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Medical Dermatology

Urticaria (Hives)

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Dr. Liew Hui Min

Urticaria, commonly known as hives, is a skin reaction that causes raised, red, itchy welts of various sizes to appear on the surface of the skin. These welts occur when certain cells release histamine and other chemicals into the bloodstream, causing small blood vessels to leak fluid into the skin. Urticaria can develop anywhere on the body and may appear suddenly. The condition can be acute (lasting less than six weeks) or chronic (persisting beyond six weeks), with episodes that may last hours or days before fading.

Symptoms Causes Types Diagnosis Treatment Prevention FAQ
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Symptoms
Causes
Types
Diagnosis
Treatment
Prevention
FAQ

Symptoms of Urticaria

Urticaria presents with various visible and physical symptoms that can vary in intensity. Common symptoms include:

  • Raised welts or wheals: These red or skin-coloured bumps have clearly defined edges and can range in size from a few millimetres to several centimetres. They may appear anywhere on the body and often change shape, disappear, and reappear within hours.
  • Intense itching: A common symptom is severe itching in the affected areas, which can be particularly disruptive at night, potentially affecting sleep quality.
  • Angioedema: In some cases, deeper swelling may occur beneath the skin, especially around the eyes, lips, hands, feet, or genitals. This swelling tends to cause discomfort rather than itching and may take longer to resolve than surface hives.
  • Skin colour changes: Once the welts fade, the skin may temporarily appear reddish or show slight discolouration, which typically resolves over time.

Causes and Risk Factors

Urticaria can be triggered by a wide range of factors, which vary from person to person. Common causes include:

  • Allergic reactions

    Exposure to certain foods (nuts, shellfish, eggs), medications (antibiotics, NSAIDs), insect stings, or latex can trigger an immune response resulting in hives. The reaction typically occurs soon after exposure to the allergen.

  • Physical triggers

    Some individuals develop hives in response to physical stimuli such as pressure, cold, heat, sunlight, water, vibration, or exercise. These reactions are often predictable when the specific trigger is known.

  • Infections

    Viral infections, bacterial infections, and parasitic infestations can trigger urticaria as part of the body’s immune response. Common triggers include upper respiratory infections, streptococcal infections, and hepatitis.

  • Underlying medical conditions

    Autoimmune disorders like thyroid disease, lupus, or rheumatoid arthritis may be associated with chronic urticaria. The hives develop as part of the dysregulated immune response.

  • Stress

    Emotional or physical stress may contribute to the onset or exacerbation of hives. Stress may lead to an inflammatory response in the body, triggering skin reactions.

  • Idiopathic causes

    In many cases of chronic urticaria, no specific cause can be identified despite extensive evaluation. These cases are termed idiopathic chronic urticaria.

Types of Urticaria

Acute urticaria

Lasting less than six weeks, acute urticaria is often triggered by food allergens, medications, or infections. It typically resolves when the trigger is removed or treated and responds well to antihistamines.

Chronic urticaria

When hives persist or recur for over six weeks, it is classified as chronic. Often with no clear cause, it may be linked to autoimmune processes. Chronic urticaria can significantly affect daily routines and may require long-term management. Episodes may occur daily for months or years.

Physical urticarias

Triggered by physical stimuli, these include dermographism (writing on the skin), cholinergic urticaria (heat/exercise), cold urticaria, solar urticaria (sunlight), aquagenic urticaria (water), and delayed pressure urticaria.

Contact urticaria

This form develops when a substance touches the skin through immunologic or non-immunologic mechanisms. Triggers include foods, latex, preservatives, or chemicals in cosmetics. Reactions are typically localised but can spread.

Angioedema

Some individuals experience angioedema (deep tissue swelling) without the typical hives. It may be hereditary or acquired, often involving complement protein deficiencies, and may require specialised treatment.

Diagnostic Methods

Clinical evaluation: Diagnosis starts with a detailed medical history and physical examination. The appearance, distribution, and duration of lesions are assessed, focusing on characteristic wheals that blanch with pressure and resolve within 24 hours. Patterns of recurrence and associated symptoms offer valuable diagnostic information.

Skin tests: If an allergic reaction is suspected, skin tests such as prick tests or allergy blood tests can help identify sensitivities to specific substances. For physical urticarias, challenge tests may be performed, like exposure to cold for cold urticaria or light for solar urticaria, to trigger and confirm the diagnosis.

Blood tests: Blood tests may be conducted to rule out underlying conditions or infections that could be contributing to the hives. Common tests include a complete blood count, thyroid function panels or autoantibody screening if an autoimmune or systemic issue is suspected.

Treatment Options

Management of urticaria focuses on symptom control, identifying and avoiding triggers, and addressing any underlying causes when possible.

Antihistamines

These are the first-line treatments for urticaria. By blocking histamine receptors, antihistamines help reduce itching and swelling. Non-sedating antihistamines are commonly preferred to avoid drowsiness while providing effective relief.

Corticosteroids

For more severe cases, oral or topical corticosteroids can help reduce inflammation and control swelling. However, long-term use is generally avoided due to the risk of side effects, such as skin thinning or increased susceptibility to infections.

Leukotriene receptor antagonists

These medications block leukotrienes, chemicals that contribute to inflammation and hives, particularly in chronic cases. They are often used as an adjunct to other treatments to control symptoms.

Omalizumab (Xolair)

A biologic medication that may be used for chronic urticaria that does not respond to other treatments. It works by targeting IgE antibodies, which are involved in allergic reactions, to reduce symptoms and prevent flare-ups.

Prevention and Management

While it may not be possible to prevent urticaria entirely, identifying and avoiding triggers can significantly reduce flare-ups. Managing stress, maintaining a cool environment, and following prescribed treatments are necessary for controlling symptoms. Regular use of antihistamines and other medications can help manage chronic hives, while avoiding physical triggers, such as tight clothing or temperature extremes, can prevent attacks. Keeping a symptom diary can help identify personal triggers and guide management.

Frequently Asked Questions

What is the difference between urticaria and an allergic rash?

Urticaria appears as raised welts that change shape and typically fade within 24 hours. In contrast, allergic rashes like eczema or contact dermatitis last longer and often cause persistent redness, dryness, and scaling.

Does urticaria always itch?

Most cases of urticaria cause intense itching, but some people may experience only mild irritation or no itching at all, especially in cases involving angioedema, where swelling is the primary symptom.

Can urticaria worsen over time?

If left untreated or poorly managed, urticaria can become more frequent or severe, particularly if the underlying trigger remains unidentified or unresolved.

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Dr Liew Hui Min

Dr. Liew Hui Min is an accredited consultant dermatologist from the Ministry of Health and the General Medical Council UK.

Her clinical interest includes:

  • Paediatric Dermatology,
  • Women’s Dermatology,
  • General Adult Dermatology.

Having trained in major London Hospitals, Dr Liew returned to Singapore in 2014 as a Consultant at KK Women’s and Children’s Hospital (KKH) where she specialised in paediatric, women, obstetric and vulva dermatology. Currently, Dr Liew practices at HM Liew Skin & Laser Clinic located at Gleneagles Hospital.

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