Wasp and Bee Stings
A whole arm swelling up is frightening and usually harmless. What actually separates a big local reaction from a dangerous one is where the symptoms are, not how bad they look.
Part of the Complete Insect Bites Guide.
Key fact: A sting that swells dramatically over a day or two — a whole forearm, an eye closed over — is usually a large local reaction, not an allergy. It looks far more alarming than it is. A dangerous reaction affects the whole body and starts within minutes, not hours.
The first few minutes
- Move away calmly from where it happened. Wasps in particular can sting repeatedly, and a crushed wasp releases a chemical that attracts others.
- Remove the sting if one is visible — immediately, and by whatever method is quickest.
- Wash the area with soap and water.
- Apply something cold for ten to twenty minutes. This does more for pain and swelling in the first hour than anything else.
- Raise the limb if it is an arm or leg, which limits how much it swells.
- Take off rings, watches and tight sleeves before swelling sets in. This is the step people wish they had taken.
Getting the sting out
Only honeybees leave a sting behind. The barbed sting tears away from the bee along with the venom sac, which continues to pump venom for a short time after the bee has gone. Wasps and hornets have smooth stings, withdraw them cleanly, and can sting again — so if there is no sting visible, it was probably not a bee.
Speed matters more than technique. There is a long-standing instruction to scrape a sting out rather than pinch it, on the theory that pinching squeezes in more venom. The evidence does not support the distinction — what matters is how quickly the sting comes out. Use a fingernail, a bank card, tweezers, whatever is to hand, and do it now rather than looking for the right tool.
What a normal reaction looks like
An ordinary sting produces immediate sharp pain, then a red, raised, hot area a few centimetres across, itching, and swelling that settles over a few hours to a couple of days. That is the expected response to venom and needs nothing beyond a cold compress, and if it is uncomfortable, an antihistamine and paracetamol or ibuprofen.
Stings hurt more than bites and stay sore longer. Pain alone, even considerable pain, is not a sign of anything going wrong.
Large local reactions
Around one person in ten has an exaggerated reaction at the site: swelling that keeps going well beyond the sting, often more than 10cm across, sometimes involving the whole forearm, the whole hand, or closing an eye.
| Large local reaction | |
|---|---|
| When | Builds over 24 to 48 hours, rather than minutes |
| Where | Confined to the stung limb or area — it spreads outwards from the sting, not to other parts of the body |
| How long | Can take up to a week to settle fully |
| Feels | Hot, tight, itchy and uncomfortable — but you are otherwise well |
| Treatment | Cold compress, elevation, an antihistamine, and simple painkillers. A short course of oral steroid is occasionally prescribed for a severe one |
| Does it mean allergy? | No. A large local reaction does not mean the next sting will cause anaphylaxis |
The part that causes confusion: a large local reaction at 48 hours is red, hot, swollen and tender — which is also how infection is described. Infection is uncommon after a sting and rarely appears this early. Swelling that peaks around 48 hours and then improves is the reaction; swelling that is still worsening on day four, or comes with fever or spreading redness, is worth having looked at.
Telling a big swelling from an allergy
This is the distinction that matters, and it is simpler than people expect. It is not about how much swelling there is. It is about where and how fast.
| Large local reaction | Systemic allergic reaction | |
|---|---|---|
| Timing | Hours to days | Minutes, usually within 30 |
| Location | Around the sting only | Away from the sting — face, chest, elsewhere |
| Skin | One swollen area | Widespread hives, flushing or itching all over, including palms and soles |
| Breathing | Normal | Wheeze, cough, tight chest, difficulty breathing |
| Throat and mouth | Normal | Swelling of lips, tongue or throat; hoarse voice; difficulty swallowing |
| How you feel | Sore and fed up, but well | Faint, dizzy, clammy, a sense of something being badly wrong |
| Gut | Normal | Sudden cramping, vomiting or diarrhoea |
One swollen arm and an otherwise normal person is a local reaction, however dramatic it looks. Any symptom away from the sting shortly after being stung is different in kind.
When it is an emergency
Call 999 immediately if, after a sting, there is: difficulty breathing, wheeze or noisy breathing · swelling of the lips, tongue, throat or face · a hoarse voice or difficulty swallowing · a widespread rash or hives · feeling faint, dizzy or collapsing · sudden severe abdominal pain or vomiting. If an adrenaline auto-injector is available, use it without waiting — into the outer thigh, through clothing if necessary — then call 999 and lie the person flat with their legs raised. Use a second device after five minutes if there is no improvement.
Two situations warrant 999 regardless of how the person seems: a sting inside the mouth or throat, where local swelling alone can obstruct the airway, and many stings at once, where the total venom dose can cause problems without any allergy being involved.
After a bad reaction
Anyone who has had a systemic reaction to a sting — symptoms away from the site — should be referred to an allergy service. Two things follow from that assessment.
- Adrenaline auto-injectors, with training for the person and those around them, and a written plan.
- Venom immunotherapy — a course of gradually increasing doses over about three years, which is highly effective at reducing the risk of a further severe reaction. It is one of the more successful allergy treatments and is under-used.
A large local reaction does not require any of this, and does not indicate a risk of anaphylaxis next time. If you are uncertain which you had, describing where the symptoms were — at the sting, or elsewhere — is what settles it.
Frequently Asked Questions
My whole arm swelled up after a wasp sting. Am I allergic?
Probably not. Swelling that spreads outwards from the sting over 24 to 48 hours and stays confined to that limb is a large local reaction, which affects around one person in ten and does not indicate allergy. A dangerous reaction produces symptoms away from the sting — widespread hives, breathing difficulty, throat or tongue swelling, faintness — and begins within minutes rather than hours.
Should I scrape a bee sting out rather than pull it?
Speed matters far more than technique. The long-standing advice to scrape rather than pinch is not well supported by evidence, and the time spent finding something to scrape with allows more venom to be delivered. Remove it immediately by whatever means is quickest — fingernail, card, tweezers. Only honeybees leave a sting behind; wasps withdraw theirs cleanly and can sting again.
How long does a wasp sting take to settle?
An ordinary reaction settles over a few hours to a couple of days. A large local reaction builds for 24 to 48 hours and can take up to a week to resolve completely. Swelling that is still worsening on day four, or that comes with fever or redness spreading well beyond the swollen area, is worth having assessed rather than waiting out.
Is a swollen, hot, red sting on day two infected?
Usually not. Infection after a sting is uncommon and rarely appears that quickly — a large local reaction at 48 hours is red, hot, swollen and tender, which is exactly how infection gets described. The useful distinction is direction of travel: a reaction peaks around 48 hours and then improves, whereas infection continues to worsen after that, often with fever.
What should I do if someone is stung in the mouth?
Call 999. A sting inside the mouth or throat warrants emergency assessment even without any allergy, because local swelling in that location can obstruct the airway. The same applies to a large number of stings at once, where the total dose of venom can cause problems independently of any allergic reaction. While waiting, keep the person upright and give them something cold to suck if they can swallow safely.
References
- NHS. Insect bites and stings. nhs.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Insect bites and stings. cks.nice.org.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Urticaria. cks.nice.org.uk
- Resuscitation Council UK. Emergency treatment of anaphylaxis. resus.org.uk
- DermNet. Papular urticaria, bullous insect bite reactions and urticaria. dermnetnz.org
- UK Health Security Agency. Bed bugs and public health. gov.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. A severe allergic reaction to a sting is a medical emergency — difficulty breathing, swelling of the lips, tongue or throat, a widespread rash or feeling faint after a sting means calling 999 immediately. Always consult a qualified healthcare professional for diagnosis and treatment.