Photosensitive dermatitis is a condition that causes skin inflammation, or an eczematous reaction, after exposure to sunlight or some types of artificial light.

It can affect people of all ages and skin types and occurs due to an abnormal reaction to some component of the electromagnetic spectrum of sunlight, which includes UV and visible light. People with photosensitive dermatitis typically cannot expose themselves to direct sunlight and even some forms of artificial light without their skin reacting.

In this article, we discuss photosensitive dermatitis, including the symptoms, causes, and treatments.

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Photosensitive dermatitis is a condition where a person’s skin develops unusual reactions, such as eczematous eruptions, in response to UV radiation, visible light, or both in sunlight and artificial light sources. Photosensitive refers to a reaction to light, while dermatitis is the term for inflammation of the skin.

Some people may also refer to photosensitive dermatitis as photosensitivity, photodermatosis, photodermatitis, sun allergy, photoallergy, or chronic actinic dermatitis.

There are currently no data on the incidence and prevalence of photosensitive dermatitis, as diagnoses are rare. This is likely due to potential misdiagnoses — it may start as atopic dermatitis without any signs of photosensitivity, or people may associate it with sunburns or excessive sun exposure.

Experts can characterize photosensitive dermatitis by “photodistributed” lesions and skin eruptions. These appear at sun-exposed parts of the skin, such as the outer part of the arms and hands, the chest, and the back and side of the neck.

Areas that typically do not receive sun exposure, such as the folds of the upper eyelids, the webspaces between fingers, and the shadowed areas under the nose and chin, do not usually develop these lesions.

The condition may also resemble an exaggerated form of sunburn, but the reactions occur even with less intense light exposure. The appearance of symptoms following light exposure may also be instant or delayed.

In photosensitive dermatitis, a phototoxic or photoallergic reaction causes the individual’s abnormal response to sunlight. Both reactions occur due to topical treatments or medications in the person’s body.

Phototoxic reactions

Phototoxic reactions are a common type of photosensitivity reaction. Here, a person takes medications, such as systemic agents, or applies skin care products that contain photosensitizing agents, which react to UV light exposure.

Skin damage looks and feels similar to sunburns and rashes and is well-defined. The skin reaction often appears within minutes to hours, but it may take days in some cases. With a sufficient chemical dose and light exposure, it can happen to anyone.

Photoallergic reactions

Less commonly, and in contrast to phototoxic reactions, photoallergic reactions involve immune hypersensitivity. Here, the UV light interacts and changes the structure of a chemical or an antigen after a person takes it or applies it to their skin.

The immune system detects the change, sees it as a threat, and forms antibodies to attack it. Photodistributed rashes, blisters, and oozing lesions may appear a few days after light exposure.

Sometimes, chemicals may induce both phototoxic and photoallergic reactions in people. Common chemical agents that may cause reactions include fragrances, certain chemicals in some sunscreens, tar products, light-sensitive drugs called psoralens, and antiseptics. This reaction may also occur with certain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) and retinoids.

Besides chemical and drug-induced reactions, photosensitive dermatitis may also be hereditary or due to an underlying medical condition. A 2019 study suggests that older adults are at risk for developing photosensitivity reactions. It also notes that more than one-fifth of their medications are potentially phototoxic, photoallergic, or both.

People may not directly associate the appearance of eruptions or lesions on their skin with light exposure, especially if the reaction is not instant.

To confirm the diagnosis of photosensitive dermatitis, doctors will ask questions about previous sun exposure, exposure to photosensitizing agents, family history, and any other symptoms. They will also examine the skin and look at the distribution of skin lesions to help rule out other forms of photosensitivity. Further evaluations include phototesting and photopatch testing.

In phototesting, an individual’s skin receives increasing doses of UVA and UVB light exposure. In photopatch testing, medical practitioners apply two sets of photoallergen. The practitioners will irradiate one allergen and use the other as a control. A dermatologist can also perform a skin biopsy and other laboratory investigations.

The evaluation will define the specific type of photodermatoses affecting an individual. It also aims to rule out other conditions, such as porphyria, systemic lupus erythematosus, and pellagra. Blood tests including a complete blood count can also help rule out other conditions.

The main form of treatment for photosensitive dermatitis will typically include prevention methods, such as using sun protection, avoiding contact with any known allergens, and stopping any photosensitizing drugs if possible. This may involve staying inside, fully covering the skin, using broad-spectrum sunscreens, and taking photoprotective medications.

To treat any eczematous reactions, doctors will likely suggest similar options to other forms of eczema, such as emollients and topical steroids. In cases of severe dermatitis, doctors may suggest stronger medications, such as oral corticosteroids or immunosuppressive agents.

The Skin Cancer Foundation recommends that people with skin rashes who develop weakness, headaches, a fever with chills, and flu-like symptoms after sun exposure see their doctor. The skin rashes may indicate photosensitivity or be a symptom of a different condition, and they may require immediate attention and examination.

People who develop blistering, painful sunburns should also seek medical attention, as these are equivalent to second degree burns and require treatment.

Photosensitive dermatitis may interfere with a person’s lifestyle and mean they spend more time inside to reduce sun exposure. This could lead to isolation and the inability to go out, especially during summer and sunny holidays.

As a result, a 2020 study shows that people with photosensitive disorders are prone to vitamin D deficiency. An older study demonstrates that the condition could also negatively influence their lifestyle, including employment status.

Furthermore, a 2021 study notes a potential association between phototoxic drugs, such as NSAIDs, antimicrobials, antihypertensives, and antineoplastic drugs, and a possible increased skin cancer risk.

The management of the condition involves wearing sun protection and avoiding exposure to the sun and artificial light sources. Steps that a person can take include:

  • staying indoors
  • avoiding exposure to direct sunlight or staying in shaded areas when outdoors
  • wearing wide-brimmed hats and fully covering the skin with densely woven clothing
  • using broad-spectrum sunscreens with an SPF of 50 or above

Photosensitive dermatitis is a skin condition where a person’s skin reacts abnormally to light, resulting in an eczematous reaction. This may occur after taking or applying specific photosensitizing agents.

People can try to prevent it by following sun-protective steps, such as applying broad-spectrum sunscreens, wearing protective clothing, and avoiding sun exposure when possible. Certain drugs may also make a person’s skin photosensitive. In these cases, a person should discuss changing their medication with their doctor.