Urticaria
Also known as Hives, Nettle rash
This article is general health information for the selected condition. It is not a diagnosis and does not replace clinical judgement. If you have questions or need treatment advice, please consult a qualified healthcare professional.
What is urticaria?
Urticaria is an itchy raised rash caused by histamine release from mast cells in the skin. Individual weals characteristically appear and disappear within 24 hours, moving around the body. Acute urticaria often follows infection, whereas chronic urticaria lasting over six weeks is usually spontaneous rather than allergic.
Causes
- Viral infection, the commonest trigger of acute urticaria
- Autoimmune mast cell activation in chronic spontaneous urticaria
- Medicines including NSAIDs, opioids and antibiotics
- Food allergy in a minority of acute cases
- Physical triggers such as pressure, cold or exercise
- Insect stings
Symptoms
- Raised itchy weals that blanch with pressure
- Individual lesions lasting under 24 hours
- Weals moving to different body areas
- Deeper swelling of lips or eyelids in angioedema
- Burning or stinging sensation
- Symptoms often worse in the evening
Risk factors
- Female sex for chronic urticaria
- Existing autoimmune thyroid disease
- Recent viral illness
- Regular NSAID use
- Atopic background
Diagnosis
- Clinical diagnosis from the appearance and fleeting nature of weals
- Duration to classify acute versus chronic
- Limited blood tests including full blood count and inflammatory markers
- Thyroid antibodies in chronic cases
- Allergy testing only when a clear temporal trigger exists
- Skin biopsy if individual lesions last beyond 24 hours
Treatment
- Non sedating antihistamines, often at increased doses
- Adding a second antihistamine or leukotriene antagonist
- Omalizumab for antihistamine resistant chronic urticaria
- Short corticosteroid courses only for severe acute flares
- Avoiding identified triggers including NSAIDs
- Adrenaline autoinjector where anaphylaxis has occurred
Self care
- Take non sedating antihistamines regularly rather than only when itchy
- Keep cool, since heat worsens itching
- Wear loose cotton clothing
- Avoid anti inflammatory painkillers, which commonly aggravate hives
- Use cool compresses or calamine for comfort
- Keep a diary of possible triggers
- Avoid scratching, which prolongs weals
When to see a doctor
Book an appointment if:
- Hives lasting more than six weeks
- Symptoms not controlled on standard antihistamine doses
- Individual weals lasting more than 24 hours or leaving bruising
- Hives with joint pain or fever
- Significant impact on sleep or daily life
- Recurrent deep swelling of the lips or eyelids
Some symptoms need emergency care rather than an appointment. See the warning signs listed above.
Prevention
- Identify and avoid confirmed triggers
- Avoid anti inflammatory painkillers if these aggravate hives
- Take antihistamines regularly during active phases
- Manage stress, which can worsen chronic urticaria
- Carry an adrenaline autoinjector if anaphylaxis has occurred
Outlook
Acute urticaria usually resolves within days to weeks. Chronic spontaneous urticaria typically lasts one to five years and then remits in most people. Symptoms are controllable in the large majority with antihistamines, sometimes at higher than standard doses, and omalizumab is highly effective for resistant cases.
Common questions
Is chronic urticaria caused by food allergy?
Rarely. Chronic spontaneous urticaria is usually driven by autoimmune mast cell activation, not diet. Extensive food elimination is generally unhelpful and can cause nutritional harm.
When is it an emergency?
Swelling of the tongue or throat, difficulty breathing or swallowing, wheeze, dizziness or collapse suggest anaphylaxis and require immediate adrenaline and emergency services.
Why are higher antihistamine doses used?
Guidelines support increasing non sedating antihistamines up to four times the standard dose for chronic urticaria before moving to other treatments. This should be done on medical advice.
References
Important: Dard AI is not a medical device and does not diagnose, treat, or replace clinician judgement. This article is general information only. Always consult a qualified healthcare professional about diagnosis and treatment, and seek emergency care for severe or rapidly worsening symptoms.