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Commonly
called hives, or nettle rash, urticaria is an
itchy kind of skin rash. There is always itchiness,
and sometimes there are associated swellings of the
skin called angioedema.
Urticaria consists of anything from one to countless
weals, and these may be anything from a half centimetre to many centimetres
in diameter. A weal is an itchy and raised area of skin that is reddened
around the edge, but often paler in the middle. Unlike eczema,
urticaria is not scaly, and sufferers do not shed flakes of skin.
Urticaria is what happens when cells near to the surface of the skin
are stimulated to release histamine. This substance is involved in the body's
normal defence mechanism, and it is the main substance to cause
the symptoms we associate with allergy. If released in the nose,
histamine causes the symptoms of
hay fever, if released in the lung, histamine causes the symptoms of asthma and if released in the
skin, histamine causes urticaria. The hairs on the surface of a nettle leaf contain histamine,
and this is why urticaria is similar to nettle rash.
In some cases, itching
happens without rash, and
this condition is called pruritis. The
weals of urticaria whiten if pressure is applied to the rash.
The rash generally disappears within a few hours, although in some cases, crops of
wheals continue to appear for days or even months.
Urticaria
is described by the length of time that
symptoms last. If there is just a single attack and it lasts less than six weeks it is called
acute urticaria.
When episodes last more than six weeks the condition is described as chronic
urticaria. When it has been shown that pressure, scratching, cold, heat,
exercise or sunlight exposure triggers an attack the condition is called
physical
urticaria. When it has been shown that an allergy triggers an attack, the condition is called
allergic
urticaria. When no external or internal cause for the
urticaria can be found, the condition is called idiopathic
urticaria.
Most cases of
urticaria tend to disappear in due course. For
example, around a half of all cases that have lasted six
weeks will have gone by a year. Only in a small
percentage of cases will urticaria continue for
several years. It is the cases that are more severe
and more persistent at the time of onset that tend
to last longest. For example, amongst cases severe
enough to be referred to
hospital for an opinion, one case in five will
persist for more than ten years. However, this also
means that in four out of five cases referred to
hospital the condition will eventually clear up.
Urticaria is very
common; approximately one person in five will
experience it at some time in their life.
Physical urticaria
Urticaria (hives) can be set off by
physical factors. Most cases of urticaria are made worse by
warmth, but in some people particular forms of physical stress to the skin
can induce it. These are scratching (dermographism), cold, sustained
pressure,
sunshine (the sunlight not the heat) or water (not the heat or coldness). The last two of these are rare causes of urticaria.
There is a tendency to dismiss these cases
of physical urticaria and
conclude that allergy is not the cause. However, cases have been described where
the avoidance of a food (e.g. a regularly consumed
food such as wheat or milk) has cured the problem - i.e.
the physical stimulus then no longer triggers the symptoms.
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Dermographism
- about 1 case in 10
Linear wheals occur a few minutes after
the skin is scratched along the line of the
scratch. These weals resemble the hives
of urticaria, and it happens when this
particular stimulus induces the release of chemical mediators from
cells in the skin.
In certain cases it is possible for the
dermographism tendency only to occur when the
individual is exposed to an 'allergen' such as a drug or a
food, but to disappear when the effects of
that exposure have worn off. |
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Dermographometer
 
The marks on the right are produced
when blunt probes that depress the skin to various
depths are
applied in a linear fashion with
this simple instrument.
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Cholinergic
urticaria - about 1 case in 20
Cholinergic urticaria is urticaria that
usually starts as tiny wheals surrounded by
redness that occurs with with conditions
normally associated with sweating.
Exercise, hot showers, emotion and anxiety can
all cause the condition. The rash first
appears as a flushed appearance on the neck
and upper chest usually accompanied by intense
itching. The rash can then spread to
form a rash of small urticarial wheals
involving the face, back, and extremities.
Watering eyes, increased saliva production and
diarrhoea can occur at the same time.
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Cold
urticaria - about 1 case in 30
Cold urticaria is the rapid onset of itching, redness, and swelling
of the skin after exposure to something cold. To test for this, an ice-cube can be placed on the forearm for
10-15 minutes. A positive reaction leads to a hive in the shape of the ice cube within 10 minutes
after the source of cold has been removed. A similar condition is cold-dependent
dermographism where hives form if the skin is both scratched and
chilled. |
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 Ice
cube test for cold urticaria
An urticarial weal appears after a few
minutes on skin re-warming at the
site where an ice-cube is
applied to the forearm for 15 minutes.
