photopatches

Photopatches is a term applied in several fields to describe patch-like elements that interact with light. The concept encompasses diagnostic tools used in dermatology as well as flexible, light-sensitive devices in materials science and wearable technology. Because the same term covers different implementations, context is important when interpreting references to photopatches.

In dermatology, photopatch testing is a standardized diagnostic procedure for identifying substances that cause photosensitive or photoallergic contact dermatitis. Small patches containing potential allergens are applied to the skin, typically on the back, and then exposed to controlled ultraviolet or visible light. Readings are taken at set intervals, commonly around 24 and 72 hours after exposure, to observe any light-induced skin reactions. Positive results help clinicians determine whether a patient’s dermatitis is related to a light-activated allergen. Photopatch testing is usually used in conjunction with conventional patch testing and photosensitivity histories to guide avoidance strategies and treatment.

In materials science and wearable technology, photopatches refer to thin, flexible patches that integrate light-sensitive components such as photodiodes, organic or perovskite semiconductor layers, or photoresponsive polymers. These patches can function as light sensors, energy harvesters, or components in optoelectronic systems. They are typically fabricated on flexible substrates and may be designed for skin-mounted use, environmental sensing, or integration into textiles. Common considerations in their development include material stability, encapsulation to protect against moisture, mechanical durability, and safe, compatible adhesion.

See also: patch testing, photodetectors, optoelectronics, wearable sensors.