Hives

Key points
Commonly referred to as hives, condition results in spontaneous weals appearing anywhere on the body.
Condition can vary in duration, color, texture, and pattern of weals, as well as secondary symptoms.
Condition is classified by duration of weals.
There are many, many causes of weals, and in some instances may be multiple causes working in tandem.

General ordinary uticaria, more commonly referred to as hives, results in spontaneous weals (raised marks or blemishes on the skin) appearing anywhere on the body. This is typically due to the release of chemicals such as histamine from agitated mast cells. The weals can be small or large, red or white colored, surround by redness and frequently itchy. They may last a few minutes or a few hours, and may change shape. They may be round, form rings, a map-like pattern or giant patches. These weals may be accompanied by a deeper swelling of eyelids, lips, hands, and other areas. In rare instances, the urticaria may result from an autoinflammatroy disease such as systemic lupus, erythematosus, or Schnitzler syndrome, or an inherited condition such as Muckle-Wells syndrome or cryopyrin-associated periodic syndrome.

Urticaria is often classified according to how long it has been present. Acute urticaria is typically recent onset (hours, days or a few weeks), episodic urticaria describes intermitten attacks lasting a few days or weeks, and chronic urticaria persists for several months or years.

Urticaria may not be present all the time — some find it more noticeable at certain times of day or during periods of warmth or emotional upset. Acute urticaria can be sometimes due to allergic reaction, causing an release of chemicals in the mast cells. Common allergic reactions are to medicine, food allergies, bee or wasp stings, or skin contact with an allergin (e.g. rubber latex). Most cases of urticaria are not allergy related. Non-allergic causes of Urticaria include infection, serum sickness due to blood transfusion or viral infection (which would be accompanied by fever, swollen glands, painful joints, and nausea), medicines such as morphine or other opiates and radiocontrast agents, and non-allergic food reactions from food additives and bacterial decomposition. Chronic urticaria is often due to autoimmune disease and other autoimmune conditions such as Thyroid disease and celiac disease. In rare cases, it may be due to C1 esterase deficiency, which would be evident in family history. Urticaria should be distinguished from urticarial vasculitis which causes weals to persist for longer than 24 hours and can be determined through skin biopsy.

Some forms of urticaria are caused by external physical influences with unknown causes. Dermographism, or skin writing, occurs when the skin is stroked, causing weals to appear where the stroking occurred. It is extremely itchy, which in turn causes more weals, or where skin is contacted by clothing or excessive warmth. Cholinergic Urticaria results from sweating, causing hundreds of tiny red itchy spots to develop after periods of exertion, warmth or concentration. Cold urticaria affects skin warming up after periods of extended cold, resulting in widespread weal breakout and even fainting spells. There are less common forms of urticaria that result from exposure to sunlight, warmth, external contact or absorption of chemical elements from plants, and further external causes.

Differential Diagnosis (Other conditions with similar appearance)
Atopic Dermatitis
Contact Dermatitis, Allergic
Drug eruptions
Erythema multiforme
Henoch-Schonlein Purpura (Anaphylactoid Purpura)
Mastocytosis
Pityriasis rosea
Scabies
Urticarial Vasculitis

Diagnosis
Key points
In most cases, there is no need for investigation.
Testing is useful to discount other conditions.

In most cases of urticaria, there is no need for specific investigations. However, the following tests may be helpful to discount other conditions: full blood count to identify allergy or parasitic infestation or low white blood count from systemic lupus erythematosus, thyroid antibodies testing to determine autoimmune condition, skin prick or blood testing for specific allergy, autologous serum skin prick testing, complement tests in case of angiodema, and skin biopsy to identify Vasculitis.

Treatment
Key points
Treatment depends on the type of urticaria, its severity and how long it has been present.
Oral antihistamines tend to be the most effective treatment, both in sedative and non-sedative form, or a combination of several types.
Other medications and treatments are effective where antihistamines are failing.
There are general preventative lifestyle choices that can help alleviate the causes and breakout of weals.

Treatment depends on the type of urticaria, its severity and how long it has been present. Oral Antihistamines control wealing and itching for the majority of patients with Urticaria. They do not affect the underlying cause of the rash. Antihistamines may need to be taken on a varying basis until the Urticaria disappears. Non-sedating Antihistamines include loratidine, desloratidine, fexofenadine, levocetirizine, and cetirizine. Cetirizine is the quickest acting of these medications, and desloratidine is the most long-lasting. Conventional antihistamines such as chlorpheniramine or promethazine may be preferred at night as they tend to have a sedative effect. Hydroxyzine or diphenhydramine may be taken during the day and in some people they appear more effective than newer, non-sedating Antihistamines. Response and tolerance varies, so if the first antihistamine is not effective, consult your doctor. You may need to increase the dose, or use a different drug. Usually any sedative effect wears off in a week or so. Sometimes a combination of antihistamines works better than a single type alone.

Other treatments may be tried for urticaria that fails to clear with antihistamines. Off-license addition of H2 blockers, such as cimetidine or ranitidine, can also reduce Urticaria. Oral sterioids (prednisone) in moderate dose for a few days are useful for severe acute urticaria, but rarely recommended long term because of serious adverse effects. Tricyclic medications such as amitriptyline, nortriptyline and doxepin are thought to help, as well as antileukotriene agents, such as montelukast. Ultraviolet radiation treatment such as narrowband UVB and PUVA also reduces some wealing. Antibiotics, dapsone, sulfasalazine and antifungal agents are used to clear underlying infection or for their anti-inflammatory action. Immunosuppressive medications such as ciclosporin, Methotrexate, plasmapheresis and intravenous immunoglobulins are reported to help but may have serious side effects. Antifibrinolytic agents (tranexamic acid, androgenetic steroids such as danazol) are mainly used for emergency situations and rare instances.

There are several general lifestyle choices that can help alleviate the causes or breakout of weals. Do not take the medications your doctor has told you to avoid. Minimise use of aspirin and codeine. It is usually safe to take paracetamol to relieve pain. Dietary changes may help. Some urticaria is aggravated by certain fruits, additives, and other food chemicals. Whether or not these need to be avoided can be determined by appropriate food challenge tests. Avoid alcohol, as it causes the surface blood vessels to dilate. Try not to overheat. Cool the affected area with a fan, cold flannel, ice pack or soothing moisturising lotion.