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Delayed
pressure urticaria - about 1 case in 50)
This usually occurs a few hours after pressure
has been applied to the skin. There may
be either a rash or swelling, or both,
occurring around tight clothing, the hands may
swell with activity involving gripping such as
using a spanner, foot swelling might occur
after walking or buttock itching and swelling
may occur after sitting for a few hours. Cases
have been described where this only happens
after the patient has eaten a particular food
- i.e. food allergy causing delayed pressure
to cause urticaria. In such a cases the skin
prick test may show a delayed, but not
immediate, response to the food.R |
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Solar
urticaria - rare
Solar urticaria is a rare disorder in which brief exposure to bright light causes the development of hives within
a few minutes. Typically intense itching will occur 30
seconds after exposure to sunlight, and this is followed by swelling with rash or redness of
the light-exposed skin. This usually takes several hours to settle.
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Aquagenic
urticaria - rare
This is a rare disorder in which sufferers develop small itchy
wheals after contact with water, regardless of its temperature.
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Allergic urticaria
Brief attacks of urticaria may sometimes
occur when an individual with a food or insect venom allergy becomes
exposed to the responsible allergen. When the allergen (for example,
the responsible protein in the food or insect venom) enters the body, it
causes the release of histamine and other immune mediators into the blood and
this can result in hives
and/or other allergic symptoms. However, in such cases the patient is
usually aware of the food or insect allergy and the
cause of the rash is clear.
Patients suffering
from chronic urticaria are very often referred to
allergy clinics in the belief that they suffer from
food allergy - 'to find out what they are allergic
to'. In a considerable majority, food allergy is not
the cause and this can easily be established by
taking a careful medical history. When attacks of
urticaria only happen from time to time, stress or
response to an innocent infection are more likely
explanations.
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Food
allergy
True food allergy
causes about 1 case of chronic urticaria in
50. When true food allergy is the
explanation for urticaria, the attacks are likely to
start quite soon after the food has been eaten
(almost always within an hour), and the association is usually
obvious to the sufferer.
Foods likely to cause this problem include egg, milk, fish, shellfish, nuts and
seeds and skin prick tests will confirm this.
Taking
exercise shortly after eating wheat is an
occasional cause of urticaria. Taking exercise
shortly after eating other foods such as
celery or shellfish might provoke delayed
urticaria or even anaphylaxis. Foods and food additives may
also provoke urticaria by mechanisms other
than true allergy and these are less easy to
diagnose. When food additives
('e'-numbers) are found to provoke urticaria,
this is not due to true allergy, and so
allergy tests are unhelpful. The association
has to be shown by undertaking an elimination
diet. In the case of very
persistent urticaria where no cause can be found and skin testing is
unhelpful, an elimination diet may also be
helpful to see if an intolerance of a natural
food such as wheat or milk might be the
explanation. It is best if such diets are
undertaken with professional help.
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Rubber
latex allergy
Rubber latex
is derived from the sap of the rubber tree. It is the basic ingredient of rubber and
as such is present in surgical gloves and many other kinds of medical equipment. It
is also commonly encountered as balloons,
contraceptive devices (condoms and diaphragms) and rubber bands.
In the person with a true rubber latex
allergy, exposure to it can
cause swelling or rash (angioedema or urticaria) both at the site of contact (e.g. the
hands or lips) and at distant sites such as the throat.
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Insect
stings
Insects
stings (e.g. bee, wasp, yellow hornet,
mosquito or fire ant) can cause allergic reactions and
urticaria is usually a prominent feature. The
large local swelling that occurs at the site
of an insect sting is not
evidence of allergy as it occurs to some
degree in everyone who is stung. It is due to
a chemical reaction to a toxin in the venom.
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Drug-induced
urticaria
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True
drug allergy
When a drug causes urticaria, true drug
allergy (= due to an immune reaction) will
occasionally be the explanation. The number of
different drugs that can cause allergic
urticaria is very wide, the commonest being
antibiotics and particularly those in the
penicillin group. Opiates and
codeine-containing medications can also cause
the problem.
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Aspirin
and NSAIDs
Aspirin,
along with the closely related painkillers called non-steroidal
anti-inflammatory drugs (NSAIDs), can occasionally cause urticaria, angioedema and
even anaphylaxis. However these are 'allergy-like' reactions, an
immune system mechanism is not involved, and so the
diagnosis cannot be made by allergy skin test or blood test. When a single
dose or short course of one of these drugs has
been taken just before a brief attack, or just
before the start of a longer attack, the
possibility of a relationship may not be
difficult to spot. But the possibility of
a relationship may be difficult to spot in someone
who has been on regular treatment with one of these drugs
for some time when the urticaria first begins. In such
cases, the temporary cessation of the drug, or the temporary
substitution of the suspected drug by another may be the only way to establish
the relationship.
