Urticaria is a skin reaction that causes a raised, itchy rash. It is also known as hives or nettle rash. It can appear on one part of the body or cover large areas, but in most cases, it usually settles within a few days. It occurs when a trigger causes high levels of histamine to be released into the skin, resulting in swelling and itchiness. The trigger can be a certain food or food additive, an insect bite, heat, cold, exertion or even stress. It affects women twice as much as men. Treatment with antihistamines can relieve the discomfort and you can also cool the affected area with a cold shower, a fan, a cool cloth or a soothing lotion. However, seek emergency care if you feel dizzy, if you have any trouble breathing or feel any swelling in your tongue or throat.