One-liner#

Evaluate urticaria (hives) to identify anaphylaxis risk and triggers while managing symptoms with antihistamines, distinguishing acute (<6 weeks) from chronic urticaria which requires different workup and management.

Quick nav#

• Red flags / send to ED
• Key history
• Focused exam
• Differential (quick pattern recognition)
• Workup
• Initial management
• Management by diagnosis
• Follow-up
• Patient instructions
• Smartphrase snippets

Red flags / send to ED#

• Angioedema of lips, tongue, or throat
• Difficulty breathing, wheezing, stridor
• Hypotension, tachycardia, dizziness
• Abdominal pain, vomiting (GI anaphylaxis)
• History of anaphylaxis with current urticaria
• Urticaria after known allergen exposure (bee sting, peanut, etc.)

Call 911 / give epinephrine if:

• Airway compromise
• Hypotension
• Two or more organ systems involved (skin + respiratory, skin + GI, etc.)

Key history#

Timing:

• Duration: <6 weeks = acute; >6 weeks = chronic
• Individual wheals: last <24 hours (if >24 hours, consider urticarial vasculitis)
• Time of day: worse at night suggests physical urticaria or mast cell activation

Triggers (acute urticaria):

• Foods: shellfish, peanuts, tree nuts, eggs, milk, wheat (usually within 2 hours)
• Medications: NSAIDs, antibiotics (penicillins, sulfonamides), ACE inhibitors (angioedema)
• Insect stings
• Infections: viral URI often precedes acute urticaria
• Contact: latex, animals

Physical triggers (chronic urticaria):

• Pressure (delayed pressure urticaria)
• Cold (cold urticaria)
• Heat/exercise (cholinergic urticaria)
• Sun (solar urticaria)
• Water (aquagenic urticaria—rare)
• Vibration
• Dermographism (scratching causes wheals)

Associated symptoms:

• Angioedema: lip, eyelid, hand, foot, genital swelling
• Respiratory: wheezing, throat tightness, difficulty breathing
• GI: abdominal pain, nausea, vomiting
• Systemic: fever, arthralgias (suggests urticarial vasculitis or serum sickness)

Medication review:

• NSAIDs (can trigger or worsen urticaria)
• ACE inhibitors (angioedema, can occur years after starting)
• Aspirin
• Opioids (direct mast cell degranulation)
• Contrast dye exposure

Past history:

• Prior episodes
• Known allergies
• Atopic history
• Autoimmune disease (associated with chronic urticaria)
• Thyroid disease (associated with chronic urticaria)

Focused exam#

• Vitals: hypotension, tachycardia (anaphylaxis); fever (infection, vasculitis)
• Airway: stridor, voice changes, tongue/lip swelling
• Skin:
  • Wheals: raised, erythematous, blanching, edematous plaques
  • Distribution: localized vs generalized
  • Dermographism: stroke skin with tongue depressor—wheal appears in minutes
  • Duration of individual lesions (ask patient to circle one and time it)
• Angioedema: lips, eyelids, hands, feet, genitals (deeper swelling, not itchy)
• Lungs: wheezing
• Abdomen: tenderness (GI involvement in anaphylaxis)

Key exam finding: Individual wheals should resolve within 24 hours. If lesions persist >24 hours or leave bruising/pigmentation, consider urticarial vasculitis.

Differential (quick pattern recognition)#

Common/likely (outpatient)#

Can’t-miss / urgent#

Workup#

Acute urticaria (<6 weeks): Usually NO workup needed

• Most cases are idiopathic or post-viral
• Testing rarely identifies trigger
• Treat empirically with antihistamines

When to test in acute urticaria:

• Suspected anaphylaxis: tryptase level (within 4 hours of reaction)
• Suspected allergic trigger: consider allergy referral for skin testing (not during acute episode)

Chronic urticaria (>6 weeks): Limited workup

When NOT to test:

• Routine acute urticaria responding to antihistamines
• Chronic urticaria without systemic symptoms (extensive panels rarely helpful)
• “Allergy panels” for chronic urticaria (low yield, high cost)

Initial management#

Acute urticaria:

• Second-generation antihistamine (cetirizine, loratadine, fexofenadine)
• Can double standard dose if needed
• Add first-generation antihistamine (diphenhydramine) for breakthrough or nighttime
• Short course of steroids for severe cases
• Prescribe epinephrine auto-injector if any angioedema or anaphylaxis history

Chronic urticaria:

• Step-up approach (see management section)
• Avoid NSAIDs (can worsen)
• Identify and avoid physical triggers

Management by diagnosis#

Acute urticaria#

Education:

• Very common; affects 20% of people at some point
• Usually self-limited; resolves in days to weeks
• Often no trigger identified (post-viral common)
• Antihistamines are safe and effective

Treatment:

Follow-up: 1-2 weeks if not resolving; if >6 weeks, becomes chronic urticaria.

Chronic spontaneous urticaria#

Education:

• Defined as urticaria >6 weeks
• Often no trigger identified despite extensive testing
• Autoimmune mechanism in ~50% (autoantibodies to IgE receptor)
• Can last months to years; ~50% resolve within 1 year
• Goal is symptom control, not cure

Treatment (step-up approach per guidelines):

Step 1: Standard-dose second-generation antihistamine

Step 2: Up-dose antihistamine (2-4x standard dose)

Step 3: Add-on therapy (if step 2 inadequate after 2-4 weeks)

Step 4: Specialist referral for refractory cases

• Omalizumab (Xolair): anti-IgE monoclonal antibody; allergy/derm-initiated
• Cyclosporine: immunosuppressant; specialist-initiated

Avoid:

• Long-term systemic steroids (side effects outweigh benefits)
• First-generation antihistamines as monotherapy (sedation, anticholinergic effects)

Follow-up: 4-6 weeks to assess response; step up if inadequate control.

