Can you explain the relationship between allergies and urticaria?

Allergy & Hives. Urticaria, or hives, are caused by release of histamine in the skin; this leads to itching and a raised rash. Histamine is also released in allergic reactions; in the nose it causes drainage & sneezing while in the lungs it causes wheezing & tightness. Hives can be due to an allergic response to a food or medicine but they can also be a contact response or due to direct histamine activation.
Skin reaction. Urticaria is the medical term for hives, which are an allergic skin reaction.