Chronic Urticaria: Mechanisms, Diagnosis, and Treatment

What Is Chronic Urticaria?

Chronic urticaria is defined by the presence of wheals (raised, reddish, and itchy plaques) and/or angioedema in a recurrent fashion for more than 6 weeks. The condition is divided into chronic spontaneous urticaria (CSU) — without an identifiable trigger — and chronic inducible urticaria — triggered by specific physical stimuli.

CSU is the most common form and affects 0.5-1% of the population. Each individual wheal lasts less than 24 hours and resolves without marks, but new lesions appear continuously. The disease is predominantly female (2:1), with peak incidence between 20-40 years.

Chronic urticaria is not an allergic disease in the classic sense. In up to 50% of cases, autoimmune mechanisms are involved, with autoantibodies against the IgE receptor or against IgE itself on the mast cell surface. This understanding has revolutionized treatment with the advent of biologic therapies.

Pathophysiology

The central event in chronic urticaria is the degranulation of cutaneous mast cells. Mast cells release preformed mediators (histamine, tryptase, TNF-α) and newly synthesized ones (leukotrienes, prostaglandins, cytokines). Histamine causes vasodilation, increased vascular permeability, and stimulation of pruritogenic nerve endings.

In type I autoimmune CSU, IgE autoantibodies against autoantigens (such as thyroperoxidase, IL-24) bind mast cells and chronically activate them. In type IIb autoimmune CSU, IgG autoantibodies bind directly to the high-affinity IgE receptor (FcεRI) or to receptor-bound IgE, activating mast cells independently of allergens.

Beyond autoimmune mechanisms, complement activation, coagulation, and stress may also drive mast cell activation. The extrinsic coagulation pathway, through thrombin generation, can activate mast cells via PAR-1 receptors. This explains why coagulation markers such as D-dimer may be elevated in active CSU.

Symptoms

Chronic urticaria manifests as wheals (raised, erythematous, itchy, and migratory lesions) and/or angioedema (deep swelling of skin and mucosa, most common on lips, eyelids, and extremities). Itching is the most disabling symptom, frequently worsening at night.

Diagnosis

The diagnosis of chronic urticaria is clinical. Extensive laboratory investigation is unnecessary in most cases and is not routinely recommended by current guidelines. The main goal is to exclude differential diagnoses and identify the subtype (spontaneous vs. inducible, autoimmune vs. non-autoimmune).

Differential Diagnosis

Chronic spontaneous urticaria is the most common diagnosis, but serious conditions such as hereditary angioedema and urticarial vasculitis must be excluded, as they have distinct treatment and prognosis.

Hereditary Angioedema: An Emergency That Cannot Be Missed

Hereditary angioedema (HAE) is a rare, autosomal-dominant disease caused by C1-esterase inhibitor deficiency or dysfunction. Unlike chronic urticaria, HAE causes non-itchy swelling without urticaria — typically of lips, tongue, face, extremities, and gastrointestinal tract (severe abdominal pain in visceral attacks). Laryngeal angioedema is the life-threatening complication and requires immediate access to icatibant or C1-inhibitor concentrate.

Differential diagnosis is crucial because HAE does not respond to antihistamines, corticosteroids, or epinephrine — treatments that work in conventional urticaria. Measuring C4 (generally low during and between attacks in types I and II) along with antigenic and functional C1-inhibitor establishes the diagnosis. Family history is positive in 75% of cases.

Urticarial Vasculitis: When Urticaria Leaves Marks

Urticarial vasculitis (UV) is a small-vessel vasculitis that presents with urticarial lesions but with features distinct from CSU: papules persist more than 24 hours in the same location, cause burning more than itching, and leave ecchymosis or hyperpigmentation on resolution. It may be associated with lupus, Sjögren syndrome, or be idiopathic.

Skin biopsy with direct immunofluorescence is mandatory for UV diagnosis, showing leukocytoclastic vasculitis with immunoglobulin and complement deposits. Workup for associated systemic autoimmune disease includes ANA, complement (C3, C4), anti-DNA, and cryoglobulins. Treatment differs from CSU and may require immunosuppressants.

Mastocytosis: When Tryptase Is Elevated

Systemic mastocytosis results from abnormal mast cell accumulation in organs such as skin, bone marrow, and liver. The isolated cutaneous form (urticaria pigmentosa) presents with brownish macules and papules that wheal on rubbing (positive Darier sign). Systemic episodes include flushing, hypotension, dyspnea, and diarrhea.

Elevated baseline serum tryptase (above 20 ng/mL) suggests systemic mastocytosis and mandates hematology workup, including bone marrow biopsy. In CSU, tryptase may be moderately elevated during flares but not at baseline. The acupuncture physician recognizes these warning signs for appropriate referral.

Treatment

Treatment follows a stepwise algorithm well defined by international guidelines. The goal is complete symptom control (UAS7 = 0) with minimal adverse effects. Second-generation antihistamines are first line, followed by dose escalation and biologic therapy.

Acupuncture as Treatment

Acupuncture has been investigated in chronic urticaria with a focus on possible immunomodulatory and antipruritic effects. Preclinical and experimental studies suggest that acupuncture may influence mast cell degranulation, IgE levels, and the Th1/Th2 balance — but these findings are mostly hypothetical, based on experimental models, and still need to be confirmed in well-designed clinical trials in CSU.

Acupuncture has also been proposed to help control itching through central mechanisms — a hypothesis based on studies in other pruritic conditions — and stress modulation, a recognized aggravating factor, may indirectly contribute to symptom control.

In clinical practice, acupuncture may be a complementary therapy — especially in mild to moderate CSU, as adjunct to antihistamines, or for patients seeking to reduce medication doses. It does not replace stepwise treatment with antihistamines and biologics.

Prognosis

Chronic spontaneous urticaria has a variable course. Roughly 30-50% of patients achieve spontaneous remission within 1-3 years and 80% within 5 years. However, 10-20% may have persistent disease beyond 5 years. Worse prognosis is associated with concomitant angioedema, autoimmune component, and greater initial severity.

With current therapeutic options — especially omalizumab — most patients achieve satisfactory symptom control. Quality of life can be maintained close to normal during treatment, even before the disease enters remission.

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