Hives are raised, itchy welts that can suddenly appear on the skin. They are also known as urticaria.

The welts can vary in size and shape and may appear anywhere on the body. They often disappear from one area and then develop somewhere else.

Urticaria can occur because of an allergic reaction, infection, medicine or physical trigger. However, sometimes no obvious cause can be identified.

Most episodes are mild and temporary. In some cases, though, a skin reaction may occur as part of a severe allergic reaction called anaphylaxis.

What Do Hives Look Like?

The rash usually appears as raised patches or welts.

They may be:

• pink, red or skin-coloured
• intensely itchy
• round or irregular in shape
• small or several centimetres wide
• surrounded by redness
• present in one area or across the body

Individual welts often disappear within hours. However, new ones can continue to develop in other areas.

What Causes Urticaria?

The rash develops when cells in the skin release chemicals such as histamine.

Possible triggers include:

• foods
• medicines
• insect bites or stings
• viral or bacterial infections
• pollen
• animal dander
• latex
• heat
• cold
• pressure on the skin
• exercise
• stress

In many cases, particularly when symptoms continue for a long time, doctors cannot identify a specific trigger.

Acute and Chronic Urticaria

Doctors generally classify the condition according to how long symptoms continue.

Acute Urticaria

Acute symptoms last for less than 6 weeks.

Possible triggers include:

• infections
• allergic reactions
• medicines
• certain foods
• insect bites or stings

Many acute episodes settle within hours or days.

Chronic Urticaria

Chronic urticaria lasts or repeatedly returns for more than 6 weeks.

A simple allergy does not cause most chronic cases. Instead, immune system activity may contribute, and sometimes no clear cause can be found.

If you experience repeated episodes for more than 6 weeks, speak with your doctor.

Food Allergies and Skin Reactions

An itchy raised rash can occur during a food allergy.

Common food allergens include:

• peanuts
• tree nuts
• eggs
• milk
• shellfish
• fish
• sesame
• wheat
• soy

Food allergy may also cause swelling, vomiting, wheezing or breathing difficulties.

For more information, see our Food Allergies guide.

The Australasian Society of Clinical Immunology and Allergy also provides information about food allergy and allergic reactions.

Hayfever and Other Allergies

People with one allergic condition may also experience other types of allergy.

For example, someone with hayfever may react to pollen, dust mites, mould or animal dander.

However, having hayfever does not automatically mean that an episode of urticaria has the same trigger.

For more information about seasonal and environmental allergies, see our Hayfever guide.

Can Medicines Cause Hives?

Yes. Some medicines can trigger an allergic skin reaction.

Possible examples include:

• antibiotics
• anti-inflammatory medicines
• some pain-relieving medicines
• certain blood pressure medicines

However, a rash that develops while taking medicine is not always an allergy.

If symptoms start after a new medicine, contact your doctor or pharmacist for advice.

Do not stop an important prescribed medicine without professional advice unless you are experiencing a severe allergic reaction that requires emergency treatment.

Infections and Urticaria

Viral and bacterial infections can also trigger raised itchy welts.

This is particularly common in children.

A rash may appear during an infection or shortly afterwards, even when there has been no exposure to a new food or medicine.

Seek medical advice if the rash occurs with significant fever, severe illness or other concerning symptoms.

Physical Triggers

Some people develop symptoms after specific physical triggers.

These can include:

• cold temperatures
• heat
• sweating
• sunlight
• pressure
• exercise
• vibration

Keeping a diary of your symptoms may help identify patterns.

Record:

• what you were doing before symptoms appeared
• foods you had eaten
• medicines you had taken
• recent illness
• temperature or environmental exposure

Can Stress Trigger Symptoms?

Stress does not cause every episode, but it may trigger or worsen symptoms in some people.

Stress can influence the immune system and may also make itching feel more noticeable.

If you notice a link between stress and flare-ups, stress-management strategies may help alongside appropriate medical treatment.

Hives and Swelling

Urticaria can sometimes occur with deeper swelling called angioedema.

Angioedema commonly affects:

• lips
• eyelids
• face
• hands
• feet

Mild swelling may settle without treatment.

However, swelling of the tongue, throat or airway requires urgent medical attention.

Hives or Anaphylaxis?

An itchy skin rash on its own is usually not life-threatening.

However, if the rash occurs with other serious allergy symptoms, the person may be experiencing anaphylaxis.

Warning signs include:

• difficult or noisy breathing
• swelling of the tongue
• swelling or tightness in the throat
• wheezing
• persistent coughing
• difficulty speaking
• dizziness
• collapse

If anaphylaxis is suspected, call 000 immediately.

