Information
Editors
Hives (Urticaria)
Essentials
- Acute urticaria is often associated with an infection.
- The majority of chronic cases are due to autoimmune urticaria or idiopathic urticaria.
- Unnecessary laboratory tests should be avoided as well as associating urticaria with allergies or food intolerance.
- Effective symptomatic treatment.
Epidemiology
- Urticaria is a common condition. The lifetime incidence of urticaria in the general population is about 20%.
Diagnosis
- A typical feature of urticaria is rapidly developing, raised and pruritic wheals (pictures ) with or without surrounding erythema.
- Wheals may cover large skin areas, and their size varies from 1 mm to larger confluent wheals.
- Pruritus is usually most severe when the wheals are developing, but signs of scratching are rare.
- The wheals rise and disappear whilst migrating from place to place. Any single wheal will characteristically not persist on the same spot for longer than 24 hours.
- No vesicle formation, scaling or ulceration is noted.
- About half of patients will also have angioedema (picture ), either as an independent symptom or associated with urticaria.
- The diagnosis is not likely to be urticaria if a single lesion persists in the same location for more than 24 hours or leaves a mark upon healing, e.g. pigmentation, slight bruising or purpura.
Acute urticaria (duration < 6 weeks)
- Usually associated with infections (e.g. viral upper respiratory tract infection)
- The causal relationship between urticaria and infection is rarely confirmed.
- Drugs used during the infection are often considered culprits even though only rarely is a drug reaction the cause of urticaria.
- Moreover, acute urticaria may be the first sign of anaphylaxis.
- Subsequent deterioration of general condition, hypotension and bronchial obstruction
- If the patient remains otherwise well, no laboratory investigations are usually indicated.
- Additional investigations should aim to identify the infection that may have triggered urticaria and are based on presenting symptoms (basic blood count with platelets, CRP, streptococcal throat culture, ultrasonography of the sinuses, chest x-ray etc.). Investigations are carried out only if the results influence treatment.
Contact urticaria
- Wheals may develop in sensitised patients on skin areas that have been in direct contact with a particular allergen (immediate allergy; animal saliva, natural rubber etc.).
- The causal relationship is often obvious, and sensitisation may be demonstrated with investigations that test immediate allergy (skin prick tests and serum specific IgE antibodies Diagnostic Tests in Dermatology).
Recurrent acute urticaria
- A comprehensive and detailed history is important in cases of recurrent acute urticaria.
- Is urticaria provoked by medicines, for example NSAIDs, certain foods, physical irritants or exertion?
- The combined effect of several factors is often needed to trigger urticaria, e.g. feverish cold and alcohol or certain foods (e.g. wheat) and exertion.
Chronic urticaria (duration > 6 weeks)
Autoimmune urticaria
- Autoimmune urticaria is the most common type of chronic urticaria.
- Mild symptoms are usually present daily with occasional periods of exacerbation.
- Exacerbations may be triggered by infections or NSAIDs.
- Autoimmune urticaria may react poorly to antihistamines.
- In some cases, antibody assays may be positive (histamine release test).
- Patients may have other concurrent autoimmune diseases (e.g. autoimmune thyroiditis Chronic Autoimmune Thyroiditis); the exclusion tests for these conditions include serum TSH and anti-thyroid peroxidase antibodies.
Physical urticarias
- The cornerstone of diagnosis is the patient's history http://www.dynamed.com/condition/chronic-urticaria#MAKING_THE_DIAGNOSIS. Challenge testing is rarely needed.
- The most important management measure is the avoidance of triggering factors.
- Dermographism (picture )
- Triggered occasionally by an infection. Urticaria persists even after the infection has resolved and will usually last for a few years.
- Test: scratch the skin on the back with a blunt instrument (e.g. a spatula) and wait for 5 minutes. The test is positive if raised wheals develop at the scratched skin areas.
- Pressure urticaria
- Mechanical pressure will induce a swelling that occurs either immediately or with a delay of about 24 hours (more common) at the pressure site.
- Cholinergic urticaria
- Particularly in young adults; highly pruritic wheals of 1-2 mm in diameter occur on the chest and torso after physical or emotional stress. The symptoms do not last long.
- Cold urticaria
- As cold skin warms up, redness and swelling develop on certain areas of the skin.
- The phenomenon usually lasts for some years. Symptoms may also be triggered by touching a cold object.
- Solar urticaria
- A rare form of photosensitivity dermatitis, often refractory to treatment and characterised by local swelling only minutes after exposure to natural or artificial light.
Angioedema
- See article Angioedema.
- Often occurs concurrently with urticaria.
- In about 10% of patients with chronic urticaria, the only manifestation is recurrent angioedema without urticarial wheals.
- Swelling often involves the lips or eyelids and lasts for 1-3 days.
- The patient reports a burning sensation and pain, rather than itching.
- Treatment response to antihistamines is generally poor.
- A common cause is medication with ACE inhibitors or angiotensin receptor blockers. Even when these drugs are used on a regular basis, symptoms occur only occasionally. Symptoms are caused by aetiology other than an allergic mechanism.
- Moreover, drug hypersensitivity (e.g. NSAIDs) may cause angioedema. In this case, symptoms emerge whenever the drug is taken.
- If a patient presents with episodes of angioedema alone, the differential diagnosis should include anaphylaxis Anaphylaxis and hereditary angioedema (HAE) Hereditary Angioedema (HAE) and ACE Inhibitor-Induced Angioedema.
Specialist consultation
- Recurrent urticaria may warrant additional investigations carried out under the supervision of a dermatologist.
- In chronic urticaria that is severe or refractory to appropriately carried out conventional treatment, a dermatologist should be consulted http://www.dynamed.com/condition/chronic-urticaria#CONSULTATION_AND_REFERRAL.
- A pediatrist should be consulted, as necessary, regarding chronic urticaria in a child.
References
- Weinberger M. Evidence-based considerations regarding the US and international guidelines for chronic urticaria. J Allergy Clin Immunol Pract 2018;6(6):2174. [PubMed]
- Cornillier H, Giraudeau B, Munck S ym. Chronic spontaneous urticaria in children - a systematic review on interventions and comorbidities. Pediatr Allergy Immunol 2018;29(3):303-310. [PubMed]
- Zuberbier T, Aberer W, Asero R ym. The EAACI/GA²LEN/EDF/WAO guideline for the definition, classification, diagnosis and management of urticaria. Allergy 2018;73(7):1393-1414. [PubMed]