Urticaria and Angioedema
What are hives?
Hives (also known as urticaria) look like mosquito bites.
They range from the size of a pinhead to that of a dinner plate.
Although some unlucky individuals can have them every day for
weeks, individual lumps usually go in minutes to hours. In most
people, hives are not due to allergy.
How common are hives?
Approximately 1 in 6 people will develop hives some time during
their life and are most common in children. They eventually disappear
in most people. They may reappear following infection, when under
stress or for no particular reason.
Hives occur in the skin
Underneath the lining of the skin, gut, lungs, nose and eyes
are mast cells. These are designed to kill worms and parasites.
Mast cells are like "land-mines", and contain "bags"
filled with irritant chemicals including histamine. When these
are released in small amounts, they cause local itch and irritation.
In larger amounts, they will cause fluid to leak out of blood
vessels, resulting in swelling of the skin. Occasionally, hives
may not be itchy at all.
Can
hives occur anywhere else?
Swelling of the lips and face is uncomfortable and cosmetically
embarrassing, but is not dangerous. Around 1 in 3 people with
hives can also have swelling of the tongue and throat. This is
called angioedema, and is caused by similar swelling deeper in
the tissues. Occasionally the swellings will occur inside the
stomach and cause tummy pain or cramps.
Can hives be dangerous?
Hives on the outside don't harm us. They are not damaging
inside organs like kidneys, liver or lungs. The only danger is
if the tongue swells or the back of the throat swells severely.
Since this can cause difficulty breathing, this is a symptom that
needs to be taken seriously. Urgent medical treatment is required
if this occurs.
Are hives always itchy ?
Usually, but not always ! Occasionally, swelling in the deeper
layers of skin (known as "angioedema") can even be painful
or burning, particularly when it occurs over joints. These sometimes
last for days.
Hives are rarely caused by terrible disease
Hives are rarely due to a nasty underlying disease. Common
causes include infection (particularly in young children), or
contact with animals or plants. Allergic reactions to food, pain
killers (such as aspirin or arthritis tablets like naproxen, diclofenac)
or antibiotics can also trigger hives. Sometimes insect stings,
food additives or preservatives can trigger hives. Stress can
certainly make established symptoms worse, but is a very rare
cause of urticaria.
Most people with urticaria do not need tests
Tests are sometimes done when hives go on for long periods
or when unusual symptoms are occurring around the same time. This
is to exclude other diseases, which may appear as hives first
and other conditions later. Allergy testing is performed when
the history suggests of an allergic cause. Allergy testing is
rarely required when episodes of hives are prolonged.
There are circumstances when tests are required to rule out underlying disease or help exclude conditions that can look like hives. Examples include some cases of prolonged hives, when the person is unwell/sick (as hives may make you itchy and tired, but rarely "unwell"), or when there are unusual features like lumps lasting for days at a time or bruising. Under these circumstances, blood tests and sometimes a skin biopsy (tissue sample) may be performed to exclude conditions like urticarial vasculitis (see figure below).
Urticarial
vasculitis
"Ordinary" hives don't make you sick
Hives may make people tired due to lack of sleep, but not "sick".
They are not affecting you internally or interfering with essential
organs like liver or kidneys. The only danger of "routine"
hives is if the tongue or throat swell and cause difficulty breathing,
a condition known as angioedema (see below).
Types of Hives
It may surprise you to learn that there are many different
types of hives. Whilst most people have their lumps and bumps
come up spontaneously without any clear triggers, others find
that things that they eat, drink or do can make them appear more
often. For example, there is a group of conditions known as the
"physical urticarias". These hives come out with various
physical stimuli to the skin. Symptoms occur alone or accompany
spontaneous hives. While there is rarely an important underlying
disease, exceptions occur. For example, solar urticaria has been
associated with a rare condition called hypereosinophilia syndrome,
and occasionally SLE/lupus.
Examples of the "physical urticarias" inlude:
Cold:
Cold air, immersion in cold water, cooling of the skin while sweating
(uncommon). The major significance of this condition is the risk
of severe allergic reaction with whole body cooling such as when
swimming in cold water. There is a small risk of drowning if severe
dizziness or blackouts occur when swimming alone.
Heat: Contact with hot objects
or food (rare)
Aquagenic: Hives occur upon
contact with water (rare)
Solar: Hives occur upon exposure
to sunlight (rare)
Vibration: e.g. using lawnmower
or power tools (rare)
Delayed Pressure: Occurs several
hours after leaning on elbow or carrying heavy bags or sitting
on a hard seat (uncommon)
Dermographism: Hives occur
when the skin is rubbed or scratched, or when irritated by tight
clothing (very common, around 1/600 people)
Cholinergic: Red blotchy areas
with or without small pimple-sized lumps occur when people sweat
e.g. exercise, stress, saunas, after alcohol, spicy food (very
common, perhaps up to 5% of adolescents transiently)
Cholinergic urticaria (left); Dermographism (centre and right).
Cold urticaria (left and centre); Heat urticaria (right).
Angioedema can occur on its own
Angioedema occurs in around 1 in 3 people with hives. It is
caused by similar swelling deeper in the tissues. Angioedema is
not always itchy and can sometimes be painful. Sometimes it can
occur on its own. As well as in infection and allergy, angioedema
is also seen in two other situations. Around 1 in 100 people taking
heart/blood pressure medicines called ACE (Angiotensin Converting
Enzyme) inhibitors will develop angioedema.
The tendency to angioedema can be inherited
Hereditary angioedema (HAE) occurs in around 1 in 100,000
people. Patients lack an effective enzyme (known as C1 esterase),
which is associated with non-itchy swellings of the face, throat
or limbs. Swelling of the gut is a common symptom, resulting at
times in severe abdominal pain and sometimkes uneccesary surgery.
Examples of angioedema of the face
How long do hives last?
Most hives go away within days to a few weeks. Occasional
unlucky individuals will have itches and swellings that come and
go over many years. Fortunately, that is the exception rather
than the rule!
Treatment of urticaria and angioedema
References
