatoses’, your body’s immune system reacts to sunlight in ways such as polymorphic light eruption, juvenile spring eruption, actinic folluclitis, actinic prurigo, solar urticaria, chronic actinic/photosensitivity dermatitis, and hydroa vacciniforme (related to Epstein-Barr virus).
‘Exogenous or drug/chemical-induced photodermatoses’ is caused by external factors. Certain medications like thiazides, tetracyclines, NSAIDs (non-steroidal anti-inflammatory drugs), phenothiazines, voriconazole, quinine, vemurafenib can make your skin sensitive to sunlight. Additionally, certain chemicals found in plants, fruits, vegetables, cosmetics, dyes, disinfectants, and sunscreens (like psoralens) can cause photocontact dermatitis. Pseudoporphyria is another condition that can be triggered by medications or kidney problems.
‘Photo-exacerbated or photo-aggravated dermatoses’ are already existing skin conditions that get worse with sun exposure. It usually affects people with lupus, dermatomyositis, Sjogren syndrome, Darier disease, Rosacea, or Melasma. Sometimes, it can also worsen Pemphigus vulgaris, Pemphigus foliaceus, Atopic Dermatitis, Psoriasis, Lichen planus, Erythema multiforme, Mycosis fungoides and Seborrhoeic dermatitis.
‘Metabolic photodermatoses’ which are rare, are caused by disruptions in your body’s metabolism leading to reactions to sunlight. Disorders like Porphyria cutanea tarda, Erythropoietic protoporphyria, Variegate porphyria, and Erythropoietic porphyria (Gunther disease) fall under this category.
‘Genetic photodermatoses’ are very rare and caused due to genetic issues leading to instability at the genomic level that cause reactions to sunlight. Disorders like Xeroderma pigmentosum, Cockayne syndrome, Trichothiodystrophy, Bloom syndrome, and Rothmund Thomson syndrome fall under this category.
What Causes Photosensitivity?
The cause of a skin reaction to sunlight, also known as photodermatosis, depends on its type (referring to other specific articles for details). Several factors can cause photodermatosis including: reactions by the body’s immune system, certain medications, connective tissue diseases, and abnormal inherited body chemical processes.
Risk Factors and Frequency for Photosensitivity
Photosensitivity, or increased sensitivity to sunlight, can be experienced by anyone, regardless of gender, age, or ethnic group. Different types of photosensitivity can be more common at certain stages of life. Both genes and environmental factors can influence whether a person develops photosensitivity.
Signs and Symptoms of Photosensitivity
Photodermatoses or skin conditions caused by exposure to sunlight commonly affect areas that are typically exposed such as the face, neck, and hands. However, they do not usually affect areas that are concealed by clothing. Interestingly, these skin conditions may also occur in areas that are often brought to light, like in polymorphic light eruptions. Some types only affect specific body parts, such as juvenile spring eruptions that are found only on the tops of the ears. Moreover, photodermatoses can also result from indoor exposure to artificial sources of ultraviolet radiation like fluorescent lamps. A notable health risk is the genomic instability due to DNA repair deficiency diseases, which can cause changes to skin color and increase the risk of skin tumors, including basal cell carcinoma, squamous cell carcinoma, and melanoma by up to 1000 times.
Kids with photosensitive genodermatoses or skin disorders due to light sensitivity usually have distinctive skin features and abnormalities in other organs.
Signs of photosensitivity may include:
- Worsening symptoms during summer. It’s good to note, though, that many photodermatoses occur throughout the year.
- Clear distinction between the area affected and the skin covered by clothing or jewellery such as a watch strap or ring.
- Not affecting the folds of the upper eyelids.
- Not affecting the deep wrinkles on the face and neck.
- Not affecting the skin concealed by hair.
- Not affecting the skin under the shadow of the ears, nose, and chin.
- Sparing the area between the fingers, commonly known as the web spaces.
Testing for Photosensitivity
If you’re experiencing sensitivity to sunlight, doctors diagnose this condition, known as photosensitivity, by looking at your history of skin issues caused by sun exposure. They figure out the specific type of photosensitivity by asking you questions about your history, examining your skin, and conducting particular tests. Some of these tests are often only available at specialized facilities.
One of the tests they might use is called Minimal erythema dose (MED) testing. MED testing involves exposing the skin to either a range of light wavelengths (broadband) or a specific light wavelength (monochromators) to find out the smallest dose of light that causes sunburn.
Moreover, doctors might carry out a provocation photoset procedure. In this test, they expose your skin to specific types of light, known as UVA and UVB, over four days to try and recreate the skin issue.
Photopatch tests, which are similar to standard skin patch tests, might also be used to pinpoint any photoallergies – allergies triggered by sunlight.
As part of the process, doctors might conduct some additional tests as well:
– They could ask for a full blood count, which gives an overview of the different types of cells in your blood.
