Hives (mate kārawa) are an itchy rash that can appear anywhere on your body. This rash is sometimes called weals or wheals. It comes and goes and can last from hours or days (acute) to months (chronic).
Hives are common, with 1 out of 5 people getting them at some stage in their life.
Hives can be triggered by lots of things and the cause can only be identified about half the time.
Treatment involves avoiding known triggers and taking antihistamines.
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.
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.
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.
Special diets aren’t usually useful in the management of hives.
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
What are chronic hives?
Chronic hives (urticaria) are when hives occur most days for more than 6 weeks. They are less common than acute hives, with about 1 in 1000 people affected.
They are more common in women than men (two-thirds of those with this condition are women).
Symptoms are the same as in acute hives, but last longer.
Although chronic hives clear up in most cases, some people will experience longer-term symptoms.
Treatment includes avoiding any known triggers and taking antihistamines.
What are the different types of chronic hives?
Chronic hives may be spontaneous or inducible (physical). You can have both types at the same time.
Spontaneous chronic urticaria is the diagnosis when the trigger for hives is not known.
Inducible or physical chronic urticaria is a reaction to a known external factor. This includes hives caused by the following:
stroking your skin (dermographism) – this is the most common type of inducible/physical urticaria
exposure to cold, cold water and cold objects (cold urticaria)
sweating (cholinergic urticaria)
direct contact with a substance such as stinging nettles, foods, preservatives, fragrances, plant and animal products, metals and rubber latex (contact urticaria) – this is different to dermatitis, which develops hours or days later
pressure to your skin – this can be an immediate or delayed reaction (pressure/delayed pressure urticaria)
exposure to sunlight or to artificial ultraviolet (UV) light (solar urticaria)
direct contact of warmth to your skin (heat urticaria)
exposing your skin to vibration, repetitive stretching or rubbing (vibratory urticaria)
contact with water (aquagenic urticaria).
Some of these types are quite rare.
What causes chronic or recurrent hives?
While external factors can be identified as triggers for inducible/physical hives, the cause of chronic spontaneous hives is often unknown, but it is likely to be an autoimmune reaction (where your immune system mistakenly attacks your own cells as if they were cells from a germ).
Chronic spontaneous hives have also been associated with:
Chronic hives are diagnosed if you have a long history (more than 6 weeks) of daily or regular hives. Your doctor will take a family history and do a physical examination.
Inducible hives are often confirmed by inducing the reaction, such as scratching your skin in dermographism or applying an ice cube in suspected cold urticaria.
Your doctor may ask for blood tests to rule out underlying conditions.
How are chronic hives treated?
Most people with chronic hives manage with appropriate doses of non-drowsy antihistamines such as cetirizine and loratadine. The doses for chronic hives are usually higher than the usually recommended doses. Although referred to as 'non-sedating', these medicines may still cause drowsiness especially at higher doses, so take care when driving or operating machinery.
If the cause is a specific food, food additive, shellfish, cosmetic or something else, avoiding those 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.
Steroid or antihistamine creams are not helpful and may cause skin changes or skin irritation.
People with severe symptoms interfering with quality of life may be referred to a clinical immunology/allergy specialist or dermatologist for assessment and consideration of additional medications.
What is the outlook for chronic hives?
Although chronic hives clear up in most cases, 15% of people continue to have symptoms at least twice weekly after 2 years.
Urticarial weals can be a few millimetres or several centimetres in diameter, coloured white or red, with or without a red flare. Each weal may last a few minutes or several hours and may change shape. Weals may be round, or form rings, a map-like pattern or giant patches.
Urticaria can affect any site of the body and tends to be distributed widely.
Angioedema is more often localised. It commonly affects the face (especially eyelids and perioral sites), hands, feet and genitalia. It may involve tongue, uvula, soft palate or larynx.
Serum sickness due to blood transfusion and serum sickness-like reactions due to certain drugs cause acute urticaria leaving bruises, fever, swollen lymph glands, joint pain and swelling.
In chronic inducible urticaria, weals appear about 5 minutes after the stimulus and last a few minutes or up to one hour.
Characteristically, weals are:
Linear in symptomatic dermographism
Tiny in cholinergic urticaria
Confined to contact areas in contact urticaria
Diffuse in cold urticaria—if large areas of skin are affected, they can lead to fainting (potentially dangerous if swimming in cold water).
The weals are more persistent in chronic spontaneous urticaria, but each has gone or has altered in shape within 24 hours. They may occur at certain times of the day.
This information is from Auckland HealthPathways Urticaria accessed December 2019
Any features suggestive of urticarial vasculitis (UV) – a single urticarial lesion that lasts longer than 24 hours and may leave bruising or scarring.
Check for signs and symptoms of severe or life-threatening allergic reaction.
Well-circumscribed itchy weals with central pallor and surrounding flare that resolve within 24–48 hours without marking the skin.
Rule out other causes of itchy rash.
Routine diagnostic measures are not recommended in urticaria.
Do not request "routine allergy testing" or "allergy panels" – test only if clinical history strongly suggests a specific trigger.
Non-sedating antihistamines are first-line treatment in both acute and chronic urticaria. High doses are often required to control symptoms. Treatment failure is most commonly due to inadequate doses taken irregularly, or for too short a duration.