Types of Urticaria and Hives
Urticaria, which is also known as hives or wheals, occurs in all races and affects approximately 15-20% of the general population at one time. It is the most commonly seen skin disorder in the emergency department and one that should be attended to emergently since it can progress to life threatening angioedema and anaphylaxis. Symptoms of urticaria can develop within minutes to hours of coming in contact with the causative allergen. These symptoms include intensely pruritic (itchy), elevated, well-circumscribed papules and plaques (swellings) with localized edema (swelling).
This localized edema results in lesions which are palpable lesion. The lesions of urticaria are erythematous (red) though they can be flesh colored in dark skinned people. Urticarial lesions are also non-scaly and they blanch completely when pressure is applied to them.
Though they are usually separated by normal skin, urticarial lesions can coalesce and cover large areas of the body. They are also migratory since they can move from one part of the body to another and involve the skin on any part of the body. These lesion can take on many forms such as linear, circular, or arcuate (serpiginous).
Dermographism, which is the development of urticarial lesions when pressure is applied to the skin, may be positive in patients with the physical urticarias and also in 5% of normal people.
WHAT ARE THE DIFFERENT TYPES OF URTICARIA?
Urticaria can either be classified acute urticaria or chronic urticaria depending on the duration of the lesions...
1. Acute urticaria
Acute urticaria is usually a self-limiting illness since the transient lesions usually resolve within 24 hours though they may recur for up to 6 weeks. It can occur in all age groups and its incidence is equal in both men and women. Acute urticaria can develop because of physical contact with allergens such as latex, inhalation of allergens in molds, ingestion of allergens in shellfish and intravenous administration of allergens in radio-contrast dye. The cause of acute urticaria are usually identified in around 50% of patients. Most cases of acute urticaria respond well to treatment with histamine receptor blockers and patients have complete resolution of symptoms within a week.
2. Chronic urticaria
Chronic urticaria lasts for more than 6 weeks. Chronic urticaria commonly occurs in the fourth and fifth decades and affects fewer men than women since over 60% of patients with chronic urticaria are women. The causes of chronic urticaria are identified in less than 20% of patients despite exhaustive investigations. Though it is estimated that almost 50% of chronic urticaria is due to autoimmune diseases such as systemic lupus erythematosus (SLE), Sjogren's syndrome, rheumatoid arthritis, and autoimmune thyroiditis, most cases are thought to be idiopathic. Chronic urticaria can be challenging to treat since its response to treatment depends on the identifying and treating the underlying cause if present.
Urticaria can also be classified according to the type of
immune reaction in the following manner:
1. Acute immunoglobulin E (IgE) mediated urticaria
Skin lesions arising due to IgE mediated reactions, which is a type 1 allergic response, last for less than 24 hours and when they resolve, they leave normal skin. These lesions are frequently migratory as they move from one part of the body to another and can affect skin on any part of the body. Acute IgE mediated urticarial lesions can occur alone or they can be associated with the potentially fatal angioedema or anaphylactic shock.
2. Urticarial vasculitis
The lesions of urticarial vasculitis, which is a type 2 allergic response, develop when immunoglobulins, complement, and fibrin are deposited around blood vessels. These lesions last longer than the acute immunoglobulin E (IgE) mediated urticaria skin lesions often lasting for more than than 36-48 hours. In addition to being itchy, these lesions are also painful and they may be ecchymotic (bruise-like). They also do not blanch in contrast to those of acute IgE mediated urticaria and they may be associated vesicles and signs of cutaneous vasculitis. On resolving, the lesions of urticarial vasculitis leave hyperpigmented (darker than surrounding skin) lesions which are also purpuric or ecchymotic. A skin biopsy can be done for patients suspected to have urticarial vasculitis and it usually reveals leukocytoclastic vasculitis. Treatment of vasculitic urticaria involves medications such as methotrexate, colchicine, dapsone, indomethacin, and hydroxychloroquine.
3. Autoimmune urticaria
Autoimmune urticaria, which is a type 3 allergic response, is associated with autoimmune diseases such as systemic lupus erythematosus and myeloma. Immune mediated mast cell activation occurs when antibodies to IgE receptors on mast cells bind to the mast cells and cause them to release the vasoactive histamine.
4. Chemical induced urticaria
Chemical induced urticaria is a non-immunoglobulin E (IgE) mediated urticaria which is caused by drugs like opioids, vecuronium, succinylcholine, vancomycin, and radiocontrast media. Opioids like morphine, codeine, and pethidine as well as antibiotics like vancomycin cause direct mast cells degranulation and the release of histamine. Other drugs such as aspirin can cause mast cell degranulation by inhibiting the enzyme cyclo-oxygenase. Angiotensin converting enzyme (ACE) inhibitors cause urticaria by increasing the levels of bradykinin.
5. Cholinergic urticaria
This can be triggered by physical exercise, emotional stress as well as exposure to heat. These patients usually have other symptoms of cholinergic stimulation such as lacrimation (tearing), salivation (excessive production of salive), and diarrhea.
6. Physical urticarias
This can be triggered by cold temperatures, high temperatures, contact with water, exposure to sunlight, vibration and pressure which can be immediate pressure or delayed pressure urticaria.
7. Systemic mastocytosis or urticaria pigmentosa.
Systemic mastocytosis or urticaria pigmentosa is characterized by small pigmented papules (swellings) which are transformed into wheals by stroking. A skin biopsy can serum tryptase levels can be done to help confirm the diagnosis.
The urticaria treatment does not depend on the cause of the urticaria and it begins in the pre-hospital setting where the patient or the people with the patient should ensure that they get to the hospital in a timely manner since urticaria can progress to life threatening angioedema and anaphylactic shock.
If the patient has symptoms suggesting associated angioedema or anaphylaxi such as voice changes or hoarseness of voice, stridor or wheezing, light headedness or fainting episodes, they should be given an injection of 0.3 to 0.5 mg of epinephrine (adrenaline) in the muscle, diphenhydramine 50 mg in the muscle or 25 mg intravenously and nebulized with albuterol before they get to the hospital. They can also be given oxygen and intravenous crystalloids.