While we don't call these types allergic, the underlying process is much the same.Hives brought on by sunlight (photosensitive urticaria) may not seem like an allergic condition at first sight, but the evidence suggests it is.
Allergic urticaria is the name given to hives caused by allergic reactions to food, insect bites, medications, or makeup.
Other types are caused by physical irritation, such as sunlight, cold, or rubbing of the skin.
In many cases (at least half), the cause remains a mystery.
It usually doesn't matter, because hives are a brief, solitary event for most people.
The itching of hives can usually be rapidly relieved with antihistamines like hydroxyzine* or diphenhydramine. Other less sedating antihistamines (such as desloratadine, cetirizine, loratadine, or fexofenadine) may also be used for chronic hives or if acute hives last for more than 24 to 48 hours.