What Are the Causes of Urticaria?

Urticaria is commonly called rubella. It is a localized edema reaction due to the expansion of skin and mucosal small blood vessels and increased permeability. It usually subsides within 2 to 24 hours, but new rashes occur repeatedly. The course of the disease is delayed for several days to several months. More common clinically.

Basic Information

nickname

Rubella block

English name

urticaria

Visiting department

dermatology

Common causes

Allergies, infections, cold and heat, sunlight and other stimuli, mental and genetic factors, etc.

Common symptoms

Itchy skin often precedes red or skin-colored wind masses

Causes of urticaria

The cause of urticaria is very complex, and about three-quarters of patients cannot find the cause, especially chronic urticaria. Common causes are: food and food additives; inhalants; infections; drugs; physical factors such as mechanical stimuli, cold and heat, sunlight; insect bites; mental and endocrine changes; genetic factors.

Clinical manifestations of urticaria

The basic damage is the appearance of wind masses on the skin. Skin itching often occurs first, followed by wind masses, bright red or pale, skin color, and a few patients have edema erythema. Wind masses vary in size and shape, and the onset time is uncertain. The wind mass gradually spread and merged into a piece. Due to the edema of the dermal papilla, the epidermal hair follicle mouth was seen to sag downward. The wind mass lasts for several minutes to several hours, and a few can be extended to a few days to fade without leaving traces. The rash occurs repeatedly in batches and is more common in the evening. Wind masses are common and limited. Angioedema is sometimes combined, and occasionally bullae are formed on the surface of the wind mass.

Some patients may be accompanied by nausea, vomiting, headache, bloating, abdominal pain, diarrhea, and severe patients may also have systemic symptoms such as chest tightness, discomfort, pale skin, accelerated heart rate, weak pulse, decreased blood pressure, and shortness of breath.

Those who have cured the disease in a short time are called acute urticaria. Chronic urticaria is called repeated episodes of at least twice a week for more than 6 consecutive weeks. In addition to the common urticaria mentioned above, there are the following special types of urticaria.

1. Skin scratches urticaria / artificial urticaria

The patient's weaker external mechanical stimulus causes an enhanced physiological response and produces a wind mass on the skin. After the patient scratched, or a tight wind or garter appeared on the tight wind, itching.

2. Delayed skin scratches

Wind scratches and erythema appear on skin scratches 6 to 8 hours after stimulation, and the wind patches last 24 to 48 hours. There are more than one delayed skin lesions, which form small sections or spots along the scratch, the damage is deeper or wider, and even spreads to the sides. Local fever and tenderness.

3. Delayed stress urticaria

The rash occurs 4 to 6 hours after localized skin compression and usually lasts 8 to 12 hours. It is manifested as local deep painful swelling, which may be accompanied by chills, fever, headache, joint pain, general malaise, and mild increase in white blood cell count. Large-scale local swelling is similar to angioedema, which easily occurs in palmar plantar and buttocks with a 24-hour incubation period.

4. Cholinergic urticaria

The rash is characterized by the occurrence of general small wind masses of 1 to 3 mm other than palms and palms, which are obvious around them. Satellite-shaped wind masses are sometimes visible, and only small sparse wind masses with redness or no redness are visible. Sometimes the only symptom is itching without wind. The damage lasts for 30 to 90 minutes, or for hours. Most occur during or shortly after exercise, accompanied by itching, tingling, burning, heat or skin irritation, and can also be induced by heat or emotional stress.

5. Cold urticaria

Can be divided into two kinds of familial and acquired. The former is relatively rare and is autosomal dominant. A delayed reaction occurs half an hour to four hours after being cold. The rash is a non-itchy wind mass with a bluish-purple center surrounded by pale halo. The rash lasts for 24 to 48 hours with a burning sensation and accompanied by fever, Systemic symptoms such as joint pain and increased white blood cell count. The latter is more common. Patients often occur when the temperature drops sharply or after contact with cold water. Within a few minutes, itchy edema and wind masses occur locally, which are more common on the face and hands, but can also be affected in other severe parts. Headaches, flushing of the skin, hypotension, and even fainting can occur.

6. Solar urticaria

After a few minutes of exposure to the skin, itching, erythema, and wind masses quickly develop locally. The wind mass subsided after about 1 to several hours. A rash can be accompanied by chills, fatigue, syncope, and intestinal cramps. These symptoms disappear within hours.

