Hives

Also known urticaria, weals or wheals

Hives are an itchy rash that can appear anywhere on your body. This rash comes and goes and can last from hours or days (acute) to months (chronic).

Key points

  1. Hives are common, with 1 out of 5 people getting them at some stage in their life. 
  2. Hives can be triggered by lots of things and the cause can only be identified about half the time.
  3. Treatment involves avoiding known triggers and taking antihistamines. 
  4. Angioedema is similar to hives, but the swelling is beneath your skin.

Are hives serious?

Hives usually settle within a day and cause no harm. However, they can sometimes be a sign of a serious allergic reaction, drug reaction or even life-threatening anaphylaxis

Seek medical help immediately by calling 111 in New Zealand if you have: 

  • a rash within 20 minutes of eating or taking a new medicine, OR
  • swelling of your lips, mouth or airway making it hard to breathe.



Image source: DermNet NZ

What causes hives?

Hives form when your immune system releases a chemical called histamine. Histamine release can be triggered by lots of things and the cause is not always clear. 

  • Infection from a virus is the most common cause of hives in children, especially if they last for more than 24 hours.
  • Direct contact with plants or animals may cause hives in just one area of your body.
  • Allergic reactions to food, medicines or insect stings can appear as hives. They usually occur within 1–2 hours of exposure and disappear in most cases within 6-8 hours.
  • Hives can be caused by physical triggers, including cold (such as cold air, water or ice), heat, sunlight (solar), vibration, rubbing or scratching your skin (dermatographism) and delayed pressure (such as after carrying heavy bags).
  • Rarely, exercise, sweating, alcohol, spicy food or coffee may cause hives.
  • Stress rarely causes hives but may make symptoms worse.

Identifying the cause of hives is tricky. They are probably due to an allergic reaction if there are patterns to when they appear, eg: 

  • always within 2 hours of a meal
  • other symptoms occur around the same time, such as stomach pain, vomiting, difficulty breathing or dizziness.

Ongoing hives lasting days at a time are almost never due to allergy, with the exception of some cases of allergy to medicines.

Serious allergic reaction

Sometimes hives may be a sign of a serious, life-threatening allergic reaction which requires immediate medical attention. If hives occur with swelling of your tongue or throat, difficulty breathing or low blood pressure, anaphylaxis should be suspected. You will need urgent administration of adrenaline (Epipen®) and medical assessment. 

What are the different types of hives?

There are 2 main types of hives: 

  • Acute urticaria (hives) – these last less than 6 weeks. It often goes away within hours to days.
  • Chronic urticaria (hives) – this is when hives occur most days for more than 6 weeks.

This page focuses on acute cases of hives. Read about chronic hives. 

What are the symptoms of hives?

The key symptoms of hives are weals (raised, itchy swellings) that:

  • are round or form rings, a map-like pattern or giant patches
  • may change shape
  • are a few millimetres or several centimetres in diameter
  • coloured white or red
  • with or without a red flare
  • may last a few minutes or several hours
  • can affect any part of your body
  • may be widespread across your skin.

How are acute hives diagnosed?

For most cases of acute hives, you don't need to see a doctor.

  • If you notice a trigger causes you to get hives, try to avoid it.
  • Avoid anything that may worsen hives, such as heat, tight clothes and alcohol. 
  • Most people with acute  hives do not need tests, unless they go on for a long time or you have unusual symptoms around the same time.
  • If the suspected cause is allergy, skin or blood tests may be done.

How are hives treated? 

Cool cloth, bath or shower

If the reaction is mild, simple measures such as a cool bath or shower may be all that is needed. 

Antihistamines

Since the skin reaction is caused by histamine release, most people benefit from taking antihistamines such as loratadine or cetirizine to ease the itch. They can be bought from a pharmacy or prescribed by a doctor or nurse practitioner.

Please note these medicines may cause drowsiness, so take care when driving or operating machinery. 

Avoid the causes/triggers

If the cause is a specific food, food additive, shellfish, cosmetic or anything else, avoiding these foods or substances will reduce the risk of hives coming back again.

Also avoid anything that can make hives worse such as excessive heat, spicy foods or alcohol. 

Aspirin and other NSAIDs should be avoided as they often make symptoms worse.

Severe cases

If the rash is widespread or you have any swelling of your mouth or airways, seek medical help urgently. You may need need adrenaline, steroid medicine and admitting to hospital to identify the cause and prevent life-threatening reactions.  

Diet

Special diets aren’t usually useful in the management of hives.

Learn more

Images of urticaria & angioedema DermNet NZ
Allergies & hives (urticaria & angioedema) WebMD

References 

  1. Hives (urticaria) Australasian Society of Clinical Immunology and Allergy (ASCIA), 2019
  2. Acute urticaria DermNet NZ
  3. Diagnosing urticaria NHS, UK

Reviewed by

Dr Sharon Leitch is a general practitioner and clinical research training fellow in the Department of General Practice and Rural Health at the University of Otago. Her area of research is patient safety in primary care and safe medicine use.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Sharon Leitch Last reviewed: 22 Feb 2020