| the Allergy Site Navigator
You are in > Medicine
For Home > Home
for related Products
The penicillin family
Penicillin belongs to a family of drugs called beta-lactam
antibiotics. Included in this family are the commonly prescribed
drugs ampicillin and amoxicillin. These medications are most
often used to treat skin, ear, sinus and upper respiratory
infections. They are relatively inexpensive and generally
effective at eradicating many common bacterial infections. They
aren't effective against viruses, however, so they aren't useful
against the common cold.
How penicillin allergy develops
No one is born allergic to penicillin, but you can develop an
allergy to the drug once you've been exposed to it. After that,
re-exposure to penicillin or related antibiotics can trigger an
Allergic reactions occur because your immune system responds to
the drug as if it were a harmful substance instead of a helpful
remedy. For reasons not fully understood, your body creates
antibodies called immunoglobulin to attack the medication. In
most cases of penicillin allergy, the type of immunoglobulin
that causes the most problems is type E (IgE). For the small
percentage of people who develop IgE antibodies, symptoms range
from annoying to life-threatening.
An anaphylactic reaction
The most severe type of reaction is what's called an
anaphylactic reaction, or anaphylaxis. The airway tubes
(bronchi) leading into your lungs may constrict, making it hard
to breathe. You might break out in hives, and your vocal cords,
lips or tongue may swell. Your blood pressure may drop to
life-threatening levels, making you feel dizzy or causing you to
An anaphylactic reaction usually occurs about 5 minutes to 2
hours after you take the penicillin. If you begin to have
symptoms of a severe reaction after taking any medication,
though, seek medical attention immediately.
Most other allergic reactions to penicillin occur after 2 to 3
days and aren't as severe or life-threatening. Often, the
allergy will show up as either hives or rashes, which can be
itchy or irritating. These rashes may be confined to one part of
your body, or they may spread to several areas. Sometimes the
reaction causes various parts of your body to swell, such as
your lips, face or hands. Delayed reactions sometimes occur
several weeks later.
Approaches to penicillin allergy
If you develop an allergy to penicillin, this doesn't mean
you're necessarily allergic to all antibiotics. Your doctor may
be able to give you an antibiotic that is distantly related to
penicillin without causing any problems. For example, among
people with positive skin tests for penicillin allergy, only a
small percentage are also allergic to a group of broad-spectrum
antibiotics called cephalosporin's. However, this risk is great
enough that people allergic to penicillin should be cautious
about taking those drugs.
If your doctor recommends that you avoid penicillin and
cephalosporin's, you can still take antibiotics totally unrelated
to penicillin to combat infections. However, these alternative
medications may be more expensive and less effective than those
related to penicillin.
If a penicillin allergy is suspected and you need to take
penicillin for an infection, the best way to confirm the
presence or absence of penicillin allergy is with a skin test.
This is done by injecting a tiny amount of the drug into your
skin and watching that part of your body for signs of
If the skin test for penicillin allergy is positive, you're at
an increased risk of a reaction if you take penicillin or
closely related antibiotics. If you have a history of
anaphylaxis within the first hour of taking penicillin and you
also have a positive skin test, you have at least a 50 percent
chance of having a reaction if you take penicillin again.
Even if you've had an allergic reaction to penicillin in the
past, it may be useful to have the test done again if you need
to take penicillin for an infection. With time, many people lose
their allergy to penicillin — if the suspected allergic response
was actually due to penicillin.
If you've ever had an allergy to penicillin, don't try the drug
again on your own to see if your allergy has disappeared. This
is very risky because a serious reaction could occur.
It's also important to know what it means if you have a negative
skin test for penicillin allergy. It doesn't mean that you're
free of penicillin allergy. It means that your risk of
penicillin allergy is roughly the same as that of the general
population — about 2 percent. Furthermore, people can develop a
new allergy to penicillin over time. Most of the time, your
doctor will be able to prescribe penicillin or a related
antibiotic if your skin test is negative.
