Hives for more than 6 weeks: why they persist, what to look for, and when the rash may not be ordinary hives

When to call 1669

The NHS hives page, last reviewed on 26 April 2024, says to call 999 if the lips, mouth, throat, or tongue swell suddenly, breathing is very fast or difficult, the throat feels tight or swallowing is hard, the skin, tongue, or lips look blue, grey, or pale, the person is suddenly confused, drowsy, or dizzy, someone faints and cannot be woken, or a child is limp, floppy, or not responding. In Thailand that list uses 1669. It is a different question from itchy hives that already have a clinic visit planned.

The same page also says to seek urgent care if a new rash is not better after 2 days. That line is for a new rash. Two months of hives is not, by itself, a reason to call 1669.

Short answer

Hives for more than 6 weeks are chronic urticaria. A single food is often not the cause. A wheal that lasts beyond 24 hours, hurts, or leaves a bruise needs a clinician to look for another disease. Daily non-sedating antihistamine is the usual start. Do not raise the dose yourself.

Before the visit

Photograph a wheal when it appears, after 6 hours, and after 24 hours. Note whether it faded on its own or left a mark from scratching.

Prepare notes before a chronic-hives visit

After 6 weeks the frame changes

The 2022 EAACI, GA²LEN, EuroGuiDerm, and APAAACI guideline, published in Allergy, defines chronic urticaria as wheals, angioedema, or both for more than 6 weeks, either daily or coming and going. Acute urticaria is 6 weeks or less. AAAAI uses the same cut: less than 6 weeks is acute, and longer than 6 weeks is chronic, with inducible and spontaneous types. DermNet uses a history of more than 6 weeks of wheals that last less than 24 hours, without physical triggers, as part of diagnosing chronic spontaneous urticaria.

The British Association of Dermatologists counts urticaria as chronic when daily or almost daily wheals continue for 6 weeks or more. A second month is therefore not the same task as finding one food behind a short attack. AAAAI says the cause of chronic spontaneous urticaria is often unknown and that it is not usually caused by allergies. The 2021 British guideline says no single cause is found in more than half of acute urticaria and in many people with chronic spontaneous urticaria.

Spontaneous and inducible

The 2022 guideline splits chronic urticaria into spontaneous and inducible disease. Inducible subtypes include symptomatic dermographism, cold, delayed pressure, solar, heat, vibratory, cholinergic, contact, and aquagenic urticaria. One person can have more than one pattern.

AAAAI describes dermatographism along a scratch or under tight clothing, and cholinergic urticaria with sweating or a rise in temperature. Hives after a bath are not proof of an allergy to water. Write down whether the water was hot, whether there was sweat, whether the skin was rubbed, and whether the marks followed a line. An evening pattern is a time to record, not a diagnosis.

A wheal beyond 24 hours, or a bruise

The 2022 guideline says a wheal is fleeting and the skin usually returns to normal within 30 minutes to 24 hours. AAAAI says individual hives usually fade within 24 hours and the skin returns to normal without marks or bruising. DermNet says each chronic spontaneous wheal tends to resolve or change shape within 24 hours. The British guideline says weals generally last up to 24 hours, while angioedema swellings may last up to 72 hours.

A dark mark from scratching until the skin is broken is not the same as one wheal that stays beyond 24 hours and then leaves a bruise. This page does not diagnose from a photograph.

The 2022 guideline separates urticarial vasculitis from urticaria because the mechanism and the tissue picture differ, and vessel-wall necrosis does not occur in urticaria. The British Association of Dermatologists says the weals of urticarial vasculitis are usually prolonged, may be painful rather than itchy, and sometimes leave bruising or a colour change after they fade. Systemic symptoms are often marked, joints or the kidneys may be involved, and inflammatory markers may be high. Confirmation needs a skin biopsy, and the microscope changes are often subtle.

Which tests, and which wide panels to skip

DermNet says the diagnosis rests on the history and the examination. The 2022 guideline recommends a limited basic set: a differential blood count and CRP or ESR. In specialist care it also includes total IgE and IgG against thyroid peroxidase. Further tests follow the history or the examination. The British guideline says to consider baseline tests only when there is a clinical reason, and not to advise routine dietary exclusion. If a detailed history points to a food, investigate that food. TSH and thyroid antibodies may be useful because of an association with thyroid autoimmunity. Chronic hives do not mean every person has thyroid disease.

