Hives (urticaria)

Have you ever broken out in a pink or red rash with raised bumps or small welts on your skin? It may have been hives, also known as 'urticaria'.

But what, exactly, is this rash? And what causes it to break out? We explore hives, with tips and insights, plus advice on when to seek medical attention.

Hives are a skin rash that occurs when your body produces the chemical histamine. The rash can also occur as a result of an allergic reaction, an infection, an immune system condition or even the dye that's used during radiological tests.¹

"It's estimated that one in 5 people will develop hives at some time in their life.² But the cause is not always clear, which can be frustrating," says Dr Mahila Namasivayam, Paediatric Clinical Allergy and Immunology Specialist.

According to Dr Namasivayam, hives usually appear as an itchy red or pink rash on your skin, either with raised bumps or small welts, and sometimes with a central white area that's surrounded by a red flare.

"It can change shape [and] vary in size," she says. "It can be small, like the head of a pin, or quite big. It can be irregular, like a map, or round, or oval. And they're typically quite itchy."

The rash can appear anywhere, including your face, extremities, chest or back. It can also spread to other parts of your body.

"If it's in the deeper tissues under the skin, then the inner lining of [for instance] the nose, mouth or lips can get swollen," Dr Namasivayam adds.

While the rash will usually disappear within a day, hives can stick around for a few days or even weeks.

Most of the time, it's unclear what causes a hives breakout. However, some known factors include:

• infections
• allergic reactions (such as certain foods or animals)
• coming into contact with certain animals or plants
• insect bites or stings
• certain medications (including antibiotics, aspirin or codeine)
• certain food additives
• underlying health conditions (such as hepatitis or rubella)
• stress
• extreme temperatures
• physical exertion.³

"In children, we find that one of the most common causes is viral infection, especially if the hives last longer than 24 hours," says Dr Namasivayam.

"Typically, if it's a food allergy, we find that as the child is eating the food, it'll start around their mouth and then spread out."

"If it's a pet allergy, it tends to be on the area where the [pet] licked."

While hives themselves generally aren't dangerous, they may be symptomatic of a more serious problem that might require medical attention. So, it's important to be aware of any other accompanying symptoms.

For instance, if you or a loved one also experience swelling in the tongue or throat, trouble breathing or lowered blood pressure, it may be anaphylaxis, which requires urgent medical attention.²

Hives-like symptoms might also point to something that's not hives at all, like a more serious auto-immune condition.

"There are other conditions where things that look like hives are not really. Things like lupus can present like that," says Dr Namasivayam.

Here, you should be vigilant of accompanying symptoms like bruising, sore joints and a high fever, which will require urgent medical attention.

You might also consider seeing a doctor if your hives are interfering with your work, school or sleep, or if the rash lasts longer than 6 weeks (chronic urticaria).

If you're considering asking your doctor to test for hives, it's a good idea to take a quick photo of your rash while it's visible.

"Nowadays, everyone's got a camera on their phone. It's nice to actually look at the rash and confirm that it is what it is," says Dr Namasivayam.

While testing is usually not required for hives, your doctor may do a skin prick or blood test if they suspect something more serious. From there, treatment will come down to addressing the cause of the hives.

If you have hives, Dr Namasivayam recommends avoiding a few things that can make the rash worse. These include:

• extreme heat or cold
• spicy food
• alcohol
• stress
• non-steroidal anti-inflammatory medicines (NSAIDs), including aspirin and ibuprofen.

"And if you know what the allergen is, obviously minimise that in your environment," Dr Namasivayam adds.

Likewise, things you may do to help your hives include:

• wearing lose, breathable clothing
• using a soothing lotion
• ensuring your skin isn't too dry
• taking antihistamines
• managing stress, which can make hives worse
• in more extreme cases, taking oral or topical steroids.

If hives are a reoccurring thing for you or your loved one, Dr Namasivayam recommends keeping a record of things like your environment, what you're wearing and what you've recently had to eat and drink, to help narrow down any potential causes.

Allergy and Anaphylaxis Australia has online support resources available. You can also call for help and support on 1300 728 000.

The Australasian Society of Clinical Immunology and Allergy (ASCIA) offers information and support for Australians and New Zealanders living with allergies, providing medical practice, training, education and research.