Urticaria is a kind of skin rash notable for pale red, raised, itchy bumps. Hives is frequently caused by allergic reactions; however, there are many non-allergic causes. Most cases of hives lasting less than six weeks (acute urticaria) are the result of an allergic trigger. Chronic urticaria (hives lasting longer than six weeks) is rarely due to an allergy. The majority of patients with chronic hives have an unknown (idiopathic) cause. Perhaps as many as 30–40% of patients with chronic idiopathic urticaria will, in fact, have an autoimmune cause. Acute viral infection is another common cause of acute urticaria (viral exanthem). Less common causes of hives include friction, pressure, temperature extremes, exercise, and sunlight
Patients previously designated as having chronic idiopathic urticaria are now divided into 2 groups: 40% to 50% with chronic autoimmune urticaria, and the remainder with chronic idiopathic urticaria. Patients in both groups may have concomitant angioedema (approximately 40%). The autoimmune subgroup has an association with antithyroid antibodies and is caused by IgG antibody to the α subunit of the IgE receptor (35% to 40%), usually reactive with unoccupied IgE receptors, or IgG antibody to IgE (5% to 10%). Complement activation augments histamine secretion by release of C5a. The IgG subclasses that appear to be pathogenic are IgG1, IgG3, and, to a lesser degree, IgG4, but not IgG2. Histology of chronic urticaria (both subtypes) reveals a perivascular non-necrotizing infiltrate of CD4+ lymphocytes consisting of a mixture of TH1 and TH2 subtypes, plus monocytes, neutrophils, eosinophils, and basophils. These cells are recruited as a result of interactions with C5a, cell priming cytokines, chemokines, and adhesion molecules. Suggested therapy for patients with severe disease involves the use of high-dose hydroxyzine or diphenhydramine when nonsedating antihistamines are ineffective, supplemented by H-2 antagonists and leukotriene antagonists. The most severe patient may require protracted treatment with low-dose alternate-day steroid or cyclosporine. Cyclosporine can be steroid-sparing when side effects are encountered or when use of steroids is relatively contraindicated. Careful monitoring of blood pressure, BUN, creatinine, and urinalysis is required.
The traditional definition of chronic urticaria is the presence of hives for more than 6 weeks, and it is usually assumed that hives are present most days of the week. The physically induced urticarias, such as dermatographism, cold urticaria, and cholinergic urticaria, are commonly included in this nonrestrictive definition, but this article will only consider entities that are now considered to be either chronic autoimmune urticaria or chronic idiopathic urticaria. Patients with either of these latter forms of chronic urticaria do not have IgE-mediated hypersensitivity to exogenous allergens as the cause of symptoms and are distinct from the aforementioned physically induced urticarias. Another distinction is pathogenic. Physically induced hives, with the sole exception of delayed-pressure urticaria, have no late-phase response after the initiating urticarial response and therefore have hives lasting no more than 2 hours, whereas individual lesions in patients with chronic autoimmune urticaria or chronic idiopathic urticaria last 4 to 36 hours. The exception, delayed-pressure urticaria, is often seen accompanying either of the 2 types of chronic urticaria, but the diagnosis of chronic urticaria requires the presence of spontaneously occurring hives that are not attributable to a pressure stimulus. It is also recognized that about 40% of patients with either chronic autoimmune or chronic idiopathic urticaria have associated angioedema, most typically involving the face (cheeks and periorbital area), lips, tongue, pharynx, and extremities. Genital swelling is occasionally seen but is more common in men with idiopathic angioedema, whereas laryngeal swelling is seen with C1 inhibitor deficiency, angioedema caused by angiotensin-converting ewnzyme inhibitors, or frank anaphylaxis.
There is a large set of literature dealing with possible causes of chronic urticaria and angioedema that include psychophysiologic reactions, food allergies, adverse reactions to food additives, cutaneous fungal infections (id reactions), and, most recently, hives as a consequence of infection with Helicobacter pylori. Gradually, all of these have been dispelled as myth or erroneous associations, with the exception of H pylori; however, there are data suggesting that the association is a chance occurrence and not a cause-and-effect relationship.
- Acute Acute urticaria usually show up a few minutes after contact with the allergen, and can last a few hours to several weeks. Food allergic reactions often fit in this category.
- Chronic Chronic urticaria refers to hives that persists for 6 weeks or more. There are no visual differences between acute and chronic urticaria. Some of the more severe chronic cases have lasted more than 20 years. A survey indicated that chronic urticaria lasted a year or more in more than 50% of sufferers and 20 years or more in 20% of them.
