bubble_chart Overview

Urticaria, commonly known as wheal, is a common skin disease. It is caused by various factors that lead to temporary inflammatory congestion of the skin's mucous membrane blood vessels and the leakage of a large amount of fluid, resulting in localized edematous damage. It rapidly appears and subsides, accompanied by intense itching. Symptoms may include fever, abdominal pain, diarrhea, or other systemic manifestations. It can be classified into acute urticaria, chronic urticaria, angioneurotic edema, and papular urticaria.

bubble_chart Etiology

Approximately 3/4 of patients cannot identify the cause, especially in chronic urticaria. It can be triggered by various endogenous or exogenous complex factors. Common causes can be summarized as:

1. Medications Many drugs often induce this condition, such as penicillin, furazolidone, and sulfonamides. Serums, vaccines, etc., can cause it through allergic reactions, while drugs like morphine, codeine, and atropine can directly stimulate mast cells to release histamine.

2. Food Common allergens include foods containing specific proteins, such as fish, shrimp, crab, eggs, and milk.

3. Infections Bacterial infections, viral infections, fungal infections, and parasites like Chinese Taxillus Herb. Insect bites from mites, fleas, bedbugs, etc.

4. Inhalants Various substances like Mongolian snakegourd root, dust, etc.

5. Physical and chemical factors Physical and mechanical stimuli such as cold, heat, sunlight, friction, and pressure, or exposure to certain chemicals.

6. Genetic factors For example, familial cold urticaria.

7. Psychological factors and endocrine changes Stress, emotional agitation, menstruation, menopause, pregnancy, etc.

8. Internal diseases Lymphoma, cancer, hyperthyroidism, Bi disease and rheumatoid arthritis, SLE, hyperlipidemia, cholecystitis, nephritis, liver disease, diabetes, etc.

bubble_chart Pathogenesis

The mechanism of wheal occurrence can be divided into two categories: allergic reactions and non-allergic reactions.

1. Allergic Type: Primarily Type I, where antigens and IgE antibodies act on mast cells and basophils, causing their granules to degranulate and release a series of chemical mediators (such as histamine and histamine-like substances, including slow-reacting substances, 5-hydroxytryptamine, bradykinin and kinins, prostaglandins, heparin, etc.). This leads to capillary dilation, increased permeability, smooth muscle spasms, and increased glandular secretion, resulting in symptoms in the skin, mucous membranes, digestive tract, and respiratory tract.

Some cases belong to Type II, where antigen-antibody complexes activate complement, forming anaphylatoxins such as C₃ and C₅, and releasing chemotactic factors that attract neutrophils to release lysosomal enzymes. These stimulate mast cells to release histamine and histamine-like substances, causing conditions such as urticaria induced by furazolidone or injection of heterologous serum proteins.

2. Non-Allergic Type: Certain biological, chemical, and physical factors can directly act on mast cells and basophils, causing them to degranulate and trigger symptoms. Increased excitability of cholinergic nerve endings in the skin leads to the release of large amounts of acetylcholine, which can directly act on capillaries, causing dilation and increased permeability. It can also act on mast cells, prompting the release of mediators like histamine.

Kinin and bradykinin also cause capillary dilation and increased permeability, which are associated with conditions like cold urticaria, dermatographism, and pressure urticaria. 5-hydroxytryptamine and prostaglandin E may be related to urticaria, while slow-reacting substances can induce asthma, though their connection to urticaria has not been confirmed.

bubble_chart Clinical Manifestations

Urticaria (wheals) appear rapidly, and a few minutes before their appearance, the affected area often feels itchy or tingling. Some patients may experience systemic symptoms such as loss of appetite, general malaise, headache, or fever within a few hours or one to two days after the onset of urticaria.

Urticaria presents as flat, red, or pale yellowish edematous patches with red halos at the edges. Sometimes, urticaria forms ring-shaped lesions, known as annular urticaria. When several adjacent ring-shaped lesions merge or fuse, they may form a map-like pattern, referred to as geographic urticaria. Occasionally, petechiae may appear at the center of the lesions, known as hemorrhagic urticaria, which can be accompanied by bleeding in the kidneys or gastrointestinal tract. When vesicles appear in urticaria, it is called vesicular urticaria. If bullae are present, it is termed bullous urticaria. Sometimes, vesicles or bullae develop on seemingly normal skin but often with a red halo. This type of urticaria is more common in children.

Urticaria typically resolves naturally within one to two hours or up to one to two days, but new lesions often appear elsewhere. Areas where urticaria has disappeared usually do not develop new lesions within 24 hours. After urticaria subsides, the skin returns to normal, though temporary pigmented spots may remain, known as pigmented urticaria. The size and number of urticaria lesions vary and can appear on any part of the skin or mucous membranes. Urticaria causes intense itching, a stinging or burning sensation, though the severity varies among individuals. Severe cases may present with systemic symptoms like headache and fever. In acute urticaria, fever can reach around 40°C, and blood pressure may drop, leading to syncope or shock, requiring prompt treatment. Most patients, however, only experience itchy urticaria without other symptoms.

The course of urticaria is unpredictable. Some patients may develop rashes several times a day, which subside after a few days, one to two weeks, or several weeks—this is termed acute urticaria. However, many patients experience daily rashes or recurrent episodes that worsen, improve, or disappear intermittently, lasting for months or even years. These cases are classified as chronic urticaria or special types of urticaria.

