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Hives
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In one pass Hives, or urticaria, happen when mast cells in the skin suddenly release histamine and other substances: a small patch of blood vessels widens and leaks plasma, and the skin rises into a sharply edged, itchy bump called a wheal, often ringed with redness.
Educational content, not medical advice — consult a clinician.
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Chapter 1
What hives are
Hives, or urticaria, happen when mast cells in the skin suddenly release histamine and other substances: a small patch of blood vessels widens and leaks plasma, and the skin rises into a sharply edged, itchy bump called a wheal, often ringed with redness. Hives come fast and go fast. A single wheal usually fades within 30 minutes to 24 hours and the skin returns to normal, but new ones can appear elsewhere, so the rash seems to move around.
Hives are common: an international guideline estimates that about 20% of people have acute hives at some point in life. Hives that last 6 weeks or less are called acute; they often follow a cold, a food or a medicine, though in about half of cases no cause is found. Hives that last more than 6 weeks are called chronic. The kind that appears on its own usually has no outside cause, and in more than half of these people it is tied to the immune system attacking the body itself.
One situation cannot wait a minute: if hives come with swelling of the lips, tongue or throat, a tight throat, trouble breathing, or feeling faint, this may be anaphylaxis, a severe allergic reaction. Call emergency services now; what to do is in When to get emergency or medical help.
Hives are common: an international guideline estimates that about 20% of people have acute hives at some point in life. Hives that last 6 weeks or less are called acute; they often follow a cold, a food or a medicine, though in about half of cases no cause is found. Hives that last more than 6 weeks are called chronic. The kind that appears on its own usually has no outside cause, and in more than half of these people it is tied to the immune system attacking the body itself.
One situation cannot wait a minute: if hives come with swelling of the lips, tongue or throat, a tight throat, trouble breathing, or feeling faint, this may be anaphylaxis, a severe allergic reaction. Call emergency services now; what to do is in When to get emergency or medical help.
Clinical · Wheals versus angioedema
An international guideline gives a wheal three features:A sharply edged, superficial swelling in the middle, of any size or shape, almost always ringed with redness.Itching, or sometimes a burning feeling.A fleeting life: the skin usually returns to normal within 30 minutes to 24 hours, without a scar.
When the same reaction happens deeper, in the lower skin, the tissue beneath it or the moist lining of the body, it is called angioedema: a sudden, deep swelling that is red or skin-colored. It tends to tingle, burn, feel tight or sometimes hurt rather than itch, and it fades more slowly, taking up to 72 hours. About 40% of people with hives also get angioedema.
On brown and black skin the redness can be hard to see, and the raised patches are easier to spot.
Hives are not eczema. A single wheal is gone within a day; eczema runs on a different mechanism that starts with a skin barrier that cannot hold water (see Inflammatory skin disease).
weidinger-2018-atopic
Chapter 2
How a wheal rises
Mast cells sit in the skin and the body's moist linings. They are packed with granules, and their surface carries receptors that grip IgE antibodies tightly. Once activated, a mast cell degranulates: it empties out histamine together with platelet-activating factor, leukotrienes and prostaglandins. In the skin these substances do three things:
They stimulate sensory nerves, so the skin itches.They widen small blood vessels, so it turns red.They make the small veins just after the capillaries leaky, so plasma seeps into the upper and middle layers of the skin and a wheal rises; when it seeps into the deeper layer, the result is angioedema.
Four to 8 hours later, the mast cell releases a second wave of inflammatory signals, which may deepen the inflammation and make the rash last longer.
More than one thing can flip this switch. An allergen recognized by the IgE on the cell's surface is one route. Some medicines can trigger hives without IgE, such as painkillers like ibuprofen, and mast cells carry other receptors as well (one is called MRGPRX2). In chronic hives the switch is often an antibody the body makes against itself; see Chronic hives with no outside cause.
