|Year : 2015 | Volume
| Issue : 2 | Page : 59-61
Urticaria: An overview
SN Gaur, Gaurav Bhati
Department of Pulmonary Medicine, Vallabhbhai Patel Chest Institute, University of Delhi, New Delhi, India
|Date of Web Publication||9-Mar-2016|
S N Gaur
Department of Pulmonary Medicine, Vallabhbhai Patel Chest Institute, University of Delhi, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gaur S N, Bhati G. Urticaria: An overview
. Indian J Allergy Asthma Immunol 2015;29:59-61
Urticaria (hives or nettle rash) is a vascular reaction of the skin marked by the transient appearance of smooth, slightly elevated papules, or plaques (wheals) of varying size, that are erythematous, blanchable on pressure, occurs often with severe pruritus clinically lasting from few hours to few days, often the lesions are self-limiting and resolve without scarring but may show recurrence over weeks. Angioedema needs to be distinguished from urticaria since angioedema is also similar but more acute, can be more severe and fatal. The development of urticaria is often an isolated event without systemic reaction. Rarely, it can be a prelude to the development of an anaphylactic reaction. Urticaria can be broadly defined as acute, chronic, and intermittent.
Urticaria can be triggered by many substances or situations, and can be associated with identifiable causes, and the method of exposure (i.e., direct contact, oral, inhalation, or intravenous [IV] routes which can be identified by taking a careful history). Urticaria may be confused with a variety of other dermatologic diseases that can be similar in appearance and are pruritic, including atopic dermatitis (eczema), maculopapular drug eruptions, contact dermatitis, insect bites, erythema multiforme, pityriasis rosea, and others, so the role of meticulous history is of prime importance in finding the offending agent in cases of acute urticaria.
| Classification of urticaria|| |
- Immunoglobulin E (IgE) mediated/contact
- Immune complexes
- Physical urticaria
- Drug induced
- Dietary pseudoallergen
- Medical condition
- Urticaria pigmentosa
- Cryopyrin associated
- Periodic syndrome.
| Pathophysiology|| |
Urticaria results from the release of histamine, bradykinin, leukotriene C4, prostaglandin D2, and other vasoactive substances from mast cells and basophils in the dermis. These substances cause extravasation of plasma into the dermis, leading to the urticarial lesion. The intense pruritus of urticaria is a result of histamine released into the dermis.
Histamine is the ligand for two membrane-bound receptors, the H1 and H2 receptors, which are present on many cell types. The activation of the H1 histamine receptors on endothelial and smooth muscle cells leads to increased capillary permeability. The activation of the H2 histamine receptors leads to arteriolar and venule vasodilation. This process is caused by several mechanisms as follows:
- The type I allergic IgE-mediated response of sensitized patients to allergen produce specific IgE against the offending substance, thus a subsequent contact with the relevant allergen either directly on the skin or through mucous membranes may result in urticaria. The reaction is initiated by antigen-mediated IgE immune complexes that bind and cross-link Fc receptors on the surface of mast cells and basophils, thus causing degranulation with histamine release leading to symptoms. Acute urticaria caused by food protein is easy to identify in comparison to finding the offending agent which is a contaminant or ingredient of processed food. Insects, dander, and venoms are common causes of IgE-mediated urticaria
- The type II allergic response is mediated by cytotoxic T cells, causing deposits of immunoglobulins, complement, and fibrin around blood vessels. This leads to urticarial vasculitis
- The type III immune complex disease is associated with systemic lupus erythematosus (SLE) and other autoimmune diseases that cause urticaria.
The causes of nonimmune-mediated urticaria vary from viral and bacterial infections, serum sickness, to transfusion reactions. Urticarial transfusion reactions occur when allergenic substances in the plasma of the donated blood product react with preexisting IgE antibodies in the recipient. Certain drugs as well as radiocontrast agents cause urticaria due to mast cell degranulation through a non-IgE-mediated mechanism.
