Photosensitivity

Photosensitivity or light sensitivity refers to an increased reactivity to light, which can lead to significant discomfort, disease, or injury in rare individuals. This condition can be influenced by various properties of light, such as timing, intensity, and wavelength. Additionally, some drugs may exacerbate photosensitivity. This summary provides an overview of the causes, conditions associated with photosensitivity, and the effects of different light sources.

Causes and Conditions

Photosensitivity can manifest through different physiological and psychological responses to light. Properties of natural or artificial light that may abnormally affect people include the timing of light, intensity of light, and wavelength of light. Rapid flickers in light intensity may also trigger or aggravate conditions such as photosensitive epilepsy, epileptic seizures, or migraine headaches. Other conditions related to light sensitivity include vertigo and chronic fatigue syndrome.

Sunlight

Sunlight, particularly ultraviolet radiation, can cause increased damage in predisposed individuals. Conditions associated with photosensitivity that may be exacerbated by sunlight include:

• Psoriasis
• Atopic eczema
• Mastocytosis
• Mast cell activation syndrome
• Histamine intolerance
• Erythema multiforme
• Seborrhoeic dermatitis
• Autoimmune bullous diseases (immunobullous diseases)
• Mycosis fungoides
• Smith–Lemli–Opitz syndrome
• Porphyria cutanea tarda
• Xeroderma pigmentosum

Additionally, many conditions are aggravated by strong light exposure, including:

• Systemic lupus erythematosus
• Sjögren syndrome
• Sinear–Usher syndrome
• Rosacea
• Dermatomyositis
• Darier's disease
• Kindler–Weary syndrome

Fluorescent and LED Lamps

Research by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) in 2008 looked at the links between fluorescent lamps, particularly compact fluorescent lamps (CFLs), and various human diseases. Key findings include:

• Ménière's disease, an inner-ear condition, can be aggravated by light flicker, and vertigo sufferers are advised to avoid fluorescent lights.
• Polymorphous light eruption, affecting 10-20% of the European population, can be triggered by artificial light sources like CFLs.
• Chronic actinic dermatitis, with a prevalence of 16.5 per 100,000 in Scotland, may worsen with CFL exposure.
• Systemic lupus erythematosus (SLE) patients may experience disease activity upon exposure to CFLs.
• Actinic prurigo, affecting 3.3% of the population, can be exacerbated by CFLs.
• Solar urticaria, a skin disorder affecting 3.1% of the population, can be directly affected by CFLs.
• Phytophotodermatitis may be aggravated by the UV light emitted by CFLs.
• Patients undergoing photodynamic therapy are at higher risk of adverse photosensitive reactions due to CFLs.
• One cause of cataracts is UV light exposure. Provided UV emission levels from lamps are within safe limits and the lamp is sufficiently distant, there should be no increased cataract risk.
• Photophobia, affecting 5 to 20% of the population, might be exacerbated by fluorescent lighting, which flickers at 100 times per second and is linked to headaches in office workers.
• Although no studies have been conducted on LED lights' effect on photophobia, LED flickering is more pronounced and may be more likely to cause headaches.
• There is evidence that light flicker can cause seizures in photosensitive epilepsy patients, but no specific evidence links seizures to CFLs.
• Self-reports suggest that fluorescent lamps may aggravate dyslexia.

Overall, understanding the impact of different light sources on conditions associated with photosensitivity is very important for managing and mitigating their effects. Controlled application of artificial light, such as through light therapy, can be beneficial in treating some disorders.

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Self-assessment MCQs (single best answer)

What is the term used to describe an increased reactivity to light in humans?

Which of the following conditions is NOT typically associated with sunlight-induced photosensitivity?

Which property of light is NOT mentioned as a factor that can exacerbate photosensitivity?

Which condition is particularly associated with vertigo and is advised to avoid fluorescent lights?

Which of the following is a skin disorder that affects 3.1% of the population and can be exacerbated by compact fluorescent lamps (CFLs)?

Which condition is mentioned as having disease activity potentially triggered by compact fluorescent lamps (CFLs)?

What is the prevalence of chronic actinic dermatitis in Scotland?

Which light source is suggested to have a more pronounced flickering effect that may cause headaches, especially in office workers?

Which of the following conditions is linked to an increased risk of adverse photosensitive reactions due to compact fluorescent lamps (CFLs)?

Which of the following statements is TRUE regarding the effects of light flicker?