7. Contact urticaria

It is characterized by wind masses and erythema when certain allergens come into contact with the skin. Can be divided into two types of immune mechanisms and non-immune mechanisms. Non-immunity is caused by primary stimulants directly acting on mast cells to release histamine and other substances. Almost all contacts are sick and do not require substance sensitization. The immunity is a type I allergy, which can detect specific IgE antibodies.

In addition, there are less common types of urticaria such as hot urticaria, sports urticaria, tremor urticaria, waterborne urticaria, adrenergic urticaria, and current urticaria.

Urticaria diagnosis

The disease can be diagnosed based on the clinical appearance of wind-like rash. The diagnosis is generally not difficult, but the causes of urticaria are more complicated. It is often difficult to determine the cause of urticaria. Therefore, detailed medical history, detailed physical examination, and related laboratory tests must be used to make the urticaria as clear as possible. the reason.

Urticaria treatment

General treatment

Because of the different causes of urticaria, the treatment effect is also different. Specific treatment measures are as follows:

(1) Remove the cause. Every patient should try to find the cause of the attack and avoid it. If it is caused by infection, the infected lesion should be actively treated. People with drug allergies should stop using allergic drugs; those with food allergies should stop eating this food after finding out allergic foods.

(2) Avoiding predisposing factors such as cold urticaria should keep warm, acetylcholine urticaria reduces exercise, sweating and mood swings, and contact urticaria reduces the chance of exposure.

2. Drug treatment

(1) Antihistamines H receptor antagonists have strong antihistamine and other inflammatory mediator effects, and have a good effect in treating all types of urticaria. Commonly used H ₁ receptor antagonists include diphenhydramine, cyproheptadine, chlorpheniramine, atorvastatin, cetirizine, mizolastine, loratadine, ebastine, azetamine Ting, desloratadine, etc .; when the treatment alone is not effective, two different types of H ₁ receptor antagonists can be used in combination or combined with H ₂ receptor antagonists. The commonly used H ₂ receptor antagonists are cimetidine Titin, ranitidine, famotidine, etc. It is effective for acute, chronic urticaria and cold urticaria. The dose varies from person to person. Doxepin is a tricyclic antidepressant, which has a better effect on chronic urticaria and has less adverse reactions. For patients with urticaria who are not effective with traditional antihistamines, doxepin is a better choice.

(2) Drugs that inhibit the degranulation of mast cells and reduce the release of histamine Misoproterenol sulfate is a beta ₂ adrenal receptor promoter, which can increase the cAMP concentration in the body, thereby inhibiting the mast cell degranulation. Ketotifen By increasing the concentration of cAMP in the body, it inhibits degranulation of mast cells and prevents the release of inflammatory mediators (such as histamine, slow-reacting substances, etc.). Its inhibited. It is stronger and faster than sodium cromoglycate and can be taken orally. Sodium cromoglycate can block the binding of antigen and antibody, and inhibit the release of inflammatory mediators. If combined with glucocorticoids, the dosage of the latter can be reduced and the efficacy can be enhanced. Tranilast can reduce the release of histamine by stabilizing the mast cell membrane.

(3) glucocorticoids

Second-line treatment for urticaria, generally used for severe acute urticaria, urticaria vasculitis, stress urticaria when the antihistamine is ineffective, or when chronic urticaria is severely stimulated, intravenous infusion or oral administration should be avoided for a long time application. The commonly used drugs are as follows: prednisone; triamcinolone; dexamethasone; debao song. In an emergency, hydrocortisone, dexamethasone, or methylprednisolone is used for intravenous drip.

(4) Immunosuppressive agents

When patients with chronic urticaria have an autoimmune foundation and the condition is repeated, and the above treatments cannot achieve satisfactory results, immunosuppressants can be applied. Cyclosporine has a good effect. Globulin, etc. can be tried, and tripterygium also has a certain effect. Due to the high incidence of immunosuppressive side effects, it is generally not recommended for the treatment of urticaria.

In addition, drugs that reduce vascular permeability, such as vitamin C, vitamin P, and calcium, are often used in combination with antihistamines. Caused by infectious factors, you can choose appropriate antibiotic treatment.