Food allergy should be considered in acute urticaria in children. Such foods as tree nuts, peanuts, eggs, shellfish, and tomatoes should be considered (the involvement of food additives or preservatives is controversial). Certain natural salicylates in foods and food additives ("E" numbers), including colorings (azo and nonazo dyes), preservatives (sulfites, nitrates, and nitrites), antioxidants (butylated hydroxyanisole and butylate hydroxytoluene,) and aspartame (an artificial sweetener), may cause urticaria.
Specific IgE, tests to the foods are negative, or is not IgE-mediated. In some patients, foods such as egg white, shellfish, and strawberries seem to trigger direct histamine release from mast cells and episodes of urticaria are related to ingestion of these foods. One of the non-IgE-mediated, food-related cause of urticaria is histamine poisoning, for example, "scombroid poisoning," which is due to ingestion of scombroid fish, such as tuna, mackerel, and swordfish, which has not been stored properly and in which bacteria have decarboxylated histidine to produce histamine. Symptoms may begin within 1 h of ingestion in the form of urticaria and gastrointestinal symptoms or a severe form of bronchospasm and hypotension.
Physical urticaria results from various physical factors such as cold, heat, sweating, exercise pressure, sunlight, water, and vibration, all may trigger urticarial reactions in susceptible individuals. The wheals are usually short-lived (less than an hour) in physical urticarias in comparison to those of delayed pressure urticaria, which may take days to disappear. Cold urticaria is usually idiopathic. Patients develop itching, erythema, and urticaria on the part of the body subjected to cold. Prolonged total body exposure to cold can lead to hypotension. Local heat-induced urticaria is rare. Some patients may develop urticaria on exposure to both heat and cold. Generalized heat-induced urticaria or "cholinergic" urticaria is caused by exercise, sweating, and hot showers or baths. The term "cholinergic" is used because sweat glands are innervated by cholinergic nerve fibers. The urticarial lesions are often small and intensely itchy. A very severe form of cholinergic urticaria may cause hypotension.
Solar urticarial is a rare disorder in which urticaria develops on areas of the body which are exposed to sunlight. Itching and urticaria may develop within a few minutes and may progress to angioedema. The symptoms usually resolve in a few hours. Polymorphic light eruption may also cause an itchy rash on sun-exposed skin, but this rash is papular or eczematous; usually starts 6-8 h after sun exposure and lasts for several days. "Aquagenic" urticaria, i.e., development of urticaria on being contact with water and urticaria in response to vibration are a rare form of urticaria. Frequently, more than one type of physical urticaria may occur in a patient, and it may be difficult for the individual to avoid the triggering stimulus/stimuli. The physical urticarias may, therefore, be difficult to treat and may be long lasting.
Drug belongs to class of Cyclo-oxygenase (COX)-inhibitor drugs such as aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) are a common cause. Opiates, including codeine, may trigger direct histamine release from mast cells. Usually, these reactions are not IgE-mediated and specific IgE testing for aspirin, NSAIDs, and opiates are not indicated. Drugs such as angiotensin converting enzyme inhibitors (ACEIs) and statins cause isolated angioedema much more commonly than urticaria. Radiocontrast media and plasma substitutes may also cause urticarial reactions.
A wide variety of different infections can lead to urticaria. Viral infections associated with acute urticaria include acute viral syndromes, hepatitis (A, B, and C), Epstein-Barr virus, and herpes simplex virus. Urticaria has also been reported with chronic parasitic infections. Although sinusitis, cutaneous fungal infections, and Helicobacter pylori infection are known. Recurrent urticaria includes causes such as hepatitis, infectious mononucleosis, H. pylori infection, dental infections, sinusitis, and urinary tract infections.
