Photosensitivity

Photosensitivity is an increased sensitivity of the skin to ultraviolet light, so that sun exposure produces a stronger reaction than usual, such as faster burning, redness, or irritation.

In skincare, the term often describes how certain ingredients can make skin more reactive to the sun. Exfoliating acids and retinoids, for example, are associated with a thinner, more vulnerable surface and greater sun sensitivity while in use. Some plant extracts and certain medications can also raise sensitivity, occasionally producing exaggerated reactions in exposed areas. A separate point is that some acids break down or become less effective in sunlight, which is one reason they are often used at night.

The practical response is consistent daily sun protection, which matters most when using these ingredients.

• Apply a broad-spectrum sunscreen with an adequate SPF each morning, and reapply during sun exposure, commonly suggested at roughly every two hours.
• Consider using known photosensitizing actives in the evening and supporting them with shade, hats, and protective clothing.

Photosensitivity is usually manageable rather than a reason to avoid effective ingredients altogether, but it makes sun protection non-negotiable while they are part of a routine. Reactions that are severe, blistering, or unexpected, or a strong response after starting a new medication, warrant medical advice, since some photosensitivity is drug-related rather than caused by skincare.