Hives: What to Do Now & When to Call 115

Key takeaways

The giveaway with hives is that they travel: each individual weal lasts only a few hours then fades completely, leaving no mark, while new ones appear somewhere else.
Hives together with swelling of the lips or tongue, difficulty breathing, difficulty speaking, vomiting with severe abdominal pain, or faintness is anaphylaxis — call 115 immediately; this is no longer a skin problem.
The most useful thing to do at home is photograph the rash while it is up and write down what was eaten and what medicine was taken beforehand. The rash will have faded before you reach a doctor.
Do not apply crushed leaves or warming balms, do not buy injections to stop the itching, and do not eat or drink the suspected trigger again to see whether it really was the cause.

Hives are mostly harmless: raised, itchy weals that settle by themselves. But the same kind of rash is also the skin sign of anaphylaxis, a severe allergic reaction that develops within minutes. So the first thing to do is not to stop the itching — it is to check for swelling of the lips, difficulty breathing, difficulty speaking, vomiting or faintness. If any of those is present, call 115 (the emergency number in Vietnam) immediately.

Recognising hives

The weals stand up off the skin like mosquito bites but larger, pink-red, sometimes paler in the centre, and very itchy. The surest sign is not the shape but the way they move: each weal lasts a few hours then fades completely, and new ones appear elsewhere.

Each spot fades within a day, the skin where it was looks normal again, with no scaling and no mark left behind; press on a weal and the pressed area goes white
There may be only a few spots, or they may merge into large patches with a wandering map-like border; the more you scratch, the more come up
A test you can do yourself: draw a pen outline around one weal. If the weal has moved out of the outline a few hours later, it is hives; if it sits in exactly the same place for more than a day, a doctor should look at it

When hives are a sign of anaphylaxis

Anaphylaxis does not only follow bee stings or injections. It opens exactly like an outbreak of hives, and only minutes later comes the difficulty breathing. A rash that spreads rapidly over the whole body after food, after a medicine or after a sting is the situation to watch.

Call 115 NOW, do not wait to see whether it eases, if hives come with any of the following: swelling of the lips, the face or the tongue, or a feeling of tightness in the throat; difficulty breathing, wheezing, a hoarse voice, difficulty speaking; vomiting, severe abdominal pain or sudden diarrhoea at the same time as the rash; faintness, collapse, heavy sweating, pale cold skin; a child who is drowsy, refusing to feed, or blue around the lips. While you wait: lay the person down and raise their legs, do not let them sit up or walk about; if they are vomiting, lay them on their side. Anyone who has been prescribed an adrenaline auto-injector by a doctor should use it exactly as they were instructed, and still call 115 — after using it you must still get to a medical facility, because the symptoms can come back.

What hives are mistaken for

Mistaken for	The difference you can see
Mosquito or insect bites	The spot stays in exactly the same place for days, often with a puncture point in the middle
Contact dermatitis	Exactly matches the area of skin that touched something, does not move, and scales afterwards
A viral rash	Flat rash, spreads in a set order, often with a fever, does not move
Angioedema	Deeper swelling of the lips, eyelids, hands; feels tight rather than itchy, and settles slowly

The most useful distinguishing feature is time: hives change position within the day, the other rashes do not.

What to do now, at home

Hives are a reaction from the inside, so what you do at home has only two aims: ease the itching and find the trigger. None of the following needs a prescription.

Stop whatever you suspect straight away: the dish just eaten, the medicine just taken. For medicines treating an underlying condition, ask the doctor before stopping.
Photograph the rash while it is up and write down everything eaten, drunk, injected or applied in the previous half day — the rash will have faded before you get to the clinic.
Cool compresses with a damp cloth, a cool shower, loose soft clothing; cut fingernails short and try not to scratch.
Stay with the person during the first few hours, particularly if the rash came up after food or after a medicine.