They stimulate sensory nerves, so the skin itches.They widen small blood vessels, so it turns red.They make the small veins just after the capillaries leaky, so plasma seeps into the upper and middle layers of the skin and a wheal rises; when it seeps into the deeper layer, the result is angioedema.
Four to 8 hours later, the mast cell releases a second wave of inflammatory signals, which may deepen the inflammation and make the rash last longer.
More than one thing can flip this switch. An allergen recognized by the IgE on the cell's surface is one route. Some medicines can trigger hives without IgE, such as painkillers like ibuprofen, and mast cells carry other receptors as well (one is called MRGPRX2). In chronic hives the switch is often an antibody the body makes against itself; see Chronic hives with no outside cause.
Mechanism · What antihistamines block
Histamine has to land on its H1 receptor to work. Antihistamines occupy that receptor and hold it in its inactive state, so there is less itching and fewer wheals. That is why an international guideline strongly recommends a second-generation antihistamine as the first step for every type of hives; the older kind makes people clearly drowsy and impairs driving, and the guideline recommends against using it as the first choice.It also shows where antihistamines fall short. Mast cells release more than histamine, and in anaphylaxis, mast cells and basophils throughout the body release these substances at once, reaching the airways and blood pressure. Antihistamines then play only a limited role and can ease only the skin symptoms; the first-line drug is adrenaline (epinephrine) injected into a muscle. So if your throat feels tight or you are struggling to breathe, do not take an allergy tablet and wait: call emergency services now.
Chapter 3
What sets off acute hives
The most common causes of acute hives (lasting up to 6 weeks) are medicines, foods and viral infections; others include stress, parasite infections, insect venom and allergens that touch the skin. An international guideline points out that acute hives often follow an upper airway infection, such as a common cold, and COVID-19 counts too.
Foods: the most common are milk, eggs, peanuts, tree nuts, fish and shellfish, acting through an IgE-driven allergy.Medicines: drugs like penicillin act through IgE; nonsteroidal anti-inflammatory drugs () such as ibuprofen and aspirin can trigger hives without IgE.
Yet in about half of acute hives, no cause is ever found. Because acute hives clear up on their own, the guideline recommends against routine tests: a careful history is enough, and allergy testing is needed only to confirm a suspected food or drug allergy. Of the acute cases with no cause found, up to 36% later turn chronic.
Foods: the most common are milk, eggs, peanuts, tree nuts, fish and shellfish, acting through an IgE-driven allergy.Medicines: drugs like penicillin act through IgE; nonsteroidal anti-inflammatory drugs () such as ibuprofen and aspirin can trigger hives without IgE.
Yet in about half of acute hives, no cause is ever found. Because acute hives clear up on their own, the guideline recommends against routine tests: a careful history is enough, and allergy testing is needed only to confirm a suspected food or drug allergy. Of the acute cases with no cause found, up to 36% later turn chronic.
In practice · When you suspect a food or drug
If wheals keep appearing soon after a particular food or medicine, write it down: what you had, how long before, and where the hives came up. Photos help, so take some to show the doctor. An allergist can confirm the link with skin prick tests or a blood test for specific IgE, and the results are best read by an experienced doctor.Once a trigger is confirmed, avoid it strictly, ideally with written instructions on how. Another exposure could cause not just hives but anaphylaxis.
On the other hand, without such a clear before-and-after link, there is no need to order a large allergy panel yourself: for acute hives, the international guideline recommends against routine tests like these.
Chapter 4
Chronic hives with no outside cause
Wheals that keep coming and going for more than 6 weeks are chronic hives. There are two kinds. One has a definite trigger, such as cold, scratching or a rise in body temperature, and is called inducible. The other has no definite trigger and appears on its own; it is called chronic spontaneous urticaria. Going by health-system data from different countries, between 0.1% and just under 1% of people have chronic hives at any one time; women are affected at least twice as often as men, and most patients are over 20.
