Medical Oncologist
CION Cancer Clinics
Allergies to declare before anaesthesia | CION Cancer Clinics
Tell your anaesthetist about every reaction you have had to a medicine, latex, antiseptic, plaster, scan dye or food, and about any problem you or a blood relative had with an anaesthetic. You will be given several medicines while asleep and cannot report a reaction yourself. This page lists what to declare, how to tell an allergy from a side effect, and how to get your history ready. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
MI
Medically reviewed by Dr. Mohammed ImaduddinConsultant Surgical Oncologist · MBBS, MS (General Surgery), MCh (Surgical Oncology) · last reviewed September 2026, next review due September 2027
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On this page
- Which allergies should you tell your anaesthetist about?
- What exactly should be on your list?
- Is it an allergy, or a side effect?
- How should you get your allergy history ready?
- What do the allergy words on your forms mean?
- What do people often get wrong about allergies and anaesthesia?
- What if you are not sure what you reacted to?
- Common questions about allergies before anaesthesia
The short answer
Which allergies should you tell your anaesthetist about?
Tell your anaesthetist about every reaction you have ever had to a medicine, latex, antiseptic, plaster or scan dye, and to any food. Also tell them if you or a blood relative ever had a problem with an anaesthetic.
Why it matters more than usual
During an operation you are given many medicines in a short time, often while you are asleep. You cannot say that your lips feel swollen or your skin is itching. The anaesthetist has to plan around your allergies before you fall asleep, not discover them afterwards.
What counts as worth mentioning
More than you might think. A rash from an antibiotic years ago, a swollen eye after a plaster, or an itchy reaction to a dental injection all count. You do not have to decide whether it was a true allergy. Say what happened and let the doctor judge.
Who this matters for most
Everyone having an anaesthetic should answer these questions. It matters most for people who have had a serious reaction before, people with asthma or eczema, and people who have had many earlier operations, procedures or catheters.
This page lists what to declare. It cannot tell you whether you are allergic to something. Only testing and your doctors can.Your checklist
What exactly should be on your list?
Write each one down with what happened and roughly when. A name on a list is useful. A name with the reaction beside it is far more useful.
Antibiotics
An antibiotic is often given just before surgery to prevent wound infection. Reactions to this group are among the most commonly reported.
Names to mention if they caused a reaction
- Penicillin or amoxicillin, including Augmentin
- Cephalosporins, such as cefuroxime or ceftriaxone
- Sulpha medicines
Painkillers
Some people react to common painkillers with wheezing, hives or swelling. This changes what can be given for pain after surgery.
Names to mention
- Aspirin, ibuprofen or diclofenac, such as Voveran
- Morphine, tramadol or codeine
Latex
Latex is found in some gloves, catheters and equipment. If balloons, rubber gloves or condoms make you itch or swell, say so. Many theatres can be set up without latex.
Antiseptics and plasters
Skin cleaners such as chlorhexidine or iodine, like Betadine, and sticky dressings can all cause reactions. A mild rash from a plaster is still worth mentioning.
Scan dye and past anaesthetics
Mention any reaction to contrast dye used in a CT scan. Also mention any problem during or after an earlier anaesthetic, even if nobody explained it to you at the time.
Foods
Tell the team about any food allergy, including egg, soya, nuts, fish or shellfish. Most rarely change the anaesthetic, but the team needs the full picture.
Not sure whether this applies to you?
Ask an oncologistTelling them apart
Is it an allergy, or a side effect?
Sounds more like an allergy
Sounds more like a side effect
Itchy raised rash or hives soon after a medicine
Feeling sick or vomiting after a strong painkiller
Swelling of the lips, tongue, face or throat
Drowsiness or constipation after morphine
Wheezing or trouble breathing
An upset stomach after an antibiotic
Fainting or a sudden drop in blood pressure
Headache or dizziness
Before the day
How should you get your allergy history ready?
Search your old papers
Look through discharge summaries, prescriptions and any allergy card you were given. Photograph the pages on your phone so they travel with you to every appointment.
Ask the family
Ask parents, brothers and sisters whether anyone had a serious problem with an anaesthetic, such as a very high temperature in theatre or waking up very late. Some of these problems run in families.
Say it at the check-up
Tell the anaesthetist at the check-up before surgery. Describe the reaction in your own words, in Telugu if that is easier. Ask for someone to translate if you need it.
Say it again on the day
You will be asked about allergies more than once, and you may be given a coloured wristband. The repetition is a safety check. Answer fully every time.
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On your forms
What do the allergy words on your forms mean?
