Urticaria

e.All of the above a.The lesions fully resolve (characteristic of urticaria) b.She recently began new medications (likely etiology) c.The lesions last 8hrs (individual wheals rarely last over 12 hrs.) d.Three-day history of rash (this is acute urticaria)

46-year-old woman with a 3-day history of a widespread pruritic rash. Individual lesions last approximately 8hrs and then fully resolve. Vital signs: afebrile, HR 74, BP 120/70, RR 16, O2 sat 98% on RA Skin: diffuse erythematous papules coalescing into plaques (wheals) No associated bruising What important feature(s) are revealed in the history?

Assess ABC's (airway, breathing, circulation) Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death Patients with anaphylaxis may have no skin lesions, lesions of angioedema, and/or typical urticarial wheals Morphology of the skin lesion does not matter •Patients with angioedema are not more likely to have anaphylaxis compared to patients with urticaria ABC's first! Recruit more help. May need to triage to higher level of care (in clinic this means calling 911). 51

Anaphylaxis Vitals: T 98.6F, HR 110, BP 90/50, RR 34 General: anxious-appearing woman sitting upright with difficulty breathing, unable to speak in full sentences Respiratory: tachypneic, using accessory muscles, bilateral rhonchi Skin: periorbital edema, scattered erythematous wheals on the trunk

First-line therapy for anaphylaxis includes epinephrine, IV fluids and oxygen Administer 0.3-0.5ml in 1:1000 epinephrine dilution IM repeating every 10-20min as necessary; for children <30kg, the dose is 0.01mL/kg/dose. Make sure airway is patent or else intubation may be emergently necessary Patients who have severe reactions requiring epinephrine should be monitored in the hospital

Anaphylaxis: Treatment

Angioedema can be caused by the same pathogenic mechanisms as urticaria, but the pathology is in the deep dermis and subcutaneous tissue and swelling is the major manifestation Angioedema commonly affects the face or a portion of an extremity •Involvement of the lips, cheeks, and periorbital areas is common, but angioedema also may affect the tongue, pharynx, larynx and bowels May be painful or burning, but usually not pruritic May last several days

Angioedema

The following are examples of H1 antihistamines: •1st Generation -Diphenhydramine (OTC) -Hydroxyzine (Rx, generic) -Chlorpheniramine (OTC) •2nd Generation -Cetirizine (OTC) -Loratadine (OTC) -Fexofenadine (OTC)

Antihistamines

Ask about symptoms of anaphylaxis, including: chest tightness or difficulty breathing, hoarse voice or throat tightness, nausea, vomiting, abdominal pain, lightheadedness In addition to the skin exam, the physician should obtain a set of vital signs and evaluate for respiratory distress (dyspnea, wheeze, bronchospasm, stridor) and hypotension For acute urticaria, no lab testing is required •Laboratory testing is generally driven by associated signs and symptoms (e.g. C1 esterase deficiency only causes angioedema, not hives)

Clinical Evaluation

Idiopathic Infection •Upper respiratory, streptococcal infections, helminths •Most common cause of urticaria in children is viral illness Food reactions •Shellfish, nuts, fruit, etc. Drug reactions IV administration •Blood products, contrast agents

Common Causes of Acute Urticaria

Most common form of physical urticaria Sharply localized edema or wheal within seconds to minutes after the skin has been rubbed Affects 2-5% of the population

Dermatographism

Medications are a common cause of urticaria and angioedema •Penicillin and related antibiotics are common via the IgE-mediated mechanism •Aspirin is a common cause via a non-IgE-mediated mechanism •30% of chronic urticaria is exacerbated by aspirin/NSAID use Many patients ask about detergent use. However, it generally causes irritant or allergic contact dermatitis, not urticaria.

Diagnosis: Medication-induced Urticaria

Idiopathic: over 50% of chronic urticaria Physical urticarias: many patients with chronic urticaria have physical factors that contribute to their urticaria •These factors include pressure, cold, heat, water (aquagenic), sunlight (solar), vibration, and exercise •Cholinergic urticaria is triggered by heat and emotion •The diagnosis of pure physical urticaria is made when the sole cause of a patient's urticaria is a physical factor Autoimmune Urticaria: possibly a third or more of patients with chronic urticaria Other: infections, ingestions, medications

