From the Guidelines
Diagnosing urticaria requires a thorough medical history, physical examination, and sometimes specific tests, with a focus on identifying the underlying cause and distinguishing it from other conditions such as anaphylaxis or angio-oedema. The diagnosis of urticaria involves examining the skin lesions, looking for characteristic raised, red, itchy welts that blanch with pressure and typically resolve within 24 hours 1. A detailed history includes the timing, duration (acute if less than 6 weeks, chronic if longer), and pattern of outbreaks, as well as potential triggers like foods, medications, insect stings, physical stimuli (cold, heat, pressure), or recent infections.
Key Diagnostic Steps
- Examine the skin lesions for characteristic features
- Take a detailed medical history to identify potential triggers and patterns
- Order blood tests to check for elevated inflammatory markers, complete blood count, or specific antibodies if necessary
- Consider skin biopsy to rule out other conditions like urticarial vasculitis
- Use allergy testing through skin prick tests or specific IgE blood tests to identify triggers
- Perform provocation tests for physical urticarias, such as applying cold, heat, or pressure to see if hives develop
- Keep a food diary to help identify dietary triggers, especially in cases of chronic urticaria
According to the most recent guidelines, the diagnosis of urticaria is primarily clinical, based on the characteristic appearance of the lesions and their transient nature 1. It's essential to distinguish urticaria from other conditions like anaphylaxis, which requires prompt epinephrine administration, and angio-oedema, which may be caused by angiotensin-converting enzyme (ACE) inhibitors or C1 esterase inhibitor deficiency 2.
Differential Diagnosis
- Anaphylaxis: requires prompt epinephrine administration
- Angio-oedema: may be caused by ACE inhibitors or C1 esterase inhibitor deficiency
- Urticarial vasculitis: presents with urticaria clinically but small vessel vasculitis histologically
- Autoinflammatory syndromes: typically develop spontaneous weals, pyrexia, and malaise, with other features that define the disease phenotype.
In real-life clinical practice, it's crucial to prioritize the patient's safety and well-being, and to err on the side of caution when diagnosing and managing urticaria. This may involve consulting with specialists, such as allergists or dermatologists, to ensure accurate diagnosis and effective treatment. By following a thorough diagnostic approach and considering the latest evidence, healthcare providers can provide optimal care for patients with urticaria.
From the Research
Diagnosis of Urticaria
To diagnose urticaria, the following steps can be taken:
- A thorough medical history and physical examination are necessary to uncover diagnostic clues 3, 4
- Diagnosis is made clinically, with anaphylaxis being ruled out 5, 6
- A simple laboratory workup may be considered unless elements of the history or physical examination suggest specific underlying conditions 5, 6
- A comprehensive medical history for patients with chronic urticaria should include items such as time of disease onset, duration, shape, size, color, and distribution of wheals, associated angioedema, atopy, and triggering factors 4
Key Considerations
- Urticaria is caused by immunoglobulin E- and non-immunoglobulin E-mediated release of histamine and other inflammatory mediators from mast cells and basophils 5, 6
- Chronic urticaria is idiopathic in 80% to 90% of cases, and only a limited nonspecific laboratory workup should be considered unless elements of the history or physical examination suggest specific underlying conditions 5
- A checklist for a complete chronic urticaria medical history can be used to support accurate diagnosis of the disease 4