Photosensitivity

What Is Photosensitivity?

Photosensitivity is a condition where a person has an unusually strong reaction to light exposure. This can include discomfort, headaches, rashes, or, in severe cases, seizures—especially when exposed to bright, flickering, or flashing light.

Common Causes

Causes include medical and genetic conditions, medications and treatments, and skin disorders.

Medical and Genetic Conditions

Some individuals are born with or develop conditions such as xeroderma pigmentosum or porphyria. Inherited eye disorders like retinitis pigmentosa can also heighten light sensitivity.

Medications and Treatments

Certain drugs—such as some antibiotics, antihistamines, and NSAIDs—can cause photosensitive side effects. Cancer treatments may also increase sensitivity.

Skin Disorders

Conditions like lupus, eczema, and dermatitis can make the skin reactive to light, leading to inflammation or rashes upon exposure.

Photosensitivity in Web Accessibility

Rapid flashing visuals, high-contrast patterns, and bright themes can be harmful to users with photosensitivity. These triggers may result in discomfort or neurological symptoms like seizures.

WCAG Guidelines for Flashing Content

WCAG recommends that content should not flash more than three times per second, flashes must remain below both general and red flash thresholds, and moving elements must be able to be paused, stopped, or hidden by users.

Design Best Practices for Photosensitivity

Avoid rapid flashing, blinking animations, or fast-changing visuals. Clearly label or warn users before showing potentially triggering content. Use consistent, simple layouts. Provide user settings to pause animations, dim brightness, or adjust contrast. Ensure readable contrast and include text alternatives. Involve users with photosensitivity in usability testing.