I. Etiology
The cause of acute urticaria can often be found, but the cause of chronic urticaria is more difficult to define. The etiology is usually divided into exogenous and endogenous.
Exogenous factors are mostly temporary and include physical stimuli (friction, pressure, cold, heat, sunlight exposure, etc.), food (animal proteins such as fish, shrimp, crab, shellfish, eggs, etc., plant or fruit such as lemon, mango, plum, apricot, strawberry, pecan, cocoa, garlic, tomato, etc., spoiled food and food additives), drugs (immune-mediated such as penicillin, sulfonamides, serum preparations, various vaccines, or non-immune-mediated mast cell releasing agents such as morphine, codeine, aspirin, etc.), implants (artificial joints, anastomoses, heart valves, orthopedic plates, steel nails, and gynecological birth control devices, etc.), and exercise.
Endogenous factors are mostly persistent and include mast cell hypersensitivity to IgE, chronic occult infections (bacterial, fungal, viral, and parasitic infections, e.g., Helicobacter pylori infection may be important in a minority of patients), exertion or stress, autoimmunity against IgE or high-affinity IgE receptors, and chronic diseases such as rheumatic fever, systemic lupus erythematosus, thyroid disease, lymphoma leukemia, inflammatory bowel disease, etc. In particular, chronic urticaria is rarely caused by allergen-mediated causes.
Diagnosis and differential diagnosis
1. History and physical examination: A thorough history and physical examination should be taken, including possible triggering and relieving factors, duration of the disease, frequency of attacks, duration of lesions, diurnal pattern of attacks, size and number of clusters, shape and distribution of clusters, whether angioedema is combined, degree of accompanying itching or pain, whether there is pigmentation after fading, previous personal or family history of allergy, history of infection, history of visceral disease, history of trauma, history of surgery, history of use of drugs, and history of allergy. History of trauma, surgery, medication history, psychological and mental conditions, menstrual history, lifestyle, work and living environment, and response to previous treatment, etc.
2, laboratory tests: usually urticaria does not require additional tests. Acute patients can be checked for routine blood tests to see if the onset is related to infection or allergy.
In chronic patients with severe disease, long duration of disease or poor response to conventional doses of antihistamines, relevant tests can be considered, such as routine blood, eggs, liver and kidney function, immunoglobulins, erythrocyte sedimentation rate, C-reactive protein, complement and various autoantibodies. Allergen screening, food diary, autologous serum skin test (ASST) and H. pylori infection identification can be performed if necessary to exclude and determine the role of relevant factors in the pathogenesis.
III. Treatment
1. Patient education: Patients with urticaria, especially chronic urticaria, should be educated. The etiology of the disease is unknown, the disease is recurrent and prolonged, except for a very small number of complications with respiratory or other systemic symptoms, the vast majority are benign in nature.
2, etiological treatment: the elimination of causative or suspected causes is conducive to the natural regression of urticaria. Treatment is mainly considered from the following aspects.
① Detailed medical history is the most important way to discover possible causes or triggers;
②For patients with induced urticaria, including physical and non-physical urticaria, avoiding the corresponding stimulus or triggering factor can improve the clinical symptoms or even heal spontaneously;
③When drug-induced urticaria is suspected, especially NSAIDs and angiotensin-converting enzyme inhibitors, avoidance (including drugs with similar chemical structures) or substitution with other drugs may be considered;
④ Chronic urticaria clinically suspected to be associated with various infections and/or chronic inflammation may benefit some patients by considering treatment such as anti-infection or inflammation control when other treatments are resistant or ineffective, as appropriate. For example, anti-H. pylori therapy is effective for urticaria associated with H. pylori-associated gastritis;
⑤ For patients with suspected food-related urticaria, patients are encouraged to keep a food diary to look for possible foods and avoid them, especially since some natural food components or certain food additives can cause non-allergic urticaria;
(6) For patients with positive ASST or confirmed presence of autoantibodies against FcεRIa chain or IgE in the body, the addition of immunosuppressants, autologous serum injection therapy or plasma exchange can be considered as appropriate when conventional treatment is ineffective and the condition is severe.
3.Control of symptoms: Drug selection should follow the principles of safety, effectiveness and regular use to improve the quality of life of patients. It is recommended to develop and adjust the treatment plan according to the patient’s condition and response to treatment.
(1) First-line treatment: second-generation non-sedating or hypo-sedating antihistamines are preferred, and the dose is gradually reduced after effective treatment to achieve effective control of the onset of the wind cluster as the standard. To improve the patient’s quality of life, the course of chronic urticaria is generally not less than 1 month, and can be extended to 3 ~ 6 months or longer if necessary. The efficacy of first-generation antihistamines in the treatment of urticaria is definite, but their clinical application is limited by adverse effects such as central sedation and anticholinergic effects.
They can be selected at discretion with attention to contraindications, adverse effects and drug-drug interactions. Commonly used first-generation antihistamines include chlorpheniramine, diphenhydramine, doxepin, ipratropium, ketotifen, etc. Second-generation antihistamines include cetirizine, levocetirizine, loratadine, desloratadine, fexofenadine, avastin, epinastine, epinastine, imipramine, olopatadine, etc.
(2) Second-line treatment: If the symptoms cannot be effectively controlled after 1 to 2 weeks of conventional dosing, considering the differences in response to treatment in different individuals or types of urticaria, you may choose to: change the species or increase the dose by 2 to 4 times with informed consent of the patient; combine with first-generation antihistamines, which can be taken at bedtime to reduce adverse effects; combine with second-generation antihistamines, advocating the combination of drugs of similar structure such as loratadine Combined with desloratadine to improve the anti-inflammatory effect; combined with anti-leukotriene drugs, especially for non-steroidal anti-inflammatory drugs induced urticaria.
(3) Treatment of pregnant and lactating women and children: In principle, antihistamines should be avoided during pregnancy. However, if symptoms recur and seriously affect the patient’s life and work, and antihistamines must be used for treatment, the patient should be informed that there are no absolutely safe and reliable drugs available, and relatively safe and reliable drugs such as loratadine should be chosen on the balance of pros and cons. Most antihistamines can be secreted into breast milk.
In comparison, cetirizine and loratadine are secreted at lower levels in breast milk and may be recommended at the discretion of lactating women, using lower doses if possible. Chlorpheniramine can be secreted through breast milk, reduce the infant’s appetite and cause drowsiness, etc., and should be avoided.
Non-sedating antihistamines are also a first-line choice for the treatment of urticaria in children. The minimum age limits and doses vary significantly among drugs and should be used according to the drug instructions. Likewise, in children who have failed to respond to treatment, first-generation (nighttime use) and second-generation (daytime use) antihistamines can be combined, but with concern for the effects of sedating antihistamines on the child’s learning, etc.
(4) Traditional Chinese medicine: Traditional Chinese medicine has certain efficacy in the treatment of urticaria and requires evidence-based treatment.