Urticaria is characterised by fluctuating weals and/or angio-oedema. A weal consists of three typical features:

• a central swelling of variable size (from a few millimetres to hand-sized lesions), almost invariably surrounded by a reflex erythema
• associated itching or, sometimes, burning sensation
• a fleeting nature, with the skin returning to its normal appearance, usually within 1–24 hours

Angio-oedema is characterised by:

• A sudden, pronounced swelling of the lower dermis and subcutis, which is pale rather than pink and may be painful rather than itching:
• Frequent involvement below mucous membranes
• Resolution that is slower than for weals and can take up to 72 hours

The clinical history of the symptoms and suspected precipitants/exacerbating factors is paramount, along with examination of the symptoms if possible.

The history should include.

• Date of onset
• Nature and severity of symptoms
• Exacerbating factors (e.g., heat, cold, pressure, stress, medications)
• Treatment required and efficacy.
• Thorough assessment to exclude underlying pathology (e.g., chronic infection)
• Suspected triggers (likely only if the symptoms are predictably associated with exposure, and remit upon avoidance. If the symptoms persist despite avoidance the suspect can be excluded as a cause).
• If associated with airway/breathing/circulation/neurological features, see anaphylaxis pathway
• If history suggests food or drug allergy (in the absence of anaphylaxis) please click for appropriate pathway

ACE inhibitor treatment can cause angioedema (without urticaria) even after months or years of treatment and must be stopped in patients presenting with angioedema.

Angioedema in the absence of urticaria also raises the possibility of hereditary/acquired angioedema: check complement C4 to exclude this (see ‘Red Flags’ and ‘Investigations’.

Please note:

• Recurrent sensation of isolated throat swelling without other features of allergy – consider alternative diagnosis (e.g., globus, vocal cord dysfunction) and consider ENT referral.
• Periorbital oedema with eczema/dry skin rash – consider periorbital eczema and referral to Dermatology for patch testing.

Airway compromise with angioedema +/- urticaria

• treat as anaphylaxis following the resuscitation council guidelines
• see anaphylaxis guideline

Hereditary/acquired angioedema

• patients with isolated angioedema with no history of urticaria raises the possibility of hereditary/acquired angioedema
• It is recommended a C4 blood test is checked prior to referral.
• A low result indicates possibility of rarer causes of life-threatening airway swelling which will not respond to antihistamines or adrenaline. The allergy service will see these patients urgently.

No investigations required prior to referral.

The exception to this is for patients with:

• patients with isolated angioedema with no history of urticaria raises the possibility of hereditary/acquired angioedema
• It is recommended a C4 blood test is checked prior to referral.
• A low result indicates possibility of rarer causes of life-threatening airway swelling which will not respond to antihistamines or adrenaline. The allergy service will see these patients urgently.

1. Spontaneous urticaria and angioedema should be treated initially with oral non-sedating antihistamines.

a) Higher than licensed doses may be required - up to 4x/day. This is supported by British and European guidelines and there is good safety data.

b) These increased doses must not be used in pregnancy, and attention should be paid to interactions with other drugs.

c) Patients with ongoing symptoms (rash or swelling) despite high dose four times daily prophylaxis with non-sedating antihistamines, consider adding Montelukast 10mg daily (unlicensed) +/- H2 antagonist in addition to antihistamines.

2. All patients with angioedema should avoid ACE inhibitors, as well as related drugs such as neprolysin inhibitors (e.g., sacubitril in Entresto).

3. Patients with urticaria and/or angioedema should be advised to use NSAIDS with caution as these can exacerbate Chronic Spontaneous Urticaria (CSU). DPP4 inhibitors (“gliptins”) can also be associated with angioedema.

The information essential for clinical triage is outlined on the referral form.

For efficiency and to minimise returned referrals, use of the referral form is recommended.

Referrals not on the referral form will be accepted as long as all the essential information is included in a referral letter.

Referral Criteria

Urgent 

• Adults (16 years and over) with angioedema without urticaria and a low C4 (see Red Flags)

Routine

Adults (16 years and over):

• With urticaria and/or angioedema persisting for 3 months or more despite 4 x daily non-sedating antihistamine and Montelukast 10mg nocte
• With a history of cold inducible urticaria
• angioedema on ACE-I medication
  • stop ACE-I – refer if symptoms persist 3-4 months after the ACE-I has been stopped and despite four times daily non-sedating antihistamines and Montelukast

• If there is diagnostic uncertainty

Please note:

• Recurrent sensation of isolated throat swelling without other features of allergy – consider alternative diagnosis (e.g., globus, vocal cord dysfunction) and consider ENT referral.
• Periorbital oedema with eczema/dry skin rash – consider periorbital eczema and referral to Dermatology for patch testing.

Referral instructions

Refer to Clinical Immunology Service

• Refer using e-Referral Service
  • Specialty: Allergy
  • Clinic type: Allergy
  • Service: DRSS-Eastern-Allergy-Devon ICB- 15N

Referral form

Adult allergy clinic referral form - no merge fields

GP Information

Devon Formulary guidance: Management of urticaria

Devon Formulary guidance: antihistamines

onlinelibrary.wiley - guideline for the management of chronic urticaria and angioedema

Patient Information

Chronic urticaria (Hives)

Pathway Group

This guideline has been signed off on behalf of NHS Devon.

Publication date: March 2016

Updated: December 2024