- Anaphylaxis
- A severe, whole-body allergic reaction that can affect breathing and blood pressure. It needs emergency treatment.
- Intolerance
- An unpleasant effect from a medicine that is not caused by the immune system, such as sickness. It still belongs on your list.
- NKDA
- Short for "no known drug allergies". Check it is correct before anyone writes it in your notes.
- Malignant hyperthermia
- A rare inherited reaction to some anaesthetic gases and one muscle relaxant, causing a dangerous rise in temperature. It is not a cancer, despite the word malignant.
- Allergy testing
- Skin or blood tests done by an allergy specialist to find out which medicine caused a reaction.
Commonly believed
What do people often get wrong about allergies and anaesthesia?
"It was only a small rash, so it is not worth mentioning."
A small reaction tells the team which group of medicines to avoid. It takes a few seconds to say, and it can change which antibiotic or painkiller you are given while you are asleep.
"If I mention an allergy, they will cancel my surgery."
Almost always, the team simply chooses a different medicine or sets up the theatre differently. Hiding an allergy to avoid delay is far more dangerous than the short wait it might cause.
"I am allergic to eggs, so I cannot be put to sleep."
Most people with an egg or soya allergy can have the usual anaesthetic medicines safely. Tell the anaesthetist anyway, so they can make that decision with the full picture.
"The hospital already has my allergies from last time."
Records do not always travel between hospitals, or even between departments. Treat every new team as if they know nothing, and tell them yourself.
Being straight with you
What if you are not sure what you reacted to?
Say that you are not sure. "I had a rash after an injection at a clinic, but I do not know the name" is a useful answer. The anaesthetist would much rather hear something vague than nothing at all.
What the team may do next
They may call the hospital where it happened, ask for old records, or avoid the whole group of medicines to be safe. If the reaction sounds serious, you may be referred to an allergy specialist for testing before surgery. That can move the date, and the anaesthetist will explain why.
If an allergy is found during your operation
Anaesthetists are trained to recognise and treat allergic reactions in theatre. If one happens, you should be told afterwards, given the name of the likely cause in writing, and advised about testing. Keep that letter with your medical papers for the rest of your life.
For the family member helping
If the patient is elderly or unwell, sit in on the check-up. You may remember a reaction they have forgotten.
Questions we are asked
Common questions about allergies before anaesthesia
Do I need to mention allergies I had as a child?
Yes. Some childhood allergies fade, but a note in your history still helps the anaesthetist choose safely. If your parents told you that you reacted to penicillin or another medicine, say so, even if you have never checked it since. The team can decide whether it still matters.
I get hay fever and asthma. Does that count?
Tell the anaesthetist about both. Hay fever alone rarely changes the plan. Asthma matters more, because the anaesthetic and breathing tube affect your airways. Bring your inhalers on the day, and mention whether any painkiller has ever made your breathing worse.
What happens if I have a reaction while I am asleep?
You are watched closely the whole time. The team looks for changes in blood pressure, breathing and skin, and has emergency medicines ready in every theatre. If a reaction happens, it is treated straight away. Afterwards you should be told what happened and advised on testing.
Can I be tested for anaesthetic allergies before surgery?
Routine testing for everyone is not done, because it does not predict reactions well in people who have never had one. Testing is usually offered after a suspected reaction. If you had a serious reaction during an earlier operation, ask whether testing is possible before your cancer surgery.
Should I stop my allergy tablets before surgery?
Do not stop, start or change any medicine on your own. Bring every tablet, inhaler and spray you use, including antihistamines such as cetirizine, to the check-up. The anaesthetist and your prescribing doctor will tell you what to take on the day.
My mother had a bad reaction to anaesthesia. Could it affect me?
Possibly, because a few anaesthetic problems run in families. Find out as much as you can about what happened and tell the anaesthetist. Even a rough description, such as a very high fever in theatre or being slow to wake, is helpful. They may change which medicines they use.
Is iodine or seafood allergy a problem for scan dye?
A seafood allergy does not by itself mean you will react to scan dye or iodine skin cleaner. The real concern is an earlier reaction to the dye or the cleaner itself. Mention both, and let the doctor decide what applies to you.
Should I wear an allergy bracelet?
If you have had a serious allergic reaction, a bracelet or a card in your wallet is sensible. It speaks for you if you cannot. In hospital, you will usually be given a separate allergy wristband as well. Check the names written on it are correct before you go to theatre.
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Sources
- NHS — Anaphylaxis
- NHS — Allergies
- NHS — General anaesthesia
- NICE — Drug allergy: diagnosis and management (CG183)
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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