Definitions: Urticaria (hives), wheals, angioedema, pruritus (itchiness)
Urticaria. Urticaria (the medical term for hives) involves the sudden appearance of itchy wheals on the skin, either on the entire body or just one part of it. It may involve specific stimuli (e.g. cold or sunlight), or the wheals may appear spontaneously, i.e. without any apparent particular reason.
Wheals. Wheals is a term used to describe the skin when it looks like it has come into contact with stinging nettles. Freshly arisen wheals look like small whitish elevations on the skin surrounded by a red patch called the flare. Wheals consist primarily of water released from the blood vessels into the skin. This presses together the smallest blood vessels in the skin, allowing less blood to be transported through them and giving the skin a whitish hue (Ill. 1).
So-called giant wheals are lesions that coalesce to cover a large portion of skin. Wheals do not have to be whitish, nor must the surrounding skin be reddened: in some cases the exact opposite is true. In cases where wheals persist for more than a few hours, they often take on a reddish-brown hue, while the flare around them abates. Wheals can also take on other colours, such as the yellowish tones of the pencil-rubber sized wheals related to cholinergic urticaria (see below).
Angioedema. Simply put, angioedema involves whealing of the deeper layers of the skin. While whealing results from fluid escaping from the blood vessels directly under the skin's surface, with angioedema the "leak" is deeper. The borders of the corresponding lesion are less clearly visible and there is often no evident colour difference from normal skin. Angioedema frequently occurs in the face, hands, and feet (Ill. 2). The particular composition of the skin around the eyes and lips makes it particularly susceptible to severe swelling.
Pruritus (Itching). Beyond the fact that wheals and angioedema can lead to temporary but pronounced disfigurement, particularly in the face, pruritus or itchiness is the largest problem for patients with urticaria. Night itchiness above all else can be extremely bedevilling, since it robs the patient of sleep. The itchiness is especially bad for those patients suffering from a special, not uncommon form of urticaria called urticaria factitia. Scratching and rubbing of the skin brings on new wheals and continued itchiness, which soon turns into a vicious circle. The smallest stimulus of the skin, e.g. unconscious rubbing during sleep, can bring on fierce bouts of itchiness. Patients then report that they "scratched themselves to death."
Itchiness is exquisitely hard to ignore! Try keeping yourself from scratching the next time you have an itch somewhere, like a mosquito bite. Repetitive itchiness can (not unlike recurrent pain) become an enormous burden, and a significant diminishment of quality of life.