Etiology of Chronic Urticaria

Symptoms of chronic urticaria can be severe and impair the patient's quality of life (QOL) In most patients, chronic urticaria is an episodic and self-limited disorder Average duration of disease is two to five years In patients with idiopathic chronic urticaria, there is a rate of spontaneous remission at one year of approximately 30 to 50 percent However, symptoms extend beyond five years in nearly one-fifth of patients

Natural History and Prognosis

Referral to a dermatologist and biopsy should be performed in patients with one or more of the following features: •Individual lesions that persist beyond 48 hours, are painful or burning rather than pruritic, or have accompanying petechial characteristics •Systemic symptoms •Lack of response to antihistamines •Lesions that leave pigmentation changes upon resolution

Referral to Dermatology

Urticaria (hives) is a vascular reaction of the skin characterized by wheals surrounded by a red halo or flare. Urticaria is classified as acute or chronic. Acute urticaria is defined as periodic outbreaks of urticarial lesions that resolve within six weeks. Over 50% of chronic urticaria is idiopathic. The most common cause of urticaria in kids is a viral illness. Oral H1 antihistamines are first-line treatment for acute and chronic urticaria. The presence of systemic symptoms should signal the possibility that an urticarial rash is not ordinary urticaria. Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. Remember to ask about symptoms of anaphylaxis, including: chest tightness or difficulty breathing, hoarse voice or throat tightness, nausea, vomiting, abdominal pain, lightheadedness. The 1st step in management of a patient with signs and symptoms of anaphylaxis is to assess airway, breathing, circulation, and adequacy of mentation. Call for help if you suspect a patient has anaphylaxis.

Take Home Points

Oral H1 antihistamines are the first-line treatment for acute and chronic urticaria 1st-generation H1 antihistamines are less well-tolerated due to sedation, so are often taken at bedtime •e.g. 10-50 mg hydroxyzine 1-2 hours before bedtime •Can start with smaller doses (10 mg) to allow the patient to manage the sedative effects •Remember to warn patient not to drive a car or operate other dangerous machines within 4-6 hours of taking this medication •Do not take with other sedating medications 2nd-generation H1 antihistamines (e.g. Loratadine) are better tolerated with fewer sedative and anticholinergic effects and may be used in patients intolerant of or inadequately controlled by 1st-generation agents Certain populations, including children, the elderly, and patients with renal or hepatic impairment may require dosage calculation or adjustments when using H1 antihistamines Also used with caution in patients with glaucoma, prostatic hyperplasia, and respiratory disease H2 antihistamines have mixed data on their efficacy for urticaria and are generally not used as first-line therapy

Treatment: Antihistamines

Urticaria and angioedema may occur in any location together or individually. Angioedema and/or urticaria may be the cutaneous presentation of anaphylaxis, so assessment of the respiratory and cardiovascular systems is vital.

Urticaria & Angioedema

•A subset of pediatric urticaria with larger polycyclic or annular lesions with dusky and ecchymotic centers along with acral edema. •We can distinguish from erythema multiforme (EM) because in EM, individual lesions are fixed for at least 7 days. Also, urticaria multiforme improves with antihistamines.

Urticaria Multiforme

Urticaria (hives) is a vascular reaction of the skin characterized by wheals surrounded by a red halo or flare (area of erythema) Cardinal symptom is PRURITUS (itch) Urticaria is caused by swelling of the upper dermis Up to 20% of the population experience urticaria at some point in their lives

Urticaria The Basics

Lesions typically appear over the course of minutes, enlarge, and then disappear within hours Individual wheals rarely last >12hrs Surrounding erythema will blanch with pressure Urticaria may be acute or chronic •Acute = new onset urticaria < 6 weeks •Chronic = recurrent urticaria (most days) > 6 weeks Most urticaria is acute and resolves

Urticaria: Clinical Findings

The mast cell is the major effector cell in urticaria Immunologic Urticaria: antigen binds to IgE on the mast cell surface causing degranulation, which results in release of histamine •Histamine binds to H1 and H2 receptors to cause arteriolar dilatation, venous constriction and increased capillary permeability, causing swelling and itch. Non-Immunologic Urticaria: not dependent on the binding of IgE receptors •For example, aspirin may induce histamine release through a pharmacologic mechanism where its effect on arachidonic acid metabolism causes a release of histamine from mast cells. •Physical stimuli may induce histamine release through direct mast cell degranulation.

Urticaria: Pathophysiology

Ibuprofen

What medication can contribute to urticaria