The spontaneous kind has no outside cause because the switch is inside the body. The international guideline states that more than half of chronic spontaneous urticaria is driven by two autoimmune mechanisms:
Autoallergy (type I): the body makes IgE antibodies against its own proteins, such as thyroid peroxidase, so mast cells treat the body's own protein as an allergen.Type IIb: the body makes IgG antibodies that grab the IgE on the mast cell's surface, or its receptor, setting the mast cell off again and again.
Some people have both. About 27% of patients carry antithyroid antibodies, so doctors often check thyroid markers.
The spontaneous kind has no outside cause because the switch is inside the body. The international guideline states that more than half of chronic spontaneous urticaria is driven by two autoimmune mechanisms:
Autoallergy (type I): the body makes IgE antibodies against its own proteins, such as thyroid peroxidase, so mast cells treat the body's own protein as an allergen.Type IIb: the body makes IgG antibodies that grab the IgE on the mast cell's surface, or its receptor, setting the mast cell off again and again.
Some people have both. About 27% of patients carry antithyroid antibodies, so doctors often check thyroid markers.
Numbers · How long chronic hives last
How long it lasts varies widely. One review's pooled figures: about half of people get better on their own in around three months, and almost 80% within a year, but more than one in ten can expect it to last 5 years or longer. The international guideline adds that it can come back months or years after clearing up.Because the disease rises and falls, once it is under control a doctor usually reassesses every 3 to 6 months whether treatment is still needed.
A few things make chronic spontaneous urticaria worse: up to a third of patients feel that stress aggravates it; infections can also make it flare; and such as ibuprofen and aspirin make it worse in up to a quarter of patients.
Mechanism · When cold, scratching or heat trigger it
Inducible hives have a definite trigger: they appear whenever the trigger reaches a person's own threshold, and never without it. The most common kind is dermographism: stroke or scratch the skin and it rises along that line; spots where waistbands or sock elastic press are often affected too. Others include cold urticaria, pressure urticaria, heat urticaria, and cholinergic urticaria, set off by a rise in body temperature after exercise or heat.In most inducible hives, symptoms appear within 10 minutes of meeting the trigger and fade within 1 to 3 hours after it is gone.
Avoiding the trigger helps, but the international guideline cautions against shrinking your life to do it: cholinergic urticaria is no reason to stop exercising altogether, and solar urticaria is no reason never to go outdoors.
Chapter 5
What you can do at home
Wheals come from mast cells releasing histamine, so there are two things you can do at home: give mast cells fewer chances to fire, and keep histamine off its receptor.
Find your triggers: note what you ate, what you did and what medicines you took before each outbreak, and photograph the wheals. Common triggers include certain foods, cold, hot sweaty skin (from exercise, emotional stress or spicy food), scratching and pressure (such as tight, itchy clothing), insect bites and infections. Once you find them, avoid them where you can.Watch your painkillers: such as ibuprofen and aspirin make chronic spontaneous urticaria worse in up to a quarter of patients. If you take them often, tell your doctor, who decides whether and what to switch to; if you take aspirin for your heart, do not stop it on your own.Use antihistamines well: a second-generation antihistamine is the first step for every type of hives, and a pharmacist can advise you.
Stress makes hives worse for some people too, and ways to reduce it may help.
Find your triggers: note what you ate, what you did and what medicines you took before each outbreak, and photograph the wheals. Common triggers include certain foods, cold, hot sweaty skin (from exercise, emotional stress or spicy food), scratching and pressure (such as tight, itchy clothing), insect bites and infections. Once you find them, avoid them where you can.Watch your painkillers: such as ibuprofen and aspirin make chronic spontaneous urticaria worse in up to a quarter of patients. If you take them often, tell your doctor, who decides whether and what to switch to; if you take aspirin for your heart, do not stop it on your own.Use antihistamines well: a second-generation antihistamine is the first step for every type of hives, and a pharmacist can advise you.
Stress makes hives worse for some people too, and ways to reduce it may help.