AAAAI says some cases relate to autoimmunity, including thyroid disease, rheumatoid arthritis, or lupus, usually with other signs such as joint pain or fever. The 2022 guideline describes both IgE autoantibodies against the person’s own targets and autoantibodies that activate mast cells, and it also describes a group whose mechanism is still unknown. That is not the same as saying every person has an autoimmune disease.

The 2022 guideline names NSAIDs as the drugs that most often worsen chronic spontaneous urticaria, in up to one in four patients in that document’s wording. That figure is not the chance for the person reading this page. Tell the clinician about ibuprofen, naproxen, or diclofenac. The same document says paracetamol and COX-2 inhibitors are often better tolerated. Changing a pain medicine is the clinician’s decision.

The medicine ladder belongs to the clinician

The 2022 guideline uses a second-generation, less-sedating H1 antihistamine every day until it is no longer needed, not only when a wheal appears, and recommends against a sedating first-generation antihistamine as routine treatment. The British guideline makes the same strong recommendation and allows a switch to another second-generation drug if the first is unsuitable. This page does not print a dose, and it does not tell a reader to raise a dose, even though a clinician may adjust one second-generation antihistamine under the guideline before other drugs.

If a second-generation antihistamine at the dose the clinician has adjusted is still not enough, the 2022 guideline recommends adding omalizumab, which is licensed for chronic spontaneous urticaria. If that is still not enough, the document suggests considering ciclosporin, which is off-label and has more adverse effects, so it is not a first standard drug. The British guideline offers omalizumab added to an antihistamine when first-line options fail, and says not to use long-term systemic corticosteroids unless there is no other option. A short course of a few days can be a rescue for a severe flare in that document. It is not a standing daily treatment.

The AAAAI page dated 18 June 2026 also names dupilumab and remibrutinib as approved options in some chronic-urticaria settings. Those two names are not steps in the 2022 three-step algorithm, so they are not folded into one recipe. The clinician chooses. The same page says about half of people with chronic spontaneous urticaria respond to antihistamines as that page describes, and that among those who do not improve, 65 in 100 respond to omalizumab. It also says half improve within 1 to 2 years and 80 to 90 in 100 within 5 years, and that hives can return. Those figures describe groups on that page, not one person’s timetable.

The aim in the 2022 guideline is to be free of signs until the disease remits on its own, not to wait it out untreated.

Questions for the visit

Do these hives meet the definition of chronic urticaria?
Are they spontaneous, inducible, or both?
Does each wheal fade within 24 hours?
Is a dark mark from the wheal itself or from scratching?
Is there a reason to suspect urticarial vasculitis, and is a biopsy needed?
Do heat, warm water, sweat, exercise, scratching, or pressure trigger the rash?
Has there been swelling of the lips, eyelids, or face?
Which tests are useful, and which are not needed?
Is a broad food-allergy panel needed?
Could a current medicine, especially an NSAID, be worsening the hives?
Is the antihistamine suitable for chronic urticaria, and should it be taken every day?
If control is poor, what is the next step?
Is there a reason to test the thyroid or look for autoimmune disease?
Which symptoms mean calling 1669?
Should symptoms be tracked with UAS7 or the Urticaria Control Test?

What to bring

The start date, and photos at onset, at 6 hours, and at 24 hours
How long each wheal lasts, whether it moves, and what mark remains
Whether itch, burning, or pain dominates, and any swelling of the lips, eyes, or face
What came first, such as a hot bath, sweat, exercise, tight clothes, or pressure, plus any suspected food and the time after eating
Every medicine, including NSAIDs and supplements, the antihistamine name, and whether it is taken daily or only when itchy
Fever, joint pain, abdominal pain, and any personal or family thyroid or autoimmune disease