There are times when doctors try to weaken and eventually
overcome a person's sensitivity to the penicillin allergen
(desensitization). They do this by administering small but
gradually increasing doses of penicillin orally or
intravenously. Because desensitization can trigger a
life-threatening reaction, however, it is only attempted in a
controlled hospital setting — and only when penicillin is
The bottom line
The main strategy for penicillin allergy is avoiding the drug
and its chemical relatives. Always report your allergies to
penicillin, or any drug, every time you visit medical
professionals. It also may be a good idea to wear a bracelet
that describes your allergy or carry a medical alert card in
your wallet or purse.
Symptoms of Anaphylaxis
- generalised flushing of the skin
- nettle rash (hives) anywhere on the body
- sense of impending doom
- swelling of throat and mouth
- difficulty in swallowing or speaking
- alterations in heart rate
- severe asthma
- abdominal pain, nausea and vomiting
- sudden feeling of weakness (drop in blood
- collapse and unconsciousness
Nobody would necessarily experience all of
Some people find that the allergy symptoms they
experience are always mild. For example, there may be a tingling
or itching in the mouth, or a localised rash - nothing more.
This is not serious in itself, and may be treated with oral
antihistamines. However, in some cases symptoms may become worse
over time. It is wise in all cases to make an appointment with
the doctor and seek a referral to a specialist allergy clinic.
If there is marked difficulty in breathing or
swallowing, and/or a sudden weakness or floppiness, regard these
as serious symptoms requiring immediate treatment.
If you have suffered a bad allergic reaction in the past -
whatever the cause - then any future reaction may also be
severe. See your GP and request a referral to an NHS allergy
clinic. If you have asthma as well as allergies a referral is
particularly important. Where foods such as nuts, seeds,
shellfish and fish are concerned, even mild symptoms should not
be ignored because future reactions may be severe. This also
applies to drugs, insect stings or latex. Ask your GP to refer
you. Any GP seeking to locate a reputable NHS allergy clinic can
refer to the handbook issued by the British Society for Allergy
and Clinical Immunology (020 8398 9240).
If you suspect you are having, or
might have an anaphylactic attack, SEEK
MEDICAL ASSISTANCE IMMEDIATELY. If you suffer an attack,
and have no medication such as Epinephrine to hand, dial 999
especially nuts, some kinds of
fruit, fish and less commonly spices
anaesthetic drugs, some intravenous infusion liquids, and
things injected during x-rays. Aspirin and other painkillers
(called NSAIDs) can produce very similar reactions.
mainly in rubber latex gloves, catheters, other medical
products, but also in many things encountered in daily life.
Sufferers are nearly always health care workers, mainly
nurses, or have other occupational contact with latex. They
may get anaphylaxis from bananas, avocados, kiwi fruit, figs,
or other fruits and vegetables including even potatoes and
- Bee or wasp (yellow
jacket) stings when
these cause faintness, difficulty in breathing, or rash or
swelling of a part of the body which has not been stung.
If you just get a very large swelling of the part of your body
which was stung, you are probably not going to have
anaphylaxis if stung again.
A substantial proportion of
sufferers have no cause found despite all efforts, even in the
most expert clinics. Doctors call such unexplained attacks
'idiopathic anaphylaxis' The word 'idiopathic' in practice
means we don't know the cause. Worrying as it is, death from
this is very rare indeed. However, there must be a cause or
causes. Some cases are bound to be simple failure to find a
cause and I always regard this diagnosis as provisional, but
if a recognised allergy specialist has given you this label it
is unlikely that another specialist will do any better. The
explanation is NOT psychological in the vast majority. So in
most cases this is a disease for which medical science has not
yet discovered the cause. Some top experts who have studied
hundreds of patients with idiopathic anaphylaxis believe that
it is a disorder of mast cells, causing them to release
histamine and chemicals with similar actions too easily. There
is an excellent book on this condition, quite short, and
intended for doctors and patients. Title: 'Idiopathic
Anaphylaxis', edited by Roy Patterson, Published by OceanSide
Publications Inc, Providence, Rhode Island, 1997, ISBN
may precipitate such reactions in some ('exercise-induced
anaphylaxis'), and so may exercise after food,
sometimes apparently irrespective of what the food is, but in
other people after specific foods. This is called 'exercise-induced
- Medicines called beta
blockers used for
heart disease or high blood pressure can change mild reactions
from another cause into severe anaphylaxis because they block
the body's main defence against anaphylaxis.
