Urticaria

Also known as hives

Urticaria (also known as hives) is an itchy rash that can appear like welts, anywhere on the body. These welts come and go in a random manner and it can last from hours or days (acute) to months (chronic). Angioedema is similar to hives, but the swelling occurs beneath the skin instead of on the surface.

Key points

  1. Urticaria is common with one out of five people getting it at some stage in their life.
  2. 80% of cases of hives occurring in adults are not due to allergy.
  3. Non-allergic hives can come and go any time of the day, and often occurs overnight or first thing in the morning too. 
  4. A cause or trigger can only be identified about 50% of the time. 
  5. Treatment tends to include use of non-sedating antihistamines to reduce the histamine response which causes the skin reaction. 

What causes urticaria & angioedema?

image of itchy rashHives and angioedema form when blood plasma leaks out of small blood vessels in the skin in response to histamine release. Histamine release can be triggered by a wide range of factors such as:

  • allergens
  • foods (fresh foods cause hives more often than cooked foods)
  • food additives and preservatives
  • latex rubber (this can be gloves, elastic in clothing etc)
  • environmental factors (cold, heat, vibration etc)
  • medicines (eg. aspirin, non-steroidal anti-inflammatory drugs, codeine to name a few)
  • our genes (eg. hereditary angioedema is passed on through families) 

While working out what has caused urticaria or angiodema is helpful, a trigger is only identified in about half of cases. 

Types of urticaria

There are three main types of urticaria. 

  • Acute urticaria – hives or swelling lasting less than 6 weeks duration, and most cases only last hours to two days.
  • Chronic urticaria – lasts 6 weeks or more, with daily or episodic weals.
  • Physical urticaria – also known as inducible urticaria, caused by direct physical stimulation of the skin.

Symptoms

The key symptoms of urticaria are:

  • itchy rash
  • red or white whelts/patches or wheals of varying size (commonly 1 to 2 cm across) 
  • welts are often surrounded by a red flare and may change shape
  • whelts come and go lasting few hours to one day, sometimes longer
  • new whelts may keep appearing with the rash appearing to move around the body

The symptoms of angioedema are: 
  • deeper swelling of eyelids, lips, hands and elsewhere
  • rarely this can lead to narrowing of the airway and breathing problems
  • angioedema may occur with or without urticarial wheals (10%).

Warning: Seek medical help right now by ringing 111 in NZ if any: 

  • urticarial rash within 20 minutes of eating or taking a new medicine, OR
  • rapid swelling of the lips, mouth or airway making it hard to breathe

Diagnosis of hives & angioedema

The key to finding out the cause of hives or angioedema is a careful history and examination of your skin for any rash or whelts and your face/body for any swelling. The types of questions they may ask include:

  • When and where did the rash begin?
  • What did you have to eat just before it began?
  • What is your usual diet?
  • Are you taking any medications or started anything new just before your symptoms began?
  • Do you live or work in an environment where you come into contact with possible triggers, such as pets, chemicals or latex gloves?
  • Have you been stung or bitten by an insect just before your symptoms started?
  • What has your health been like? Any recent infections?
  • Have you recently travelled to a foreign country and if so, where?
  • Does anyone in your family have urticaria or a similar rash? (1) 

Tests 

  • Skin tests and blood tests may be performed if the symptoms are ongoing or more severe. 
  • Patch testing is a useful way to identify contact causes such as rubber, cosmetics, plants or ointments. 

Is acute urticaria serious?

While the rash of urticaria can be very itchy and annoying, it usually settles within a day and causes no harm. However, there are times when urticaria may be more serious and indicate a serious allergic reaction, drug reaction or even life threatening anaphylaxis

Treatment of urticaria (hives)

1. 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. 

2. Antihistamines. Since the skin reaction is caused by histamine release, most people benefit from taking one or two days of non-sedating antihistamines such as loratadine or cetirizine for acute urticaria. These medicines block the action of histamine and can be brought from a pharmacy or prescribed by a doctor or nurse practitioner. 

3. Avoid the causes/triggers. If the cause is a specific food, cosmetic, food additive, shellfish or other, then avoiding these foods or substances can reduce the risk of urticaria or angioedema recurring.(2)

4. Topical lotions. You can also apply calamine lotion or menthol 1% in aqueous cream to reduce the itching. 

5. Severe cases. If the rash is widespread or you have any swelling of your mouth or airways, seek medical help right now. You may need steroid tablets and admitting to hospital to identify the cause and prevent life threatening reactions. 

Physical urticaria

Physical triggers may include cold, heat, exercise, sunlight, vibration, pressure and, rarely, water. Dermatographism or "skin writing" is easily recognised by the appearance of weals or welts on the skin as a result of being stroked, scratched, rubbed, and sometimes even slapped. 

  • This is one of the most common types of urticaria and is seen in 4–5% of the population.
  • The hives usually appear where the skin was stimulated or exposed and not anywhere else. 
  • The timing is helpful as most hives due to physical urticaria appear within an hour after exposure.

Learn more

Acute urticaria DermNet NZ
Images of urticaria & angioedema DermNet NZ
Allergies & hives (Urticaria & angioedema) WebMD

References 

  1. Diagnosing urticaria NHS Choices, UK
  2. Alexandroff, A.B. and Harman, K.E. (2010), Urticaria: an evidence-based update. Conference report [abstract]. British Journal of Dermatology, 163: 275–278. doi: 10.1111/j.1365-2133.2010.09884.x
Credits: Editorial team.