- Drug-induced type of urticaria Drugs that have caused allergic reactions evidencing as Urticaria comprise: aspirin, penicillin, sulfonamides, anti-convulsants and anti-diabetic drugs such as suphonylurea. Drug-induced Urticaria has been known to affect upon in severe cardio-respiratory failure. The anti-diabetic sulphonylurea glimepiride (trade name Amaryl), in particular, has been authenticated to induce allergic reactions manifesting as Urticaria. Other such instances include dextroamphetamine and clotrimazole.
- Physical urticaria Also medically referred to as Dermatographism or Dermographism, this kind of Urticaria is marked by the appearance of weals or welts on the skin as a result of itching, scratching, or firm stroking of the skin. This is the most common type of physical Urticaria. The skin reaction usually becomes evident soon after the itching and disappears within 30 minutes. Dermographism is a common form of chronic hives. It is also recognised as “skin writing”. Dermatographism is the most common form of a subset of chronic hives, acknowledged as `physical hives`. It happens in some degree in approximately 5 percent of the population. This most common type of Urticaria stands in contrast to the linear reddening that does not itch witnessed in healthy people that are scratched. In most cases the cause is unknown, although it may be preceded by a viral infection, antibiotic therapy, or emotional upset. Dermographism is diagnosed by taking a tongue blade and drawing it over the skin of the arm or back. The hives should develop within 1 to 3 minutes. Unless the skin is highly sensitive and reacts continually, treatment is not needed. Taking antihistamines can reduce the response in cases that are annoying to the patient.
- Pressure or delayed pressure This type of Urticaria can occur right away, precisely after a pressure stimulus or as a deferred response to sustained pressure being enforced to the skin. In the deferred form, the hives only appear after approximately six hours from the initial application of pressure to the skin. Under normal circumstances, these hives are not the same as those witnessed with most Urticarias. Instead, the protrusion in the affected areas is typically more spread out. The hives may last from approximately 8 hours to three days. The source of the pressure on the skin can happen from tight fitted clothing, belts, clothing with tough straps, walking, leaning against an object, standing, sitting on a hard surface, etc. The areas of the body most commonly affected are the hands, feet, the trunk, the buttocks, legs and the face. Although this appears to be very similar to dermatographism, the cardinal difference is that the swelled skin areas do not become visible quickly and tend to last much longer. This form of the skin disease is however, rare.
- Cholinergic or stress This form of Urticaria is fairly widespread and occurs after exercise, sweating, or any activity that leads to a warming of the core body temperature such as warm or hot baths or showers. The hives that are produced are typically smaller than the classic hives. In severe cases, hundreds of tiny red itchy spots appear on the skin with exercising, when the individual is warm or when the individual is experiencing a high level of physical or emotional stress. The red spots manifest rather quickly and remain for approximately 60 to 90 minutes on average. It precisely becomes marked as multiple, small, 2 to 3 mm red hives on the upper trunk and arms, although it can occur from the neck to the thighs. Cholinergic type of Urticaria is known to cause itching, tingling, burning and heating-up of the skin. It is believed that histamine is discharged in response to stimulation by the parasympathetic nervous system. Cholinergic Urticaria is diagnosed by historical measures and also multiplying the hives under certain conditions. Several times, the patient is asked to exercise by jogging instead of riding a stationary bike and the time it takes for hives to develop is noted down. Cholinergic Urticaria can be treated by delimiting the strenuous exercise. This type of Urticaria responds well to a medication named hydroxyzine, which serves as an antihistamine. However, the principal side effect of sleepiness is often not tolerated well. Standing under a shower of hot water may cause a release of histamine throughout the body, exhausting histamine stores and causing a 24-hour refractory period.
- Cold The Cold type of Urticaria or hives are caused by exposure of the skin to extreme cold temperatures. In particular, the hives appear on the skin areas that have been exposed to cold, damp and windy conditions. It comes about in two forms. The rare form is hereditary and becomes evident as hives all over the body 9 to 18 hours after cold exposure. The common form of cold Urticaria demonstrates itself with the rapid onset of hives on the face, neck, or hands after exposure to cold. Cold Urticaria is common and lasts for an average of 5 to 6 years. The population mostly impressed upon is young adults, aged between 18 to 25 years. Many people with cold Urticaria also are stung by dermographism and cholinergic Urticaria. Severe reactions can be witnessed with exposure to cold water. Swimming in cold water is the most commonplace cause of a severe reaction. This can cause a massive discharge of histamine ensuing in low blood pressure, fainting, shock and even loss of life. Cold Urticaria is diagnosed by dabbing an ice cube against the skin of the forearm for 1 to 5 minutes. A distinct hive should develop if a patient is down with cold Urticaria. This is different than the normal redness that can be viewed in people without cold Urticaria. Patients with cold Urticaria needs to learn to protect themselves from a hasty drop in body temperature. Regular antihistamines however are not generally efficacious. The particular antihistamine, cyproheptadine (Periactin) has been found to be of much usefulness. The tricyclic antidepressant doxepin has also been found to be an effective blocking agent of histamine discharge. Finally, a medication named ketotifen, which keeps mast cells from discharging histamine, has also been employed with widespread success.