1. Acute urticaria: Often manifests suddenly with generalized cutaneous pruritic wheals and rashes, sometimes accompanied by high fever. In severe cases, blood pressure may drop, leading to shock. The condition typically resolves naturally within one to two weeks, but active treatment is recommended.

2. Chronic urticaria: Characterized by recurrent wheals lasting one to three months or even years. The severity and presentation vary widely among individuals. Some may develop dermatographic urticaria, often occurring at sites of pressure like waistbands. Wheals triggered by cold water or wind are called cold urticaria, typically presenting as paroxysmal small wheals with red halos, which can spread widely. These patients are often sensitive to acetylcholine, and a positive intradermal test with 0.01 mg of acetyl-methylcholine (resulting in a 1–1.5 cm wheal within 10 minutes) confirms the diagnosis. The condition may persist for months to years.

3. Angioedema: Also known as giant urticaria, it results from reduced or inactive levels of C₁ esterase inhibitor in the blood and tissues. It involves small vessels in the deep dermis and subcutaneous tissue, where mediators like histamine cause vasodilation, increased permeability, and fluid leakage into loose tissues, leading to localized edema. It is episodic, recurrent, and non-pitting, usually non-pruritic. Lesions may appear suddenly as skin-colored swelling on the lips, face, or limbs, or as white swelling due to severe edema compressing superficial capillaries. The borders are indistinct, and the area feels tense with minimal itching. These lesions typically resolve within days but may recur. Some patients may develop multiple lesions, usually without systemic symptoms. Rarely, swelling in the throat can cause asphyxiation, which may be fatal if not managed promptly.

4. Papular urticaria is a common skin disease in children, but it can also be seen in adults. It tends to recur during the spring and autumn seasons. This disease is named based on its symptomatic characteristics. In fact, some patients with this condition actually have insect bite reactions. It is particularly an exogenous allergic reaction caused by bites from arthropods, which is a delayed response taking about 10 days. Subsequent bites then trigger the onset of rashes, and repeated bites can lead to desensitization.

The rash consists of spindle-shaped, peanut-sized red wheal-like lesions that can be scattered or clustered, may have pseudopodia or blisters, and become wheal-like swellings after scratching. New and old rashes often coexist, resolving in 1–2 weeks and leaving temporary pigmentation. It frequently recurs, with intense cutaneous pruritus but no systemic symptoms, and may present with localized lymphadenopathy.

bubble_chart Diagnosis

The diagnosis of wheal lesions is not difficult. A thorough medical history and physical examination should be actively pursued to identify the disease cause. It should be differentiated from drug rash, where edematous wheals appear as diffuse, large red patches with indistinct borders. Papular urticaria should be distinguished from chickenpox.

bubble_chart Treatment Measures

Identify the disease cause to primarily eliminate it. Antibiotics are often necessary when there is an infection, and certain foods should be temporarily avoided if allergies are present. Chronic infection foci are often the disease cause of chronic urticaria, but in some patients, the disease cause is difficult to determine or cannot be identified.

1. Internal Medication Antihistamines are important drugs for treating various types of urticaria and can control symptoms in most patients. Although antihistamines do not directly counteract or neutralize histamine nor prevent its release, they compete with histamine and can quickly suppress the formation of wheals. Antihistamines have various side effects, so it is best to choose those with fewer side effects. Workers in high-altitude jobs, drivers, and others should use them cautiously, as drowsiness may lead to accidents. Prolonged use of one antihistamine can easily lead to medicinal property resistance, so switching to another type or alternating or combining medications may be necessary. Children have greater medicinal property resistance than adults, so their relative dosage is also larger.

There are many types of antihistamines. Based on the combination of diseases and clinical manifestations, hydroxyzine (Atarax) can be selected, as it has good sedative and antihistamine effects and is effective for artificial urticaria, cholinergic urticaria, and cold urticaria.

Epinephrine and aminophylline can increase cAMP in mast cells, inhibiting histamine release and rapidly reducing wheals or edema in acute urticaria or giant urticaria. Especially when aminophylline is combined with antihistamines or epinephrine, synergistic effects occur, making it particularly suitable for patients with concurrent asthma or abdominal pain.

6-Aminocaproic acid can be used for cold urticaria and giant urticaria, while atropine, propantheline, or chlorpromazine can be used for cholinergic urticaria.

Calcium preparations can be used for acute urticaria, and drugs like reserpine and adrenobazone can treat chronic urticaria.

Corticosteroids are used for severe acute urticaria and serum urticaria. For pressure urticaria and complement-activated urticaria, lower doses may be used. They are essential for urticaria complicated by anaphylactic shock. Some use a treatment regimen of injections every 3–4 weeks for chronic urticaria.

2. Topical Medication Calamine lotion or zinc oxide lotion can provide temporary relief.

Chinese medicinals are highly effective in treating various types of urticaria. For acute urticaria of the wind-heat type, Jing Fang Tang is used, while for the wind-cold type, Ma Gui Ge Ban Tang is applied. For papular urticaria, Jing Fang Tang is used. Chronic urticaria with acute episodes is treated similarly to acute urticaria; for prolonged cases, treatments like invigorating blood and resolving stasis, strengthening the spleen and dispelling dampness, warming the middle, and tonifying the kidneys are applied based on pattern identification. For heat symptoms, Qing Re Kuan Xiong Tang is used; for wind-cold, Yong An Zhi Yang Fang is prescribed; for spleen deficiency, Stomach Poria Decoction or Ginseng Spleen-Invigorating Pill is given; and for kidney yang deficiency, Golden Chamber Kidney Qi Pill is administered.