What is urticaria?

Urticaria also known as wheals or hives refer to the skin condition where there are raised, well-circumscribed areas of itchy red patches. 
The swelling is caused by histamine, bradykinin, leukotriene C4, prostaglandin D2, and other vasoactive substances from mast cells and basophils in the dermis. which causes blood vessel to leak and localized skin swelling. The itch is caused by the increased amounts of histamines.
Urticaria around loose tissues around the eye and lip will cause angioedema which is deeper swelling. It can affect anyone of any race, gender and age.
Types of Urticaria

1.Acute urticaria refer to hives that lasts less than 6 weeks.

2.Chronic urticaria refer to hives that occurs almost daily that last longer than 6 weeks. Subtypes include Physical urticaria, Urticarial vasculitis and Chronic idiopathic urticaria, including autoimmune urticaria.

3.Episodic urticaria refer to intermittent hives which may last from days to weeks.

Each individual type of urticaria will be discussed in details below.
Acute Urticaria

Causes of acute onset urticaria is undetermined up to 60% of patients. Common causes include drug allergy (e.g. antibiotics, sulfonamides, salicylates, NSAIDs, codeine, antihistamines), viral infections, food allergy, allergy to insect bites, exposure to environmental factors (e.g. pollen, latex, dust, chemicals, plants), stress, exercise and pregnancy (a condition called pruritic urticaria papules and plaques in pregnancy).

Common food that can cause acute urticaria include nuts, eggs, fresh fruits (especially citrus), chocolates, fish and shellfish, tomatoes, milk and cheese, spices and yeasts. Certain food preservatives and coloring can also cause hives. The urticaria rash may begin within minutes to hours post ingestion depending on the food absorption rate.
Usually acute allergic reaction is mild with red itchy rash on the body. However in a small group of patients, it can lead to anaphylaxis shock presenting within minutes after exposure. Anaphylaxis presents with urticaria, angioedema, a tight chest, wheezing, faintness and collapse. Patients should be resuscitated immediately and advised to carry an EpiPen which contains epinephrine on standby if it occurs.
Investigation: Skin Prick test and blood RAST test may sometimes able to identify the allergen that cause the urticaria.
Treatment: Avoid the precipitating factor that can trigger urticaria. If urticaria occur, oral antihistamines will help relieve it. Steroids can reduce inflammation associated with urticaria and hence it is sometimes prescribed.In patients with serious anaphylaxis reaction, EpiPen is lifesaving.
Chronic Urticaria

Physical Urticaria

Physical urticaria refers to urticaria caused by external physical stimulus. It often does not last more than 1 hour except for delayed pressure urticaria that can last more than 1 day. Delayed pressure urticaria occurs when there is perpendicular pressure applied to the skin and may be associated with fatigue and bone pain. 

Dermographism refer to immediate itchy urticaria caused by stroking of the skin (drawing/writing on skin). Heat contact urticaria refers to wheals that occur skin contacts with heat. Cold urticaria occur when skin is exposed to cooling.
Cholinergic urticaria results from sweating, emotions, hot weather. It especially occurs after exercise resulting in multiple red itchy spots that occur on the skin.
Vibratory urticaria occurs due to a vibrating stimulus on the skin. Solar Urticaria occurs after exposure to UV rays or lights. Aquagenic urticaria occurs when skin is wet.
Diagnosis: is made by its typical occurrence after exposure to certain stimulus. Physical stimulus challenge test can be done to confirm diagnosis. Cryoglobulins is present in patients with cold urticaria.
Treatment: Physical urticaria is long standing because each time after a stimulus it will last from days to weeks. General measures include identify the stimulus that trigger urticaria and avoid it. Oral antihistamines can be given to reduce the itch. Steroids may be more useful in chronic cases as compared with acute cases. Steroids should be given the minimal dose and shortest period possible to reduce its side effects. 
Urticarial Vasculitis

