Definition and epidemiology
Urticaria (hives) is a cutaneous reaction characterized by transient, pruritic, erythematous or skin-colored wheals (welts) that result from histamine-mediated vasodilation and increased vascular permeability in the superficial dermis. Lesions are classically migratory, meaning individual wheals appear and fade within hours, with the overall episode potentially lasting days to months.
Urticaria is classified by duration:
- Acute urticaria: lasts less than 6 weeks; the most common form, often triggered by infection, food, or drugs
- Chronic urticaria: lasts 6 weeks or longer, occurring most days of the week; subdivided into chronic spontaneous urticaria (CSU) and chronic inducible urticaria (e.g., physical urticarias)
Lifetime prevalence is approximately 15-25%. Acute urticaria is more common in children and young adults, often linked to viral infections. Chronic spontaneous urticaria is more common in adults, with a female predominance (roughly 2:1), and peak incidence in the 30s-50s. Angioedema (deeper dermal/subcutaneous swelling) coexists in up to 40% of chronic urticaria cases.
- Individual urticarial wheals resolve within 24 hours; lesions lasting longer than 24h or leaving bruising suggest urticarial vasculitis
- Histamine release from mast cells/basophils via H1 receptors drives the wheal-flare-itch triad
- Acute urticaria in children is most often triggered by viral infection, not food allergy
- Chronic spontaneous urticaria lasts ≥6 weeks and may have an autoimmune basis (anti-FcεRI or anti-IgE autoantibodies)
- Dermatographism is a common physical urticaria elicited by stroking the skin
- First-line treatment is a second-generation H1 antihistamine; dose can be increased up to fourfold before adding omalizumab or cyclosporine
- Omalizumab is a guideline-endorsed add-on for antihistamine-refractory chronic urticaria
- Angioedema with airway compromise is a medical emergency requiring epinephrine if anaphylaxis is suspected
Etiology and risk factors
Acute urticaria
- Viral upper respiratory infections (most common trigger, especially in children)
- Food allergens (shellfish, nuts, eggs, milk)
- Medications (antibiotics, NSAIDs, opioids)
- Insect stings
- IgE-mediated or direct mast cell degranulation (e.g., opioids, radiocontrast)
Chronic spontaneous urticaria
- Autoimmune mechanism in a significant subset: autoantibodies (IgG) against the high-affinity IgE receptor (FcεRI) or against IgE itself, causing mast cell activation
- Associated with autoimmune thyroid disease (Hashimoto thyroiditis) in some patients
- Often idiopathic despite thorough workup
Chronic inducible urticaria (physical urticarias)
- Dermatographism (stroking/scratching)
- Cold urticaria
- Cholinergic urticaria (heat, exercise, emotional stress — small punctate wheals)
- Solar urticaria
- Delayed pressure urticaria
Risk factors
- Atopic history (asthma, allergic rhinitis, eczema)
- Autoimmune disease
- Recent infection or new medication exposure
- NSAID use (can exacerbate chronic urticaria even without being the primary cause)
Pathophysiology
The central event in urticaria is mast cell and basophil degranulation in the superficial dermis, releasing histamine along with other mediators (leukotrienes, prostaglandins, platelet-activating factor, cytokines).
Histamine binds H1 receptors on dermal blood vessels and sensory nerves, producing the classic triad:
- Vasodilation → erythema
- Increased vascular permeability → dermal edema (the wheal)
- Sensory nerve stimulation → pruritus (itch) via activation of C-fiber nociceptors, often with an axon-reflex flare
Mast cell activation can occur through several pathways:
- IgE-dependent: allergen cross-links IgE bound to FcεRI on mast cells (classic type I hypersensitivity)
- Autoimmune: autoantibodies against FcεRI or IgE directly activate mast cells (seen in roughly 30-50% of chronic spontaneous urticaria)
- Direct/non-immunologic: certain drugs (opioids, vancomycin, radiocontrast) or physical stimuli directly trigger mast cell degranulation without IgE
- Complement-mediated: C3a and C5a (anaphylatoxins) can also trigger mast cell release, relevant in serum sickness and some drug reactions
If edema extends into the deeper dermis and subcutaneous tissue, it manifests as angioedema, which involves fewer sensory nerve endings (hence less itch, more pain/pressure) and can involve mucosal surfaces including the lips, tongue, and airway.