- Heat This rare form of Urticaria is triggered by the continued application of heat on the skin. Hives begin to germinate within 2 to 5 minutes on the area of the skin that was exposed to heat. The hives however, generally do not last more than an hour.
- Solar This is a form of the disease and is stimulated on areas of the skin that have mostly been exposed to the sun. The skin condition becomes evident within minutes of the sun vulnerability. Although, after the individual is no longer exposed to the sun, the condition starts to weaken out within a few minutes to a few hours and hardly ever lasts longer than 24 hours. Solar Urticaria is classified into 6 different types, depending upon the wavelength of light involved. Since glass absorbs light with a wavelength of 320 nanometre and below, people suffering from solar Urticaria in response to wavelengths of less than 320 nanometre are protected by glass.
- Water This type of Urticaria is also termed as rare and occurs upon contact with water. The response is not temperature dependent and the skin appears similar to cholinergic form of the disease. The appearance of hives is within 1 to 15 minutes of contact with the water and can last from 10 minutes to two hours. The hives that last for 10 to 120 minutes, do not seem to be stimulated by histamine discharge like the other physical hives. Most researchers believe that this condition is actually most delicate skin sensitivity to additives in the water such as chlorine. Water Urticaria is diagnosed by dabbing tap water and distilled water to the skin and observing the gradual response. Aquagenic type of Urticaria is treated with a cream named as capsaicin (Zostrix), that is administered to the chafed skin. This is the same treatment utilised for shingles. Antihistamines are of questionable benefit in this instance, since histamine is not the conducive factor in water Urticaria.
- Vibratory angioedema This is a very rare form of hives that develops in reply to contact with vibration. Angioedema is an intense and more painful form of hives. In vibratory angioedema, symptoms develop within 2 to 5 minutes after contact with vibration and dissolve after approximately 1 hour. Patients with this disorder do not suffer from dermographism or pressure Urticaria. Vibratory angioedema is diagnosed by administering a laboratory vortex to the forearm for 4 minutes. Speedy swelling of the whole forearm extending into the upper arm is also noted down later. The principal treatment of vibratory angioedema is avoidance of vibratory stimulants. Antihistamines have also been proven helpful.
- Exercise-induced anaphylaxis This type of Urticaria is a condition that was first distinguished in 1980. People with this condition experience hives, itchiness, shortage of breath and low blood pressure 5 to 30 minutes after the inception of exercise. These symptoms can progress to shock and even sudden demise. Jogging is the most common type of exercise that causes exercise-induced anaphylaxis. People with exercise-induced anaphylaxis do not get these symptoms after a hot shower, fever, or with fretfulness. This differentiates exercise-induced anaphylaxis from cholinergic Urticaria. Exercise-Induced anaphylaxis sometimes comes about only when someone exercises within 30 minutes of eating particular foods such as wheat and shellfish. For these individuals, exercising alone or eating the injuring food without exercising, produces no symptoms. Such type of Urticaria can be diagnosed by having the patient exercise and then observing the symptoms that germinate. This method must be utilised with caution and only in such a circumstance with the appropriate resuscitative measures ready at hand. Exercise-induced anaphylaxis can be differentiated from cholinergic Urticaria by the hot water immersion test. In this test, the patient is immersed in water at 43 degrees Celsius (109.4 degrees Fahrenheit). Someone with exercise-induced anaphylaxis will not develop hives, while a person with cholinergic Urticaria will develop the characteristic small hives, especially on the neck and chest. The immediate symptoms of this uncanny type of Urticaria are treated with antihistamines, epinephrine and airway support. Taking antihistamines prior to exercise may be effective. A medication referred to as ketotifen, is acknowledged to stabilise mast cells and prevents histamine release and has been effective in treating this hives disorder. Avoiding exercise or foods that cause the mentioned symptoms, is very important. In particular circumstances, tolerance can be brought on by regular exercise, but this must be under secure medical supervision.
- Related conditions Angioedema is similar to urticaria, but in angioedema, the swelling occurs in a lower layer of the dermis than it does in urticaria, as well as in the subcutis. This swelling can occur around the mouth, in the throat, in the abdomen, or in other locations. Urticaria and angioedema sometimes occur together in response to an allergen and is a concern in severe cases as angioedema of the throat can be fatal.
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