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ACE
inhibitors
A particular group of heart pills called ACE-inhibitors (the chemical names
end in -pril, e.g. enalapril, lisinopril, ramipril) can occasionally cause
urticaria, although they more commonly cause angioedema; about one
person in 100 who takes an ACE inhibitor is
likely to get this problem.
The reaction is not caused by true allergy, allergy skin and blood
tests do not show it, so why does it happen? Reactions are thought to occur because
an unwanted pharmacological effect of the drug causes the release of
compounds similar to those released in an allergic reaction.
The only way of showing that a regular medication is the true cause is by
stopping or changing the treatment.
To
complicate matters, the angioedema attacks may
not start until the individual has been taking
the ACE inhibitor for months or even years
making it difficult to spot the relationship.
Also, attacks may continue for several weeks
after the drug has been stopped.
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Beta
blockers
Other drugs such as beta-blockers (the chemical names
end in -olol, e.g. drugs such as metoprolol) that are used for high blood
pressure, heart rhythm problems and anxiety can cause angioedema in a
similar way. Beta-blockers have the additional
disadvantage that they cause patients taking them
be
resistant to the beneficial action of the adrenaline
injection treatment that is used to counteract
severe allergic emergencies such as
anaphylaxis or laryngeal oedema.
Patients who are considered
sufficiently at risk from an allergic
emergency to be prescribed an adrenaline
injection (e.g. Epipen) for emergency use
ideally should not be taking a beta-blocker.
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Food
additives and natural salicylates
Although they are not drugs,
compounds similar to aspirin are
present in many foods and food additives (e.g. certain food dyes and preservatives and
naturally occurring salicylates
in certain fruits and vegetables) and they may act in a similar way as
aspirin to provoke angioedema and urticaria.
So some people, especially those with a
history of allergy to
aspirin
or NSAIDs, may need to avoid these
foods and food additives to relieve the urticaria.
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Urticarial
vasculitis
In the vast majority of cases
urticaria, although a nuisance, is a harmless
condition and no special tests or investigations are
needed. However, in the occasional case there may be
an unusual feature to the condition, or other
symptoms may be present that suggest that the
urticaria may be due to an underlying condition.
Blood vessel inflammation or 'vasculitis' will then
be involved.
The
following features would indicate to a doctor that
further tests to exclude an underlying cause are
advisable.
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Individual
weals last more than 24 hours
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Weals tend to bruise, or to leave bruises behind
them
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Weals are tender on pressure
and the rash may be painful
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There
is an unwell feeling at the time of attacks
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Other symptoms
occur such as joint pains, bruising and stomach pains
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In this
case a
specialist will advise special blood tests
and a skin biopsy. This test involves examining a
sample of skin from one of the wheals to see if urticarial
vasculitis, an inflammation of blood
vessels, is the cause.
Idiopathic urticaria
Ĭdiŏpăth´ic
adj.
Describes
a condition that arises
spontaneously and without known cause Although
the term idiopathic describes a disease or condition
that is without known cause, allergy specialists
prefer not to make the diagnosis of idiopathic
urticaria without at least
considering allergy or hypersensitivity. Many explanations have been put forward, and
amongst these are several that may be worth considering, particularly if
the condition is severe, and antihistamines are unhelpful. Recent research has suggested that
up to a
half of patients with idiopathic urticaria have the condition
because an auto-antibody is present – i.e. the
immune system has formed a self-directed antibody - autoimmune
urticaria. The test for the
condition, the autologous serum skin test, is at
present done only for research purposes. But because
the treatment of the condition is no different if the
auto-antibody is present and as it is unlikely that
the presence of the auto-antibody rules out the
possibility of there being external triggers, the test
does not alter menegement.
It is described below for interest only. Autologous
serum skin test
In this test, normally
only used for research purposes, a sample of
the patient's blood is taken and centrifuged to
remove the cells. The resulting liquid is called
blood serum, and a small quantity is injected just
under the skin of the patient's arm.  If the test is positive, an urticarial weal will
occur after a few minutes at the site of the
injection indicating that histamine is being
released in response to a factor in the patient's
own serum.
In such cases,
blood test markers of other autoimmune conditions
may be found to be present. Autoimmune
thyroid disease
One of these is the
anti-thyroid antibody test, the marker for autoimmune thyroiditis. This auto-antibody is
found in most cases of under active thyroid - the
condition called hypothyroidism. If found, and if the
patient is also found to be hypothyroid, thyroid hormone
treatment is likely to relieve the urticaria. More
intriguingly, some specialists have found that urticaria
appears to be improved by treatment
with a small dose of thyroxine in patients who have
the anti-thyroid antibodies even when thyroid blood
tests simply in the low normal range.
