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 skin-coloured or pale swellings on the surface of your skin, usually surrounded by redness. They are usually very itchy and may have a burning sensation.
  2. Hives are common with 1 out of 5 people getting them at some stage in their life. In 4 out of 5 adults, hives are not due to allergy.
  3. A cause or trigger can only be identified about half the time.
  4. Angioedema is similar to hives, but the swelling occurs beneath your skin instead of on the surface. Read more about angioedema
  5. Treatment of hives involves avoiding the trigger if one is known and taking antihistamines. 

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
  • rapid swelling of your lips, mouth or airway making it hard to breathe.



Image source: DermNet NZ

What causes hives?

Hives are rarely due to a serious underlying disease. They form when your immune system releases a chemical called histamine. Histamine release can be triggered by a range of factors 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.
  • A reaction caused by 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.
  • In some people, hives are caused by physical triggers, including cold (such as cold air, water or ice), heat, sunlight (solar), vibration, rubbing or scratching of your skin (dermatographism) and delayed pressure (such as after carrying heavy bags).
  • In other people, exercise, sweating, alcohol, spicy food or coffee may cause symptoms.
  • Stress is a very rarely the cause of hives but may make the 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
  • when symptoms involving other organs 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, that last a few hours, you don't need to see a doctor.

  • If you notice a trigger that causes you to get hives, then try to avoid this.
  • Also 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 non-sedating antihistamines such as loratadine or cetirizine to ease the itch.

Although referred to as 'non-sedating', these medicines may still cause drowsiness in some people, so take care when driving or operating machinery. These medicines can be brought from a pharmacy or prescribed by a doctor or nurse practitioner. 

Avoid the causes/triggers

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

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

Severe cases

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

Avoid

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

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
Credits: Health Navigator Editorial Team.