​We all get minor itchy skin irritation and rashes from time to time. 

In Singapore, most of us would say they’re caused by mosquitos, the hot weather and sweat. But if you’re noticing clusters of raised, itchy red bumps that suddenly appear on your skin, take note.

Hives (urticaria) and angioedema

“Hives (also known as urticaria) are pink or pale red swellings on the skin. They are usually itchy but can also be burning or stinging. They can appear anywhere on the body and are often round or ring shaped. These skin lesions may change in size, fade and reappear. Individual skin lesions typically resolve within 24 hours without a trace,” explained Clinical Associate Professor Pang Shiu Ming, Senior Consultant from the Department of Dermatology at Singapore General Hospital (SGH), a member of the SingHealth group.

“Angioedema causes deeper swellings in the skin, affecting the eyelids, lips or tongue. Generally lasting longer than hives, it (angioedema) may persist for 1-2 days.

Some people may have either hives (urticaria) or angioedema, but it’s also possible to have both,” Dr Pang added.

The main difference between the two conditions is that angioedema causes deeper swelling of skin or mucous membranes. Mucous membranes are the thin layer of mucous or phlegm inside your organs and body. We’ll talk more about angioedema later on.

Hives (urticaria): What causes them?

Hives form because of histamines. Histamines aren’t bad - they’re chemicals that regulate your body’s response to foreign substances and injury. Overreaction gives allergy symptoms.

50% of acute urticaria has no known cause. Urticaria may happen because of viral infections (cold, flu) in your breathing system, drugs, food, touching plants, animals, or chemicals. As you can see, there are many types of triggers.

Diagram reproduced from the Textbook of Dermatology.

Types of hives (urticaria): Acute and chronic

The two main types of hives include acute and chronic hives.

Chronic hives: How to prevent

There are 2 types of chronic urticaria - inducible (also called physical urticaria in the past) and chronic spontaneous urticaria (CSU).

Type 1: Inducible (previously known as physical urticaria)

Inducible urticaria is caused by physical stimulus, also known as triggers. Your doctor will diagnose it with the physical stimuli by simulating the triggers. 

It’s really important to find out what causes your inducible urticaria, because you can remove or prevent the trigger. That’s the best way to prevent inducible hives.

What kinds of inducible urticaria do most people have?

• Dermographism (most common)

• Cold urticaria (second-most common)

• Cholinergic (third-most common)

• Solar (less common)

• Vibration (less common)

• Delayed-pressure (less common)

How to prevent inducible hives:

What causes hives rash? You’ll already know that you may develop hives after being exposed to your triggers. When you find out what these triggers are, you can avoid them. It’ll really help you with hives prevention.

1) Skin Pressure /friction

Do you notice hives after wearing tight clothes? You may have dermographism (skin writing) or  delayed-pressure urticaria.

Putting pressure on your skin for a long time can cause delayed-pressure urticaria. You may notice that you get hives with tight clothes, bag strap abrasion, friction from jewellery rubbing against your skin, and sitting down for a long time.

Use these tips to stop it from happening:

• Wear loose-fitting clothes made of breathable material.

• Carry backpacks with padded straps to lessen friction and spread out the weight evenly on your body.

• Don’t wear jewellery like necklaces and bracelets that rub against your skin.

• Wear singlets or camisoles to prevent the inside seams of your clothes from scratching or rubbing your skin.

• Don’t wear clothes with tight elastic waistbands.

• Don’t sit down for too long. Stand up and walk around every 20 minutes. 

2) Cold temperatures

Staying in a cold place or touching ice may increase your risk of getting cold hives. It’s best not to exercise in cold winds or swim in cold water when you’re travelling overseas.

We don’t usually get cold weather here in Singapore, but you should still wear a jacket or cover your skin in air-conditioned places, like shopping malls and your office.

3) Heat

On the other hand, heat is something we’re very familiar with in Singapore. Heat is a common trigger for cholinergic urticaria (hives caused by high body temperature) in Singapore.