- Wrong diagnosis of
proportion (about 10%) of people sent to specialists with a
diagnosis of anaphylaxis have a mistaken diagnosis and have
not had anaphylaxis. If this might be true in your case, it is
well worth finding this out as you may be spared unnecessary
fear and wrong treatment.
Top of page
- Minimise the risk by taking great care and
being vigilant. If you are food allergic, read labels like
Sherlock Holmes: look for the "hidden" allergen. You can
easily recognise a packet of peanuts but may miss the word
"groundnuts" in tiny print on the side of a tin of curry
sauce, or the Latin term arachis used to signify the presence
of peanut in pharmaceutical products.
- If you are food-allergic, be assertive about
asking for detailed information from manufacturers and
- Be particularly careful in restaurants, where
proprietors are under no obligation to list ingredients.
Question staff very directly. It may be necessary to speak
with a senior manager. Some restaurants have ingredient lists
available for you to check. You may wish to telephone the
restaurant in advance to ensure your allergy is taken
- Be alert to all symptoms and take them
seriously. Reach for the adrenaline (epinephrine) if you think
you are beginning to show signs of a severe reaction. Do not
wait until you are sure. Even if adrenaline is administered,
you will still need to get to hospital as soon as possible.
Someone must call an ambulance.
- Make sure others in your family know how to
administer the adrenaline kit - and when. Do not be frightened
of adrenaline. It is a well-understood drug. The dose you will
administer has very few side effects, which will pass quickly
in any case. However, if you have heart difficulties, discuss
these with your doctor.
- Develop a crisis plan for how to handle an
emergency. Get your allergist or GP to help. Have this written
out for family and friends - put it on the bulletin board at
home; carry one in your pocket. If a child is the person at
risk, make sure his teachers and friends' parents have a copy
- along with the adrenaline. Make sure everyone knows where
the adrenaline is when you go out, or when you are at home.
- Wear a Medic Alert talisman (details: 020
- Be open about your allergy problem with your
family, friends and colleagues. It's easy to avoid a Thai,
Chinese or Indian restaurant if everyone knows you are
allergic to peanuts.
Top of page
The treatment for a serious allergic reaction is
adrenaline (also known as epinephrine). During
anaphylaxis, blood vessels leak, bronchial tissues swell and
blood pressure drops, causing choking and collapse. Adrenaline (epinephrine)
acts quickly to constrict blood vessels, relax smooth muscles in
the lungs to improve breathing, stimulate the heartbeat and help
to stop swelling around the face and lips (angioedema).
adrenaline injection kits are available on prescription for
those believed to be at risk. These are available in two
strengths - adult and junior. The injection must be given, as
directed, as soon as a serious reaction is suspected and an
ambulance must be called. If there is no improvement in 5-10
minutes, give a second injection.
Because this must be administered without delay,
patients known to be at risk often carry their own adrenaline
injection kits for use in an emergency.
The injection many doctors prescribe is the
EpiPen, an easy-to-use device with a concealed needle.
The EpiPen is available on prescription and distributed by ALK
-Abelló, 2 Tealgate, Hungerford, Berkshire RG17 0YT. Tel
A relatively new adrenaline injection kit called
Anapen is also available on prescription. It is
manufactured and distributed by Celltech Pharmaceuticals Ltd,
208 Bath Road, Slough, Berkshire SL1 3WE. Tel 01753 447690.
Both companies provide trainer pens for practice
purposes. For information on how to administer the EpiPen
(click here) and Anapen,
It is important to emphasise that even after
adrenaline is administered, medical assistance should be sought
urgently because the effects may wear off after 5 to 10 minutes
and the injection may have to be repeated.
In fact, doctors often prescribe more than one
injection kit so that if medical assistance is delayed, patients
may administer a second dose.
Top of page
Top of page