Insect stings and allergic reactions

Most reactions are not allergic

A sting from a bee, wasp or hornet hurts immediately, produces a red swollen lump, and settles over a few hours to a few days. That is the normal response to venom, and it happens to everyone. It is not an allergy.

Only a small minority of people develop a genuine allergic reaction to stings, and a smaller number again have anaphylaxis. This is worth stating plainly, because older writing on the subject tends to imply the opposite and leaves people frightened of an outcome that is uncommon.

Some groups are at higher risk, mostly through repeated exposure: beekeepers, gardeners and refuse collectors among them. Having hay fever or a food allergy does not raise the risk of a sting allergy, which surprises people.

Getting the sting out

One point here is routinely got wrong, including by the version of this article that stood here before.

Honeybees have a barbed sting. It tears away from the bee and stays in the skin, still attached to the venom sac, which continues to pump. Getting it out quickly is what matters.

Wasps and hornets have smooth stings. They withdraw them and can sting again, and they do not normally leave anything behind. Looking for a wasp sting in the skin is usually looking for something that is not there.

Where a sting is visible, scrape it out sideways with a fingernail or the edge of a bank card. Do not use tweezers or pinch it, because squeezing the sac forces in more venom. Then wash the area with soap and water.

Ordinary self-care

For a normal reaction, the measures are simple:

• a cold pack wrapped in cloth, or a cold damp cloth, held on for at least twenty minutes
• keeping the area raised where that is possible
• paracetamol or ibuprofen for the pain
• an antihistamine for itching, and hydrocortisone cream for itching and swelling
• not scratching, which is how these become infected

A pharmacist can advise on all of the above without an appointment.

Home remedies such as bicarbonate of soda are not worth bothering with.

Large local reactions

Between the ordinary lump and anaphylaxis sits a third thing, and knowing it exists saves a good deal of alarm.

A large local reaction is swelling of more than about ten centimetres at the site, which typically continues to grow over the following day or two. A sting on the forearm can swell most of the forearm. It looks dramatic and it is not dangerous.

Someone who reacts this way will probably react similarly to future stings, and carries a slightly raised chance of a systemic reaction, so it is worth mentioning to a GP — but it is not an emergency and it is not anaphylaxis.

The distinction is location. A large reaction confined to the area around the sting is local. Symptoms appearing somewhere else entirely — swelling of the face when the sting was on the leg, a rash across the body, difficulty breathing — mean the reaction has gone systemic, and that is the next section.

When it is anaphylaxis

Call 999 if, after a sting, any of these appear:

• the lips, mouth, throat or tongue suddenly swell
• breathing is very fast or difficult, with wheezing, choking or gasping
• the throat feels tight, or swallowing becomes difficult
• the skin, lips or tongue turn blue, grey or pale — on darker skin this may show first on the palms or soles
• someone becomes suddenly confused, drowsy or very dizzy
• someone faints and cannot be woken
• a child goes limp, floppy or stops responding as they normally would

The order of what happens next matters, and older advice gets it backwards by listing antihistamines first.

1. Use the adrenaline auto-injector immediately, if there is one, following the instructions on the device.
2. Lie the person flat with their legs raised. Standing or sitting them up can make things worse.
3. Call 999 and say the word anaphylaxis.
4. If there is no improvement after five minutes, give a second dose from a second device.

Adrenaline is the treatment. Antihistamines and steroid creams are not, and waiting to see whether an antihistamine works is the delay that causes harm. Nor is improvement a reason to stand down: reactions can return after appearing to settle, which is why the ambulance is called even when someone seems to recover.

Carrying adrenaline

Anyone who has had a systemic reaction to a sting should be assessed and will usually be prescribed adrenaline auto-injectors.

Two points about them. They are prescribed in pairs, and the guidance is to carry two in-date devices at all times, precisely because a second dose is sometimes needed. And the time to learn how one works is not during an emergency — trainer devices exist, manufacturers publish videos, and the people around the person should know where the devices are kept.

When to get it looked at, without it being an emergency

Contact a GP or NHS 111 after a bite or sting if:

• symptoms are getting worse, or are not improving
• the sting was in the mouth or throat, or near the eyes
• there is stomach pain and vomiting
• there is dizziness or light-headedness
• a large area around the site is red and swollen
• there is a high temperature and swollen glands
• there were multiple stings
• there has been a serious reaction to a sting before

Bites, and ticks in particular

Biting insects — mosquitoes, midges, horseflies, fleas and mites — produce itching and local swelling rather than the sharp venom reaction of a sting, and the same self-care applies.

Ticks deserve separate mention, because the method of removal matters and because of what they can carry.

Use fine-tipped tweezers or a tick-removal tool, grip the tick as close to the skin as possible, and pull upwards slowly and steadily without squeezing or twisting the body. Check that no mouthparts are left behind, then clean the area with antiseptic or soap and water.

A spreading circular or bullseye-shaped rash in the days or weeks after a tick bite can indicate Lyme disease, and needs a GP appointment rather than watchful waiting.

Spiders

Spiders are not insects, and in Britain they are a much smaller problem than American writing on this subject suggests.

Bites are uncommon, since spiders avoid contact, and they are rarely medically serious here. The alarming accounts of bites causing areas of dying tissue describe species found in parts of North America, not in the UK.

What is worth watching for is ordinary infection, which can follow any break in the skin: an area that becomes increasingly red, hot, painful or swollen over the days after a bite, particularly with a temperature, should be seen.

The treatment that changes the allergy

For someone who has had a severe allergic reaction to a sting, there is a treatment that addresses the allergy itself rather than the next reaction.

Venom immunotherapy is a course of injections of the venom, starting very low and building up, given at an allergy clinic over about three years. It is among the most effective applications of immunotherapy there is — reported protection against further serious reactions is in the region of 95% or better for wasp venom and somewhat lower for bee.

For a gardener or beekeeper who has had anaphylaxis, that is the difference between avoiding the outdoors and getting on with life. It needs a GP referral to an allergy clinic.