Urticaria related to medical conditions
Diseases such as SLE and Sjögren's syndrome may be associated with chronic urticaria, a cryoglobulin-related urticaria, or urticarial vasculitis. There is an increased incidence of autoimmune thyroid disease in patients with chronic urticaria, particularly those with histamine releasing autoantibodies - "autoimmune urticaria" There is a rare cyclical form of urticaria, known as autoimmune progesterone urticaria, which occurs 7-10 days premenstrually.
Acute urticaria may develop in relation to a particular stressful event, and it is recognized that financial, personal, or professional stress may all worsen chronic urticaria. The condition itself may be very debilitating and it reduces quality of life.
| Urticaria severity assessment|| |
Visual analog scales can be used to record and compare the degree of itch.
The activity of chronic spontaneous urticaria can be assessed using the UAS7 scoring system. The daily weal/itch scores are added up for 7 days; the maximum score is 42. Morbidity depends on the severity and duration of the condition. Urticaria patients can have as much psychological, social, and occupational distress.
| Diagnosis of urticaria|| |
Urticaria is diagnosed in people with a history of weals that last <24 h with or without angioedema. A family history should be elicited. A thorough physical examination should be undertaken. Skin prick tests and radioallergosorbent tests or CAP fluoroimmunoassay for specific IgE may be requested if a drug, food allergy, or inhalant is suspected in acute urticaria. There are no routine diagnostic tests in chronic spontaneous urticaria apart from complete blood count and C-reactive protein, but investigations may be undertaken if an underlying disorder is suspected. The autologous serum skin test is sometimes carried out in chronic spontaneous urticaria, but its value is uncertain. It is positive if an injection of the patient's serum under the skin causes a red weal. Inducible urticaria is often confirmed by inducing the reaction, for example, scratching the skin in dermographism or applying an ice cube in suspected cold urticaria. Investigations for a systemic condition or autoinflammatory disease should be undertaken in urticaria patients with fever, joint or bone pain, and malaise. Patients with angioedema without weals should be asked if they take ACEI drugs and tested for complement C4; C1-INH levels, function and antibodies; and C1q. Biopsy of urticaria can be nonspecific and difficult to interpret. The pathology shows edema in the dermis and dilated blood vessels, with variable mixed inflammatory infiltrate. Vessel wall damage indicates urticarial vasculitis.
| Treatment|| |
Avoidance of known triggering factors is important, and patients with urticaria should be discouraged from scratching or irritating the skin when active lesions are present. Pressure urticaria may worsen the intensity of the rash; therefore, avoiding tight-fitting clothes may be helpful. The main treatment of all forms of urticaria in adults and in children is with an oral second-generation antihistamine. If the standard dose (e.g., 10 mg for cetirizine) is not effective, the dose can be increased up to 4-fold (e.g., 40 mg cetirizine daily). Although systemic treatment is best avoided during pregnancy and breastfeeding, there have been no reports that second-generation antihistamines cause birth defects. If treatment is required, loratadine and cetirizine are currently preferred. Conventional first-generation antihistamines such as promethazine or chlorpheniramine are no longer preferred for urticaria. An IgE-mediated urticaria may require allergen identification and allergen immunotherapy.
Treatment of refractory urticaria
If nonsedating antihistamines are not effective, a 4-5-day course of oral prednisone (prednisolone) may be warranted in severe acute urticaria. Intramuscular injection of adrenaline (epinephrine) is reserved for life-threatening anaphylaxis or swelling of the throat.
Other treatments that are sometimes used include leukotriene antagonists, tricyclic antidepressants, methotrexate, dapsone, phototherapy, and anti-tumor necrosis factor alpha agents, for example, infliximab, adalimumab, and IV immunoglobulins. Long-term systemic corticosteroids are generally not recommended, as they can have inevitable adverse effects.
The article is to emphasize that a wide variety of causes are there to produce urticaria, and IgE-mediated allergic urticaria is one of them. Treatment should be aimed according to the cause. Allergen immunotherapy is recommended and will be effective only in IgE-mediated allergic urticaria.