Clinical features
- Pruritic, raised, blanchable wheals with erythematous borders and pale centers
- Lesions are transient: any single wheal resolves within 24 hours, though new ones may continuously form elsewhere
- Size and shape vary widely, from small papules to large confluent plaques
- Dermatographism may be present (linear wheal after firm stroking of skin)
- Angioedema may coexist: deep swelling of lips, eyelids, tongue, hands, or genitalia, typically without itch
- Systemic symptoms (fever, joint pain, lymphadenopathy) are atypical and should raise suspicion for an alternative diagnosis such as urticarial vasculitis or serum sickness
- In cholinergic urticaria: small, punctate wheals with surrounding flare triggered by heat, exercise, or stress
- Red flags warranting urgent evaluation: lesions lasting more than 24 hours, residual bruising/hyperpigmentation, painful rather than itchy lesions, systemic symptoms, or signs of anaphylaxis (airway swelling, wheezing, hypotension)
Diagnosis
Diagnosis is primarily clinical, based on history and physical examination.
Acute urticaria
- No routine laboratory testing is required in most cases
- Identify and address an obvious trigger (recent infection, new drug, specific food) if history suggests one
- Allergy testing (skin prick or specific IgE) only if a specific food/drug trigger is strongly suspected
Chronic spontaneous urticaria
- Extensive routine testing is generally not recommended; guidelines emphasize a focused history and exam
- Consider limited testing to screen for underlying conditions when clinically indicated:
- CBC with differential (eosinophilia may suggest parasitic or allergic cause)
- ESR/CRP (elevated levels may suggest an alternative diagnosis like urticarial vasculitis)
- TSH and thyroid autoantibodies if autoimmune thyroid disease is suspected
- Autologous serum skin test can suggest an autoimmune mechanism but is not routinely required
- Skin biopsy is reserved for atypical cases (lesions lasting more than 24 hours, painful lesions, poor response to antihistamines) to exclude urticarial vasculitis
Chronic inducible urticaria
- Provocation testing based on suspected trigger: ice cube test (cold urticaria), stroking test (dermatographism), exercise challenge (cholinergic urticaria)
Severity assessment
- Urticaria Activity Score (UAS7): a validated 7-day diary tool scoring wheal number and itch severity, used to monitor chronic urticaria and guide treatment escalation
Differential diagnosis
| Condition | Distinguishing feature |
|---|---|
| Urticarial vasculitis | Individual lesions last >24h, resolve with bruising/hyperpigmentation, often painful rather than itchy |
| Erythema multiforme | Target lesions, fixed (non-migratory), often mucosal involvement |
| Mastocytosis (urticaria pigmentosa) | Fixed hyperpigmented macules/papules, positive Darier sign |
| Contact dermatitis | Localized to exposure site, eczematous changes, not migratory |
| Bullous pemphigoid (urticarial phase) | Elderly patients, progresses to tense bullae |
| Serum sickness | Fever, arthralgia, lymphadenopathy accompanying urticaria, 1-2 weeks after antigen exposure |
| Anaphylaxis | Urticaria plus airway, cardiovascular, or GI involvement; medical emergency |
| Polymorphic eruption of pregnancy | Occurs in third trimester, periumbilical sparing, resolves after delivery |
Management
General principles
- Avoid identified triggers (specific foods, drugs, physical stimuli)
- Avoid aggravating factors: NSAIDs, alcohol, overheating, tight clothing, and stress can worsen symptoms
Stepwise pharmacotherapy (international consensus, e.g., EAACI/GA2LEN/EDF/WAO and AAAI guidelines)
- Step 1: Standard-dose second-generation (non-sedating) H1 antihistamines (cetirizine, loratadine, fexofenadine, levocetirizine, bilastine). Preferred over first-generation agents due to lower sedation and anticholinergic burden
- Step 2: If inadequate response after 2-4 weeks, up-titrate the second-generation antihistamine up to fourfold the standard dose (off-label but guideline-endorsed)
- Step 3: If still uncontrolled, add one of:
- Omalizumab (anti-IgE monoclonal antibody) — now a well-established add-on for refractory chronic spontaneous urticaria
- Cyclosporine — alternative for refractory cases, requires monitoring for nephrotoxicity and hypertension
- First-generation antihistamines (diphenhydramine, hydroxyzine) may be used short-term, especially at night, but are limited by sedation
- Leukotriene receptor antagonists (montelukast) are sometimes used as adjuncts, though evidence is weaker
- Short courses of oral corticosteroids can be used for severe acute flares but are not recommended for long-term maintenance due to side effect burden
- Avoid or limit NSAIDs and codeine-related drugs, which can exacerbate mast cell degranulation
Angioedema with airway involvement
- Treat as a medical emergency; if anaphylaxis is suspected (hypotension, wheezing, airway compromise), administer epinephrine promptly and manage per anaphylaxis protocols