Try to work and sleep in a cool place. If your room is too hot, turn on the air-con or use a fan. Other things you can do to keep your body cool are:

• Avoid too much spicy food that may cause sweating

• Avoid drinking hot beverages

• Avoid expose yourself to heat, like taking a shower with hot water and standing under direct sunlight.

Taking antihistamine before exercise may help to prevent the urticaria.

4) UV Light

Although rare, UV light or sun exposure can cause hives (solar urticaria). Prevent this from happening by wearing a cap, sunglasses, and a long-sleeved shirt to cover your skin outside.

5) Vibration

This is another rare trigger. Vibration from machinery like electric mixers can cause hives. If you work in a food and beverage (F&B) industry job, you might need to use these kinds of machines at work daily. Ask your employer if you can take a break or change to a manual tool instead.

See your GP at your nearest polyclinic if you keep having skin irritation and itching because of work machinery.

Type 2: Chronic spontaneous urticaria (CSU)

Let’s move on to the next type of chronic urticaria – chronic spontaneous urticaria or CSU.

CSU has no known cause.

Since doctors can’t always find the cause, it can be hard to treat spontaneous urticaria. Patients can get frustrated. If you are one of them, know that you are not alone.

Spontaneous urticaria may have a link with thyroid (a small gland at the front of your neck) disorders, so your doctor may perform a thyroid function test. Your doctor may also check if rare inflammatory diseases that cause hives in adults and urticarial vasculitis are associated with your CSU. No need to worry about these for now, as your doctor will provide more specific advice if you have these other conditions.

For those cases of CSU that have a known trigger, the trigger is usually NSAIDS painkillers or alcohol. It’s not usually triggered by food.

You can take the UCT (Urticaria Control Test), a tool to check how bad your hives are. (Click the link to see what are the test questions.)

How to prevent urticaria: 2 triggers to avoid

1) Avoid NSAIDs painkillers

Don’t take NSAIDS painkillers like aspirin and ibuprofen. If you need pain relief at home, choose non-NSAIDS painkillers like paracetamol (Panadol) and Tylenol instead.

2) Advice on food and alcohol

Some foods are high in histamines.  These include fermented foods and alcohol.  Avoid such foods will help to control the urticaria.

You’ve learned how to prevent hives in this article. But if you already have hives and want to know how to manage them, check out our guide for hives treatment at home.

What is angioedema?

Angioedema is a medical condition causing deeper tissue swelling under the skin. It can happen together with hives. Angioedema affects the eyes, lips, and skin, and it usually lasts longer than hives.

While having angioedema may make one feel embarrassed and uncomfortable, it can also be life-threatening.

What causes angioedema?

Some patients have hereditary angioedema. Some may have allergic angioedema due to ingestion of food or medication or contact (items made of natural rubber). Non-allergic angioedema may occur after some weeks or months of usage of angiotensin-converting enzyme ACE inhibitors ( a type of  blood pressure medication). Some may have idiopathic angioedema where no known cause can be found.

How to prevent angioedema: 2 triggers to avoid

1) ACE inhibitors

ACE inhibitors are usually found in high blood pressure medication. They can cause angioedema as a side effect. If you develop angioedema after taking high blood pressure medication with ACE inhibitors, tell your doctor so they can suggest alternatives.

2) Food

If you have angioedema due to food such as shellfish, peanuts, tree nuts, eggs, and milk, you should stop consuming them.

Complications from hives (urticaria) and angioedema

If hives and angioedema spread throughout the body, they can cause problems like hypotension and anaphylaxis.

1. Hypotension

When your blood pressure is a lot lower than normal. This is risky because it means your vital organs - brain, heart, liver, etc., aren’t getting enough blood and could lead to organ failure.

2. Anaphylaxis

A serious allergic reaction that can cause breathing problems. Someone with anaphylaxis could go into shock and collapse within minutes.

Hives and angioedema can happen when you are exposed to certain triggers. Avoiding these triggers may not completely prevent hives, but it can lower the chances of getting hives. However, sometimes, there is no clear cause.

Ref: H24

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