What not to do

Do not apply herbal bath preparations, limewater, toothpaste, warming balms or alcohol: hives come from the inside out, so applying something on the surface does not solve it and easily adds contact dermatitis
Do not buy injections or itch-stopping tablets over the counter, and do not use a medicine prescribed for someone else; several of those products contain corticosteroids
Do not eat or drink the suspected trigger again to see whether it really was the cause — the reaction can be worse next time
Do not use herbal steaming, hot compresses or heavy covers — heat and sweat bring up more weals

Doctors commonly use antihistamines, with oral corticosteroids added in a severe episode; someone with a history of anaphylaxis may be prescribed an adrenaline auto-injector to carry. Which medicine and for how long is the doctor's decision. Aspirin and ibuprofen make hives worse in some people; paracetamol (acetaminophen) is generally used, but the dose is for the doctor or pharmacist to decide.

When you must go to hospital

Call 115 immediately if there are signs of anaphylaxis: swelling of the lips or tongue, difficulty breathing, difficulty speaking, vomiting with severe abdominal pain, faintness. — Be seen TODAY if: the lips or eyelids are swollen even without difficulty breathing; the rash came up after taking a medicine, antibiotics or painkillers especially; the rash comes with fever or joint pain; you have had hives after a bee sting or an injection before; or the patient is a young child, a pregnant woman or someone with an underlying condition. — Be seen within 24–72 hours if: a spot stays in exactly the same place for more than a day, or fades leaving a bruise; the rash keeps returning in waves for no clear reason; or the hives have lasted more than six weeks. — If you are not sure, call and ask before deciding on your own.

What can be done at home, and when you need a medical facility

Most episodes of acute hives can be watched at home, as long as the family knows the exact point at which to call 115 and does not apply or inject anything. At home, Y Te Xanh (GreenCare) can: have a doctor look at the rash or at the photographs you took, go back over medicine and food history to narrow down the trigger, and have a nurse carry out what the doctor has prescribed. What needs a medical facility: any case with signs of anaphylaxis, throat swelling or difficulty breathing, and chronic hives that need the cause investigated.

According to CDC, hives are one of the signs of a severe allergic reaction, along with swelling of the face and throat, difficulty breathing, a fast heartbeat, faintness or weakness; if you see those signs you must call for emergency help straight away. Citing CDC here does not imply that CDC endorses Y Te Xanh or our services.

Need personalised advice for your loved one? Call our hotline 094 368 81 15 (24/7) — calling to ask a question or to book costs nothing. GreenCare has doctors who come to examine, nurses who carry out doctor's orders (injections, infusions, dressing changes), remote consultation by video call, and a review of the medicines you are taking; an in-depth remote consultation, or any one after the first, is a paid service. For children we take examination and acute care only — not long-term care at home, and not newborns or expectant mothers. We confirm we have staff in your area and provide transparent pricing before we begin.

Sources

NHS — Hives
NHS — Anaphylaxis

Frequently asked questions

How long do hives last?

Each individual spot lasts only a few hours then fades, but an episode of hives can run for a few days to a few weeks because new spots keep coming up. If the pattern of coming and going lasts more than six weeks it is considered chronic hives, and at that point you should be seen rather than continuing to manage it yourself.

Are hives contagious?

No. Hives are that person's own reaction; they do not pass to anyone else through contact or shared items. However, if the episode started after a viral infection — very common in young children — then it is the infection itself that is contagious, not the rash.

Can you bathe with hives?

Yes, and you should, in cool or just-warm water, without scrubbing. Clean, cool skin itches less. Avoiding washing and then wrapping up warmly is the way to bring up more weals, because heat and sweat are both triggers for hives in many people.

Does it matter if we never find the cause?

It is very common, chronic hives especially: in most cases no specific trigger can be identified. That does not mean ignoring it. Keep a note of each episode along with the food, medicines and activities that came before it, and take that to the appointment — that diary is more useful than running tests broadly.

What should I do if hives came up after taking a medicine?

Stop the suspected medicine and contact a doctor, unless it is treating an underlying condition, in which case ask before stopping. Write down the name of the medicine, keep the box or the prescription to take with you, and do not try it again yourself. If there is swelling of the lips or difficulty breathing, call 115 immediately.

I come out in hives whenever it turns cold or I sweat — is that a weather allergy?

That is the everyday name for it, but more precisely this is the group of hives triggered by physical factors: cold, heat, sweat, pressure, sunlight, exertion. Let a doctor identify which one, because cold-induced hives can cause a severe reaction when the whole body is immersed in cold water — worth knowing before you swim in the sea or in a stream.