What the wheal is saying

Feature	Fits ordinary hives?	What else to consider
Wheal fades within 24 hours and leaves no mark	Fits	Chronic urticaria if this has lasted more than 6 weeks
The same wheal lasts beyond 24 hours	Outside the usual wheal definition	A clinician should separate vasculitis and other diseases
Marked itch	Common	Still check how long each wheal lasts
Pain or burning dominates itch	Not the usual picture of an ordinary wheal	Needs a further look, including vasculitis
Leaves a bruise or a purple mark	AAAAI says ordinary hives do not leave a bruise	Separate a scratch mark from a mark left by the wheal
Appears along a scratch	Can fit dermatographism	Inducible urticaria
Appears after heat or sweat	Can fit cholinergic or heat-related urticaria	Do not conclude an allergy to water

How the author lined this up

Asst. Prof. Dr. Norawit Raatpiboon separated three facts that a story often merges. The 2022 guideline uses 6 weeks as the line for chronic urticaria and 24 hours as a feature of an ordinary wheal. AAAAI and DermNet use that same wheal window. The British Association of Dermatologists says prolonged, painful weals that leave bruising raise urticarial vasculitis, which a biopsy confirms, not a photograph alone.

A widespread itchy rash with a past voice change and anaphylaxis warning is a Thai page about a severe allergic reaction, not the answer to two months of hives.
Hives after switching a hormone tablet asks whether the new medicine is involved.

Common questions

What are hives called after 6 weeks?

The 2022 guideline and AAAAI call this chronic urticaria when wheals, angioedema, or both last more than 6 weeks, either daily or coming and going.

Does chronic urticaria mean a food allergy?

Usually no. AAAAI says chronic spontaneous urticaria is not usually caused by allergies. The British Association of Dermatologists does not advise routine food exclusion. Test further only if one food is followed, more than once, by hives in a related time window.

Why did allergy tests find nothing?

Many people with this disease have no single trigger for a food panel to find. A broad allergy panel without a guiding history is not the first step in the 2022 guideline.

Why do hives appear at night?

The clock time alone does not name a cause. DermNet says wheals may come at certain times of day. Record the time for the clinician, together with heat, sweat, and scratching.

Do hives after a bath mean an allergy to water?

Not yet. Water is the trigger of aquagenic urticaria, which is uncommon. Heat, sweat, rubbing, and tight clothing are different patterns. Write the details before drawing a conclusion.

How long should one hive last?

The 2022 guideline says the skin usually returns to normal within 30 minutes to 24 hours. AAAAI and DermNet also use 24 hours. Angioedema can last longer, up to 72 hours.

Can hives still be hives if they leave a dark mark?

A mark from scratching can happen, but AAAAI says an ordinary hive does not leave a mark or a bruise when it fades. If the same wheal lasts beyond 24 hours and then leaves a bruise, a clinician should look. A photograph is not the diagnosis.

How is urticarial vasculitis different from hives?

The British Association of Dermatologists says the weals are usually prolonged, may hurt more than they itch, and sometimes leave bruising. Confirmation uses a biopsy, not a dark mark alone.

Which blood tests are needed?

The 2022 guideline limits the basic set to a differential blood count and CRP or ESR. Specialist care may add total IgE and antibodies to thyroid peroxidase. The British Association of Dermatologists tests when there is a reason, not one panel for every person.

Should an antihistamine be taken every day?

The 2022 guideline uses a less-sedating second-generation H1 antihistamine every day to prevent wheals, not only when they appear, as the main plan. The dose belongs to the clinician.

What if an antihistamine is not enough?

There is a next step. The 2022 guideline moves to omalizumab and then considers ciclosporin if that is not enough. The 2026 AAAAI page also names dupilumab and remibrutinib. Choice and dose belong to the clinician. This page does not tell anyone to add a drug.

Is a thyroid test required?

Not for every person in every clinic. The 2022 guideline places thyroid antibodies in the specialist set. The British Association of Dermatologists says the test may be useful because of an association. Chronic hives do not mean every person has thyroid disease.

When is this an emergency?

Sudden swelling of the lips, tongue, or throat, trouble breathing, trouble swallowing, confusion, fainting that cannot be woken, or a limp child means calling 1669, using the NHS list. Chronic hives that already have a follow-up visit are not that list.

Sources opened for this page

What this page does not do

This page is general information from sources opened for it. It does not diagnose from a photograph, print a dose, or tell a reader to raise an antihistamine, omalizumab, or ciclosporin. If a dark mark or a long-lasting wheal raises another disease, a clinician examines it.