Many other possible explanations for idiopathic
angioedema have been put forward, and some of the more plausible are
given below:
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Food
intolerance
A food or food
additive intolerance is sometimes suspected to
be the cause of chronic urticaria. Whilst true
food allergy can be diagnosed by skin prick or
blood tests, food or food additive intolerance
cannot be diagnosed in this way. A supervised elimination diet
trial is the only available method and this is
normally reserved for more severe and
persistent cases of urticaria when simpler
measures have failed.
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Yeast
hypersensitivity
In the same way that allergy tests may fail to pick up sensitivity to foods or food
additives as a cause of urticaria it has been suggested that sensitivity to
gut yeasts such as Candida and the food yeast Saccharomyces
may be a common cause and yet fail to show up on standard
allergy tests.
40 years ago, two groups of UK researchers put
this theory to the test. They used the combination of a low sugar
and yeast diet and
the antifungal drug Nystatin as the treatment.
They reported
that two thirds of chronic urticaria sufferers were improved as a result of
this treatment. Unfortunately these
studies were not blinded (the patients knew what treatment they were
having) and have never been repeated. A further blinded study (neither the patient nor the
doctor know whether real or dummy treatment is being taken) is
therefore needed to
confirm the theory before this approach can be generally
recommended.
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Athlete's
foot fungus infection
Another interesting observation was first made in 1930! A female patient suffered from
urticaria, severe asthma and athletes foot infection. When skin tested with an extract of
athletes foot fungus, not only was the skin test positive, the
patient developed itching, urticaria, violent sneezing and
wheeze. When the athletes foot
infection was treated by a course of antifungal tablets, not only did the foot
condition clear up, the urticaria and the asthma cleared up as well. Recent studies suggest that this observation
may well be genuine, and
suggest that sensitivity to moulds yeast and fungi are probably being overlooked as a
cause of chronic allergy problems such as urticaria.
As it is not
clear whether fungal allergy or just fungal
infection on its own is linked to chronic
urticaria it makes sense to treat chronic
fungal skin infection in patients who suffer
from chronic urticaria as it is always
possible that treating the infection may up
the urticaria even without evidence of fungal
allergy.
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Airborne
allergy
A third possible explanation for otherwise unexplained urticaria
and/or angioedema concerns allergy to airborne allergens such as house
dust mites or mould spores. Occasional patients who suffer from
urticaria and/or angioedema will have positive skin tests to one of
these allergens, and it is then almost impossible to say whether this
represents cause and effect, or whether it is simply
coincidence.
Other
patients with negative allergy tests report
that symptoms improve or disappear when they
go somewhere with a dry climate, and re-appear
when they return. In addition, some patients
report that changes in the weather affect
their symptoms in a similar way, worsening in
damp weather and improving in dry weather,
particularly when out-of-doors. The fact that
allergy skin prick and blood tests appear to
under-diagnose mould spore allergy (intradermal
skin tests may pick up missed
cases) may be the explanation.
The possibility that airborne allergy (house dust mites, mould spores)
provokes urticaria and angioedema has never been systematically
studied. Until it is, patients who suspect their condition is being
provoked in this way should consider taking avoidance
measures to reduce their exposure.
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Nickel
allergy
Contact eczema caused by contact with the metal nickel (nickel
dermatitis) is a common and well-known disorder. The
possibility that people who suffer from nickel dermatitis might also suffer chronic
urticaria caused by nickel salts present naturally in foods remains a matter of some debate.
A recent study
from France,
investigated 21 chronic urticaria patients. The
patients were selected because they happened also
to suffer from
nickel dermatitis. 15 out of the 21 patients developed symptoms after an oral
challenge with a nickel salt. A low nickel diet was effective in 11 out of the 15, and
it was possible to stop drug treatment in nine. In addition, four patients who had
nickel-containing dental materials in their mouths had these materials removed and also
followed a
nickel-avoidance diet. In two out of the four cases the chronic urticaria
disappeared. This would suggest that a diagnosis of nickel-induced food allergy
should be considered in patients with unexplained chronic urticaria, especially if they
are known to suffer from nickel dermatitis. Further studies are need to confirm
this interesting observation.
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Helicobacter
stomach infection
Infections
may play a contributory role in a few cases, of
chronic urticaria and when present, chronic
infections such as dental sepsis, sinusitis,
urinary tract infections and cutaneous fungal
infections should be treated.