Chronic inducible urticaria
- Trigger avoidance plus antihistamine therapy; some subtypes respond to induction of tolerance (e.g., controlled cold exposure for cold urticaria)
Complications and prognosis
- Acute urticaria is typically self-limited, resolving within days to a few weeks
- Chronic spontaneous urticaria follows a variable course: roughly half of patients remit within 1 year, but a significant subset has symptoms persisting for several years
- Angioedema involving the airway, though uncommon in isolated urticaria, poses a risk of life-threatening airway obstruction and requires emergency management
- Chronic urticaria can significantly impair quality of life, sleep, and psychological well-being, with associations to anxiety and depression
- Rarely, persistent atypical lesions (lasting more than 24 hours, painful, residual bruising) should prompt biopsy to exclude urticarial vasculitis, which carries a different prognosis and may require systemic immunosuppressive therapy
- With appropriate antihistamine therapy, most patients, including many with chronic disease, achieve good symptom control
WHEALS — Wheals blanch, Hours (<24h) duration, Edema (dermal), Allergen/Autoimmune triggers, Lip/tongue swelling = angioedema, Scratch (dermatographism) can provoke
Practice questions
1. A 22-year-old woman presents with a 3-day history of intensely itchy, raised, red wheals on her trunk and arms. Each individual lesion fades within a few hours and new ones appear elsewhere. She recently had a sore throat treated with amoxicillin. Vital signs are normal and there is no mucosal or airway involvement. Which of the following is the most appropriate initial management?
2. A 38-year-old man has had daily itchy wheals for the past 10 weeks despite standard-dose cetirizine. He denies any new foods, medications, or infections, and has no systemic symptoms. Physical exam shows typical blanching wheals, each resolving within hours. Laboratory workup, including TSH, is unremarkable. Which of the following is the most appropriate next step in management?
3. A 45-year-old woman with chronic urticaria for 8 months reports that individual skin lesions last 3-4 days, are more painful than itchy, and leave behind a brownish discoloration after they fade. She also reports occasional joint pain. Which of the following is the most appropriate next step?
Frequently asked questions
What causes hives?
Hives are caused by mast cells and basophils releasing histamine into the skin, which dilates blood vessels and increases permeability. Common triggers include viral infections, foods, medications, insect stings, and physical stimuli like cold or pressure. In chronic cases, an autoimmune mechanism involving antibodies against the IgE receptor is often responsible. Many cases, especially chronic ones, remain idiopathic despite thorough evaluation.
What are the first symptoms of hives?
The first symptoms are usually sudden, itchy, raised, red or skin-colored welts that appear on the skin and can vary widely in size and shape. The itching is often intense and lesions may blanch when pressed. Individual spots typically fade within 24 hours, though new ones can keep appearing elsewhere. Some people also develop deeper swelling (angioedema) of the lips, eyelids, or hands.
How is urticaria diagnosed?
Urticaria is diagnosed clinically based on the characteristic appearance and transient nature of the wheals, without routine lab testing in most acute cases. For chronic urticaria (lasting six weeks or more), doctors focus on history and exam, with limited testing such as CBC, ESR/CRP, or thyroid studies only if clinically indicated. Skin biopsy is reserved for atypical presentations to rule out urticarial vasculitis.
Is urticaria curable?
Acute urticaria usually resolves completely within days to a few weeks, often without needing long-term treatment once the trigger is removed. Chronic spontaneous urticaria is not always curable but is highly manageable; about half of patients go into remission within a year, while others need ongoing antihistamine therapy or advanced treatments like omalizumab. There is no guaranteed cure for chronic cases, but good symptom control is achievable for most patients.
Urticaria vs urticarial vasculitis — what is the difference?
The key difference is lesion duration and resolution: ordinary urticaria wheals resolve within 24 hours and leave no mark, while urticarial vasculitis lesions persist longer than 24 hours and resolve with bruising or hyperpigmentation. Urticarial vasculitis lesions are also more often painful or burning rather than itchy, and may be accompanied by systemic symptoms like joint pain or fever. Diagnosis of urticarial vasculitis requires skin biopsy showing vessel inflammation.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: L50
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.