If the person has a prescribed adrenaline injector, use it according to their ASCIA Action Plan.

Do not wait to see whether symptoms improve.

How Is the Condition Diagnosed?

A doctor can often recognise urticaria by examining the skin and discussing the pattern of symptoms.

They may ask about:

• foods recently eaten
• new medicines
• recent infections
• insect bites
• exercise
• heat or cold
• stress
• how long individual welts last
• how often the rash returns

Allergy testing is not necessary for every person with an episode of urticaria.

However, further investigation may be useful if a particular allergic trigger is strongly suspected or symptoms are chronic.

Treatment

Treatment depends on the severity, duration and likely cause.

Mild symptoms may settle on their own.

Management may include:

• avoiding a confirmed trigger
• taking an appropriate antihistamine
• applying a cool compress
• wearing loose clothing
• avoiding excessive heat
• avoiding scratching

Your pharmacist can recommend an appropriate treatment based on your symptoms, age, medical conditions and other medicines.

Antihistamines

Antihistamines block the effects of histamine and can reduce itching and welts.

Non-drowsy antihistamines are often preferred during the day.

However, some products may still cause drowsiness in certain people.

Ask your pharmacist for advice, particularly if you:

• need to drive
• operate machinery
• are pregnant or breastfeeding
• are treating a child
• take other medicines

Are Steroid Creams Helpful?

Steroid creams generally do not work well for ordinary urticaria because the reaction develops deeper within the skin.

However, topical steroids may help if another inflammatory skin condition is also present.

Do not use strong steroid creams unless a healthcare professional recommends them.

How to Relieve Itching

Simple measures can improve comfort while symptoms settle.

You can try:

• using a cool compress
• taking a cool or lukewarm shower
• wearing loose cotton clothing
• keeping the room cool
• avoiding hot baths
• avoiding scratching

Heat can make itching worse for some people.

Hives in Children

Children commonly develop episodes of urticaria, often during or after viral infections.

The welts can appear suddenly, disappear and then develop somewhere else.

Seek medical advice if your child:

• has symptoms that persist
• develops significant swelling
• appears very unwell
• has severe abdominal pain
• develops the rash after starting a new medicine

Call 000 immediately if there is difficulty breathing, tongue swelling, throat swelling or collapse.

During Pregnancy or Breastfeeding

Some antihistamines may be suitable during pregnancy or breastfeeding.

However, not every product is appropriate.

Speak with your pharmacist, GP or maternity healthcare professional before starting treatment.

How Long Do Symptoms Last?

Individual welts often disappear within several hours.

However, new ones may continue to develop.

Acute episodes usually settle within days or a few weeks.

If symptoms continue or repeatedly return for more than 6 weeks, doctors classify the condition as chronic urticaria.

Persistent symptoms should be medically assessed.

When Should You See a Doctor?

Arrange medical assessment if:

• symptoms are severe
• episodes repeatedly return
• symptoms continue for several days without improvement
• the condition lasts for more than 6 weeks
• swelling is significant
• symptoms began after taking a new medicine
• you cannot identify the cause
• over-the-counter treatment is not helping

You can also find general information about urticaria through Healthdirect.

When Is It an Emergency?

Call 000 immediately if a skin reaction occurs with:

• difficulty breathing
• swelling of the tongue
• throat swelling or tightness
• wheezing
• difficulty speaking
• dizziness
• collapse
• rapidly worsening symptoms

These may indicate anaphylaxis.

How to Help Prevent Future Episodes

If you know your trigger, avoiding it may help reduce future episodes.

Helpful measures may include:

• avoiding confirmed food allergens
• keeping an accurate record of medicine allergies
• avoiding known physical triggers
• preventing overheating where relevant
• managing environmental allergies
• keeping a symptom diary
• managing stress

However, do not unnecessarily remove important foods or stop prescribed medicines without professional advice.

Speak With Your Pharmacist

Your MediAdvice pharmacist can help assess mild symptoms and recommend appropriate treatment.

They can also provide advice about:

• antihistamines
• possible medicine reactions
• allergy triggers
• treatment for children
• when you should see a doctor

If symptoms suggest anaphylaxis or another severe allergic reaction, seek emergency medical care immediately.

General advice only: This information is not intended to replace advice from your healthcare professional. If symptoms are severe, persistent or worsening, or you develop difficulty breathing or swelling of the tongue or throat, call 000 immediately.