Infection
with the peptic ulcer-associated stomach
bacterium Helicobacter pylori has been
proposed as a possible cause of chronic
urticaria. Testing for the presence of this
organism used to be difficult, but now it can
be done quite simply from a small sample of
faeces. Several studies have no used
antibiotic treatment against Helicobacter
in an attempt to clear up chronic urticaria.
The results of these studies have now been
combined into one study and they provide
reasonably strong evidence that urticaria may
clear up in about a third of cases treated in
this way.
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Managing
urticaria
Simple measures
can reduce the frequency and severity of symptoms. They also give sufferers a sense of control over their
condition.
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Avoid
physical triggers
Keep cool, avoid getting hot
from exercise and find the best temperature for a bath or shower. Resist the temptation to
scratch, and apply moisturising cream to areas of itch especially if dry. |
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Avoid
dietary triggers
Any of the following may set off a worsening
of symptoms in any patient. This is due to
intolerance rather than allergy.
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Alcoholic drinks
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Foods additives
- preservatives and artificial colourings
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Natural salicylates
- in certain spices, fruits, fruit juices
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Foods rich in amines - e.g.
strawberries, wines
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Avoid
provoking medicines
Avoid all aspirin or codeine containing
medication, avoid non-steroidals including ibuprofen (Nurofen®), diclofenac
(Voltarol®) and mefenamic acid
(Ponstan®). It is better to
use only paracetamol as a painkiller. People
with chronic urticaria who developed the
problem soon after starting taking aspirin
regularly as a precaution against stroke or
coronary heart disease should discuss a trial
of avoidance (or the temporary substitution of
another drug) with their doctor.
Carefully read the side effects list of any
other medication you are currently taking and avoid medicines that are
known to trigger urticaria or angioedema.
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Soothing
creams
Aqueous cream containing 1%
menthol is a useful soothing and anti-itch
treatment. Emollient (moisturising) creams and
lotions are very helpful to reduce itch and
the desire to scratch areas of dry or
excoriated skin.
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Treatment
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Antihistamines
In most cases, antihistamine treatment is a
highly effective way of controlling the itch
and rash of urticaria. Those patients for whom
urticaria occurs daily or most days will
usually do much better if they take a regular
long-acting one-a-day antihistamine such as
cetirizine (e.g. Zirtec®)
fexofenadine (Telfast®)
or loratadine (e.g. Clarityn®). In
some cases this will completely suppress the
rash and itching to such an extent that the
sufferer may not know if the condition is
still there! However, stopping the treatment
for a day or so will make the situation clear.
In some cases, regular
antihistamine treatment may have to be taken
for several weeks, and occasionally much
longer. Although it is best to do this under
the direction of a doctor, antihistamines are
not thought to cause any long-term problem
when taken for months or even years.
There is a tendency for
patients to under treat their urticaria,
especially when they do not take the advice of
a doctor. When urticaria occurs
daily or on most days, the best control is
achieved by taking a daily
long-acting antihistamine such as cetirizine, irrespective of
whether symptoms are present.
When urticaria happens
infrequently, it is best to take a
quick-acting antihistamine (e.g. acrivastine) promptly at
the first sign of an attack. Such
antihistamines are designed for their speed of
action, and if on-going relief is needed have
to be taken two or three times a day. |
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When
antihistamines fail
If a daily long-acting antihistamine is not
helpful, a doctor may prescribe a double (or
even higher) dose than the standard. This
should not be done without a doctor's advice
as only certain antihistamines are suitable.
Oddly, in some cases a stomach-ulcer treatment
may be added. This is not because of stomach
symptoms, acid suppressing drugs such as
cimetidine (Tagamet®)
and ranitidine (Zantac®)
are a different class of antihistamine and may
act synergistically to provide
better relief than using the standard
antihistamines alone. However, some experts
question whether these drugs really do help.
A new class of anti-allergy
treatment has recently been introduced. These drugs (e.g. montelukast
- Singulair®)
are called leukotriene receptor antagonists,
and trials have shown that occasional patients with
urticaria are helped more when these are added
than when they use antihistamines alone.
Short courses of oral
steroids (e.g. prednisolone) may sometimes be
prescribed for resistant urticaria. These can
be highly effective and are safe when used for
short periods. However, they are not suitable
for long-term use as troublesome side effects
may begin to be a problem after several weeks
or months of regular use.
Other
prescription drugs that may have an important
role in occasional cases (e.g. severe
angioedema and urticaria unresponsive to
simpler measures, hereditary angioedema)
include certain anabolic steroids and the
protease inhibitor tranexamic acid. |
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