– They might test for connective tissue antibodies, such as antinuclear antibodies (ANA) and extractable nuclear antigens (ENA), if they suspect you have lupus erythematosus, a disease where the body’s immune system attacks its own healthy cells.
– To detect substances called porphyrins, which can make your skin sensitive to the sun, tests on your blood, urine, and feces might be performed.
– If porphyria is a concern – a group of rare genetic disorders that affect the nervous system or skin – they may also conduct liver function and iron tests.
– In some cases, a skin biopsy might be necessary to confirm the diagnosis.
Doctors might also look into more specialized tests if there’s a suspicion of certain less common conditions. For instance, if xeroderma pigmentosum is suspected, which makes you severely sensitive to sunlight, they might measure your body cells’ survival and DNA repair capacity after UV light exposure. If they suspect trichothiodystrophy, a condition characterized by brittle hair and skin problems, they might examine hair under a microscope, which may show a “tiger hair” appearance. They’d then conduct further tests to confirm this.
Lastly, gene sequencing might also be used to diagnose conditions like Bloom syndrome or Rothmund Thomson syndrome if there are any suspicions. These conditions can make your skin extremely sensitive to the sun and cause other health issues.
Treatment Options for Photosensitivity
Managing sensitivity to light, also known as photosensitivity, involves protection from the sun and treating the cause of the sensitivity. Prevention mainly relies on protection from sunlight and avoiding artificial sources of ultraviolet radiation (UVR), a type of radiation from the sun and some artificial sources that can cause burns or injure skin cells. Websites and smartphone apps that give information about local levels of ultraviolet radiation can be a useful tool to know when to take extra precautions.
It’s important to know that ultraviolet radiation is stronger in tropical areas compared to temperate places, in the Southern part of the world compared to Northern, during summer compared to winter, at high altitudes compared to sea level, and in midday compared to the morning or evening.
You can protect yourself by:
- Avoiding direct sunlight whenever possible
- Staying indoors, away from windows, and seeking shade when outdoors
- Dressing in clothing that covers your body and wearing a wide-brimmed hat when outdoors. Some clothing has a label called ultraviolet protection factor (UPF) that indicates how well it blocks UVR. Thick, tightly woven, dry, and dark-colored polyester, denim or wool provide the best protection
- Using a broad-spectrum sunscreen with an SPF (Sun Protection Factor) of 50 or higher on all exposed skin. This type of sunscreen protects from both types of UVR, known as UVA and UVB, and is resistant to water. It should be applied generously and reapplied every two hours while outdoors
- Using tanning products that include dihydroxyacetone, which can provide modest protection against UVA and to a lesser extent against UVB – the two types of ultraviolet radiation the sun emits.
SPF stands for sun protection factor. It represents how well a sunscreen can protect the skin from sunburn. Specifically, it shows how much sun exposure it takes to burn skin covered with sunscreen compared to skin without sunscreen. SPF mainly indicates protection from UVB radiation, the type of UVR that causes redness and sunburn.
A common skin reaction to sunlight known as polymorphic light eruption can actually be treated effectively by careful, gradual exposure to ultraviolet radiation. This process should be done cautiously and in a controlled manner.
What else can Photosensitivity be?
When it comes to diagnosing photosensitivity, which is an extreme reaction to sunlight or other sources of light, a doctor will first consider different categories of photosensitivity-related conditions:
- Primary photosensitivity such as polymorphous light eruption
- Autoimmune photosensitivity such as lupus erythematosus
- Photo-exacerbated or aggravated conditions such as dermatomyositis
- Genetic conditions like xeroderma pigmentosum
- Metabolic disorders like porphyria cutanea tarda
Next, the doctor applies details from the patient’s history and physical exam to zero in on the specific condition. For instance, a doctor might distinguish polymorphous light eruption (a type of primary photosensitivity) from lupus erythematosus (an autoimmune condition) by closely examining the patient’s history, symptoms, and skin lesions.
In the case of photo-exacerbated diseases like dermatomyositis, other clinical signs can also be key to a diagnosis. The presence of capillary abnormalities around the nail folds or Gottron papules (raised, reddish patches) over the bony parts of the hand, for example, can help differentiate it from drug-induced photosensitivity and other conditions. Once the doctor has identified the broader category of photosensitivity the patient’s condition might fall under, they can then focus on working out the specific diagnosis within that category.
For more detailed information on diagnosing each specific photosensitivity-related condition, consult dedicated resources specific to that condition.
What to expect with Photosensitivity
Each medical condition has its own unique outcome. For more information about a specific condition, please refer to its individual chapter.
Possible Complications When Diagnosed with Photosensitivity
Each condition has its own unique complications. To learn more about each one, please refer to the specific chapter related to each condition.
Preventing Photosensitivity
In simple terms, the treatment of photosensitivity, no matter the specific condition, primarily focuses on relieving symptoms and promoting protection from light. Photosensitivity is a condition where the skin reacts excessively to sunlight or artificial light.
