What is a common trigger for solar urticaria?

Solar urticaria is a type of physical urticaria characterized by the development of hives or wheals in response to solar exposure. The condition is directly related to specific wavelengths of light, particularly ultraviolet (UV) radiation. When the skin is exposed to certain wavelengths, it can trigger an immune response in susceptible individuals, leading to the release of histamine and other mediators that cause itching, swelling, and redness.

The other listed triggers, such as high temperatures, cold temperatures, and chemical irritants, are associated with different types of urticaria or skin reactions. High temperatures are more commonly linked to heat-induced urticaria, while cold temperatures can provoke cold urticaria. Chemical irritants may cause contact dermatitis but are not a primary concern for solar urticaria specifically. Hence, the correct answer highlights the unique mechanism of solar urticaria connected to specific light wavelengths.