Urticarial vasculitis refer vasculitis (inflamed blood vessels) presenting with inflamed red patches/wheals which may sometimes cause itch or pain. It may look just like urticaria. Bruising and petechiae (small bleeding spots) may also occur.  Angioedema occur in 30% of patients and joint pain in 50% of patients.
Causes of urticarial vasculitis include connective tissue disorder (SLE, Sjogren syndrome), leukemia, Immunoglobulin disorders, Hepatitis B &C and sometimes drug induced. Most of the time the cause is idiopathic unknown cause.
Diagnosis: is made by skin biopsy to confirm the histological findings of urticarial vasculitis. Blood tests like complement studies, autoimmune markers, hepatitis screen will help differentiate the cause of urticaria vasculitis.  
Treatment: is dependent on the cause of the vasculitis. Antihistamines seldom improves the condition much although it helps control itch. NSAIDs can be given to relief pain. Long term control of this longstanding conditions may require long term treatment with drugs like dapsone, hydroxychloroquine, colchicine and prednisolone. In resistant cases, immune-suppressive drugs like methotrexate, ciclosporin and cyclophosphamide may be used. 
Chronic Idiopathic Urticaria

When urticaria vasculitis and physical urticaria has been ruled out then the patient’s longstanding urticaria is called chronic idiopathic urticaria (undetermined cause). Usually the wheals will last less than a day and the itch intensity varies. The average duration of chronic idiopathic urticaria is about 1-2 years and its clinical course consist of periods of flare and remission.
Investigations: Blood tests include thyroid function test to exclude thyroid disorders and full blood count to rule out high eosinophil counts due allergy or parasitic infestation and low white blood count from systemic lupus erythematosus (SLE).
Skin prick test and RAST allergy blood tests are not useful.

Treatment: General measure include avoiding any triggers that may be attributed to the flare. Oral antihistamines to reduce the flare and itch. Montelukast 10 mg daily can be added in addition to the antihistamines to ease the urticaria.

Topical steroids are generally not helpful. Oral steroids can be given in lowest dose and tapering dose for the shortest amount of time to minimize its side effects. Long term oral steroids should be avoided as it increases risk of diabetes, hypertension, gastritis, cataracts, weakens immune system and increases osteoporosis risk.

Immune suppressants like ciclosporin with dosage 4-6 mg/kg/day for up to 3 months can be given if urticaria is resistant to antihistamines and short course of steroids.
Autoimmune urticaria

Approximately 50% of all chronic urticaria is caused by autoimmune urticaria which produce antibodies that trigger mast cells activation.  Autoimmune disorders like SLE, rheumatoid arthritis, polymyositis, thyroid autoimmunity, and other connective tissue diseases are the common causes.
Investigation: Autologous Serum Skin Test (ASST) is a useful screening test. The patient’s serum which is obtained when patient has an urticaria flare is re-injected intradermally back into the patient’s uninvolved skin.  A positive wheal and flare response at 30 minutes suggests the presence of anti-FcєR1 or anti-IgE autoantibodies compared with controls.
Treatment: General measure include avoiding any triggers that may be attributed to the flare. Oral antihistamines to reduce the flare and itch. Montelukast 10 mg daily can be added in addition to the antihistamines to ease the urticaria.
Topical steroids are generally not helpful. Oral steroids can be given in lowest dose and tapering dose for the shortest amount of time to minimize its side effects. Long term oral steroids should be avoided as it increases risk of diabetes, hypertension, gastritis, cataracts, weakens immune system and increases osteoporosis risk.

Immune suppressants like cyclosporin with dosage 4-6 mg/kg/day for up to 3 months can be given if urticaria is resistant to antihistamines and short course of steroids.
Schnitzler’s syndrome

Schnitzler’s syndrome presents with chronic long standing urticaria and IgM gammopathy which does not respond to antihistamines. Patients may also have intermittent fever, joint and bone pain.
Investigations: Serum protein electrophoresis may show an IgM gammopathy. Blood ESR levels will also be raised. X-ray of the long bones and axial skeleton may show hyperostosis (excessive growth of bones).
Treatment: As this syndrome does not respond to antihistamines, the most effective treatment is oral steroids. Currently there is no other specific guidelines for treatment. 
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