Angioedema (with urticaria)#

Education:

• Deeper swelling than urticaria; involves lips, eyelids, hands, feet, genitals
• When occurs with urticaria, usually same mechanism (mast cell-mediated)
• Can be life-threatening if involves tongue/throat
• Prescribe epinephrine auto-injector

Treatment:

• Same as urticaria (antihistamines, steroids for severe)
• Always prescribe epinephrine auto-injector
• Avoid ACE inhibitors (can worsen any angioedema)

Follow-up: Allergy referral for evaluation and anaphylaxis action plan.

ACE inhibitor-induced angioedema#

Education:

• Caused by bradykinin accumulation (NOT histamine-mediated)
• Can occur years after starting ACE inhibitor
• Angioedema WITHOUT urticaria is key feature
• Antihistamines and steroids have limited efficacy
• Must stop ACE inhibitor permanently

Treatment:

• Stop ACE inhibitor immediately and permanently
• Do NOT switch to another ACE inhibitor
• ARBs: small cross-reactivity risk (~3%); can consider with caution
• Antihistamines and steroids may help but less effective than in mast cell-mediated angioedema
• If airway involvement: ED immediately

Follow-up: 1-2 weeks to ensure resolution; discuss alternative antihypertensives.

Physical urticarias#

Dermographism:

• Most common physical urticaria
• Wheals appear where skin is stroked/scratched
• Treatment: antihistamines PRN; avoid scratching

Cold urticaria:

• Wheals on cold-exposed skin
• Risk of anaphylaxis with cold water immersion (swimming)
• Treatment: antihistamines before cold exposure; avoid cold; prescribe epinephrine

Cholinergic urticaria:

• Small punctate wheals with exercise, heat, stress
• Treatment: antihistamines before triggers; cool down slowly after exercise

Delayed pressure urticaria:

• Swelling hours after sustained pressure (tight clothing, sitting)
• Treatment: antihistamines; avoid prolonged pressure; may need steroids for severe

Follow-up: 4-6 weeks; allergy referral if refractory.

Urticarial vasculitis#

Education:

• Inflammation of small blood vessels presenting as urticaria-like lesions
• Key features: lesions last >24 hours, painful more than itchy, leave bruising
• Can be associated with systemic disease (lupus, hepatitis, malignancy)
• Requires biopsy for diagnosis

Treatment:

• Antihistamines (often less effective than in true urticaria)
• NSAIDs or colchicine for mild cases
• Systemic steroids or immunosuppressants for severe (specialist-managed)

Workup: Skin biopsy, CBC, CMP, ESR, CRP, complement levels, ANA, hepatitis serologies

Follow-up: Derm/rheum referral for management.

Follow-up#

• Acute urticaria: 1-2 weeks if not resolving
• Chronic urticaria: 4-6 weeks to assess treatment response
• Angioedema: Allergy referral; 1-2 weeks to ensure resolution
• ACE inhibitor angioedema: 1-2 weeks; discuss alternative BP meds

Return precautions:

• Difficulty breathing or swallowing
• Swelling of lips, tongue, or throat
• Dizziness or feeling faint
• Hives spreading rapidly with other symptoms
• Not improving with antihistamines after 1-2 weeks

Patient instructions#

• Hives (urticaria) are very common and usually not dangerous.
• Take antihistamines as directed. You may need to take them regularly, not just when you have hives.
• Avoid known triggers if identified (certain foods, medications, cold, heat).
• Avoid aspirin and ibuprofen (NSAIDs) as they can make hives worse. Use acetaminophen (Tylenol) for pain.
• Individual hives should go away within 24 hours, though new ones may appear.
• If you have been prescribed an epinephrine auto-injector (EpiPen), carry it with you at all times.
• Go to the ER immediately if you have trouble breathing, throat tightness, tongue swelling, or feel faint.

Smartphrase snippets#

.URTICARIAACUTE Acute urticaria, [duration]. No angioedema or systemic symptoms. No clear trigger identified / Likely triggered by [trigger]. Plan: cetirizine 10 mg daily (may increase to BID if needed), avoid NSAIDs. Discussed return precautions including throat swelling, difficulty breathing, or worsening symptoms. Follow-up in 1-2 weeks if not resolving.

.URTICARIACHRONIC Chronic spontaneous urticaria (>6 weeks duration). No identifiable trigger. No features of urticarial vasculitis (lesions <24 hours, no bruising). Labs: [CBC, TSH ordered / previously normal]. Current treatment: [regimen]. Plan: [step up to higher dose antihistamine / add montelukast / continue current regimen]. Discussed chronic nature and goal of symptom control. Follow-up in 4-6 weeks.

.ANGIOEDEMA Angioedema of [location] with/without urticaria. No airway involvement. [ACE inhibitor use: yes/no]. Plan: [stop ACE inhibitor permanently / antihistamines and short course steroids]. Prescribed epinephrine auto-injector with instructions. Discussed anaphylaxis warning signs and when to use EpiPen. Allergy referral placed. Return to ED immediately if throat swelling, difficulty breathing, or feeling faint.