Urticaria
Urticaria, also known as hives, weals or nettle rash, is a superficial swelling of the skin that causes a red, raised and intensely itchy rash.
This updated UKMLA guide to urticaria (acute and chronic) is based on NICE CKS, which covers types, causes, symptoms, diagnosis, and management.
Definition and Types
Urticaria refers to the superficial swelling of the skin (epidermis and mucous membrane)
- Acute urticaria: last <6 weeks
- Chronic urticaria: last ≥6 weeks
Angioedema is a deeper form of urticaria:
- Caused by transient swelling of deeper dermal, subcutaneous and submucosa tissues
- Often affecting the face (lips, tongue, eyelid), genitalia, hands or feet
Urticaria and angioedema can co-exist (~40% of cases), but either can occur separately
Causes and Risk Factors
Urticaria is driven by mast cells releasing histamine and other inflammatory mediators (e.g. leukotrienes, prostaglandins), causing
- Pruritus
- ↑ Vascular permeability
- Oedema
Acute Urticaria (<6 Weeks)
Acute urticaria may occur spontaneously, or in response to a trigger:
- Acute viral infection (viral-induced urticaria is common in children)
- Allergic reaction to
- Certain foods (e.g. milk, eggs, peanuts, tree nuts, shellfish)
- Insect bites and stings
- Contact allergens (e.g. latex)
- Certain drugs (e.g. penicillins, aspirin, NSAIDs, vaccinations)
Chronic Urticaria (≥6 weeks)
There are 2 main types of chronic urticaria:
| Chronic spontaneous urticaria | Urticaria occurs with no identifiable external cause (but symptoms may be aggravated by heat, stress, drugs and infection)
This includes autoimmune urticaria (urticaria occurs in the presence of IgG to IgE receptors +/- associated with other autoimmune conditions) |
| Chronic inducible urticaria | Urticaria occurs in response to a physical stimulus
It can be further classified according to the physical stimulus
|
Chronic urticaria that is painful and persistent (lesions remain for >24 hours) should raise suspicion of vasculitic urticaria. There may be systemic symptoms, such as fever, malaise, and arthralgia.
Clinical Features and Diagnosis
Urticaria is primarily a clinical diagnosis
3 typical features of urticaria:
- Pruritus and/or burning sensation
- Central swelling of variable size (red / white), usually with a surrounding erythema / flare
- Fleeting nature – skin returns to normal within 1-24 hours
Investigations for Underlying Cause
Consider the following investigations to identify underlying causes / treatable associated conditions / trigger factors:
- LFT
- TFT (+ve thyroid antibodies + chronic urticaria suggests autoimmune urticaria)
- ESR / CRP (↑ inflammatory markers suggest underlying systemic condition)
- FBC (↑ eosinophil count may suggest drug-induced reaction or parasitic infection)
- H. pylori testing (if GI symptoms are present) (see the Helicobacter Pylori Infection article for more information)
- Allergy testing
- Elimination of suspected food or drugs
- Skin biopsy (for atypical presentation or suspected urticarial vasculitis)
- Urinalysis (for suspected vasculitis)
- Physical challenge (for chronic inducible urticaria)
Red flags Features (Anaphylaxis)
The most important differential diagnosis to exclude is anaphylaxis, as urticaria may occur as part of the presentation.
Assess urgently for ABC problems:
- Airway – angioedema, stridor, drooling
- Breathing – widespread wheezing, hypoxia, cyanosis
- Circulation – hypotension, tachycardia, syncope/collapse, reduced GCS
Anaphylaxis is a potentially life-threatening medical emergency, see the Anaphylaxis article for more information.
Management
Advise patient:
- If there is an identifiable trigger → avoid it if possible
- Mild urticaria with an identifiable and avoidable cause/trigger is likely to be self-limiting without treatment
Symptomatic (pharmacological) management:
- 1st line: non-sedating antihistamine (e.g. cetirizine, fexofenadine, loratadine) for up to 6 weeks
- For severe symptoms, give a short-course (up to 7 days) of oral corticosteroid (e.g. prednisolone) in addition to the antihistamine
- Consider referral if a steroid is needed in <16 y/o
- Do not repeat the course of oral steroids unless advised by a specialist
Ongoing antihistamine therapy (if symptoms improved):
- If the symptoms are short-lived and frequent recurrence is unlikely → prescribe to be taken as required or prophylactically
- If the symptoms are likely to be persistent or recurrent (e.g. chronic spontaneous urticaria) → prescribe daily antihistamines for 3-6 months, then review
If there is inadequate response to 1st line non-sedating antihistamine, consider the following options:
- Increase the dose to up to 4x the licensed dose (off-label) in adults (seek a specialist before doing so in children)
- Switch to an alternative non-sedating antihistamine
- Add an LTRA (e.g. montelukast, zafirlukast) in addition to the antihistamine
- Topical antipruritic treatment (e.g. calamine lotion, topical menthol aqueous cream)
- Add a sedating antihistamine (e.g. chlorphenamine) at night if the itch is interfering with sleep
- Refer to a dermatologist or immunologist