Urticaria

What is Urticaria (Hives)?

Urticaria, also commonly known as hives, is an itchy rash caused by tiny amount of fluid that leaks from blood vessels just under the skin surface. The rash may be triggered by an allergy, or by another factor such as heat or exercise. In most cases, the rash lasts 24-48 hours and is not serious.

Urticaria is classified as:


1. Acute urticaria
      • It develops suddenly and last less than 6 weeks. Most cases last about 24 to 48 hours. It can affect anyone at any age. Some people have recurring bouts of acute urticarial.

2. Chronic urticaria
    • It persists longer, more than 6 weeks. This is not uncommon.


What happens to the skin in urticaria?

The redness and swelling are due to changes in the small blood vessels of the skin. This leads to increased blood flow to the affected skin, and excessive fluid moves into the surrounding tissues. Histamine is the predominant chemical mediator for these changes and it causes the sensation of itch. Histamine is released by the mast cell, a special type of immune cell in the skin. Mast cells release histamine when stimulated by mast cell stimulators or activators.


What is the appearance of urticaria?

The rash usually appears suddenly and can affect any area of the skin. Small raised areas known as 'wheals' develop on the skin. These wheals appear like "mosquito bite reaction and they are extremely itchy. Each wheal is white or red and is usually surrounded by a small red area of skin called a flare.

These wheals vary in size and they make the affected area of the skin appear blotchy and red.

The rash can also appear quite dramatic if many areas of skin are suddenly affected.


What causes urticaria?

The cause of acute urticaria is frequently not found. Known triggers include:

  • Allergies

    1. Food such as nuts, strawberries, citrus fruits, egg, food additives, shellfish.
      It can occur even if you have eaten it many times before without any problem.

    2. Insect bites and stings.

    3. Medications like penicillin, aspirin, and pain killers.

  • Viral infections such as cold or 'flu' can trigger an urticarial rash in some people.
    A mild viral infection, which causes few other symptoms, probably triggers an urticarial rash that develops without an apparent cause.

  • Skin contact with 'sensitisers' can cause urticaria in some people, e.g. latex, plants, etc.

Like acute urticaria, there is usually no readily identifiable cause for chronic urticaria. It has been found that some cases of chronic urticaria may be autoimmune in nature. These patients have immune cells targeting the mast cells leading to the release of histamine.


Signs and symptoms

The most common locations for hives include:

  • Trunk

  • Limbs like arms, forearms, thighs and legs though it can affect many other areas

  • Swelling of the eyes, lips, hands, feet or genitals can sometimes occur.

    This swelling is called angioedema and it usually goes away within 24 to 48 hours.
    People who have severe allergic reaction to peanuts, insect stings, etc often have an urticarial rash as one of the symptoms. This is in addition to other symptoms such as severe angioedema breathing difficulties, etc.
    This means that the rash keeps coming and going on most days for 6 weeks or longer. This is not uncommon.


Is urticaria serious?

This is usually not serious. The rash is itchy but normally fades within a day or so and causes no harm. Most people with acute urticaria do not feel unwell unless they have a cold or 'flu' that is triggering the rash. The cause of the rash is not known in more than half of the cases and it is commonly a 'one-off' event.


However, complicated cases may arise in the following situations:

  • Food allergy

If a food allergy is the cause then the rash is likely to return each time you eat the particular food. This is more often a 'nuisance' than serious.

  • Severe allergy

    People who have severe allergic reaction to peanuts, insect stings, etc often have an urticarial rash as one of the symptoms. This is in addition to other symptoms such as severe angioedema breathing difficulties, etc.

  • Chronic urticaria

    This means that the rash keeps coming and going on most days for 6 weeks or longer. This is not uncommon. 


If you are experiencing mild hives, you can help reduce the discomfort by:

  • Taking cool showers

  • Applying cool compress

  • Wearing loose-fitting clothes

  • Avoiding strenuous activity

  • Taking an antihistamine

Meanwhile, try to find out what is triggering your hives and avoid whatever the trigger is.


When to seek medical attention?

Before visiting your doctor, try to notice what might be triggering your hives and whether it worsens with exposure to heat, cold, pressure, vibration, etc. Try to recall any recent illnesses you may have had since some illnesses can trigger hives.


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