In practice · Antihistamines and steroids
When you ask a pharmacist, mention any long-term conditions, since antihistamines may not suit everyone; ask before giving them to young children as well. The international guideline recommends second-generation antihistamines, which cause little or no drowsiness; the older kind causes sleepiness and impairs driving and is not recommended as the first choice.For chronic hives, the guideline advises taking the antihistamine every day to prevent wheals, rather than only when they appear. If a standard dose does not control them, a doctor may raise the dose beyond the label or move to another treatment; which drug, how much and for how long is for the doctor to decide.
Two common habits miss the mark:
Steroid creams work well in many allergic conditions but do little for hives.Steroid tablets: for acute hives or a sudden flare of chronic hives, a doctor may prescribe a short course of up to about 10 days; long-term use brings heavy side effects, and the guideline strongly recommends against it.
Myth · Should you cut out foods
Many people's first move is to cut out foods. But for chronic spontaneous urticaria, the international guideline concludes that food allergy is rarely the trigger. A Canadian review puts it more bluntly: working through foods with elimination diets does not help.The guideline leaves only a narrow opening. In the few patients who notice that certain foods make things worse, a doctor can arrange a diagnostic diet low in pseudoallergens or histamine, usually for 2 to 3 weeks, to test the idea; it should not delay effective treatment. The guideline also warns that histamine intolerance is often overdiagnosed, leading to needless food restrictions and supplement buying.
Acute hives are different: if a particular food brings on hives every time, it may be a food allergy, which should be confirmed and then strictly avoided; see What sets off acute hives.
Chapter 6
When to get emergency or medical help
Most hives clear up on their own. Don't wait in these situations:
Call emergency services now (120 in mainland China), whether or not there are hives on the skin:
The lips, mouth, tongue or throat suddenly swell.Breathing is very fast or a struggle, or there is wheezing.The throat feels tight, swallowing is hard, or the voice turns hoarse.The skin, lips or tongue turn blue, gray or pale.Sudden confusion, drowsiness, dizziness or fainting.A child is limp and floppy or does not respond.
These are signs of anaphylaxis, a severe allergic reaction. While waiting for the ambulance, use an adrenaline auto-injector at once if a doctor has prescribed one. Lie down and raise your legs, or sit up slowly if you are struggling to breathe. Do not stand up or walk around, even if you feel better.
See a doctor soon if hives have not improved after 2 days, are spreading or keep coming back; if you also have a fever and feel unwell; if there is swelling under the skin; or if you are worried about a child's hives.
Book an appointment if hives keep coming and going for more than 6 weeks.
Call emergency services now (120 in mainland China), whether or not there are hives on the skin:
The lips, mouth, tongue or throat suddenly swell.Breathing is very fast or a struggle, or there is wheezing.The throat feels tight, swallowing is hard, or the voice turns hoarse.The skin, lips or tongue turn blue, gray or pale.Sudden confusion, drowsiness, dizziness or fainting.A child is limp and floppy or does not respond.
These are signs of anaphylaxis, a severe allergic reaction. While waiting for the ambulance, use an adrenaline auto-injector at once if a doctor has prescribed one. Lie down and raise your legs, or sit up slowly if you are struggling to breathe. Do not stand up or walk around, even if you feel better.
See a doctor soon if hives have not improved after 2 days, are spreading or keep coming back; if you also have a fever and feel unwell; if there is swelling under the skin; or if you are worried about a child's hives.
Book an appointment if hives keep coming and going for more than 6 weeks.
Red flag · Why anaphylaxis needs an ambulance
Anaphylaxis runs on the same mechanism as hives, only wider: mast cells and basophils throughout the body suddenly release histamine and other substances together. By the World Allergy Organization's criteria, anaphylaxis is highly likely when, within minutes to hours, the skin or moist linings are involved (hives all over, itching, flushing, or a swollen lip or tongue) together with trouble breathing, a drop in blood pressure, or severe cramping belly pain and repeated vomiting.It can kill, and no one can predict whether it will get worse, so the first-line treatment is adrenaline injected into a muscle; antihistamines help only the skin symptoms. Remember also that 10% to 20% of anaphylaxis reactions show no rash, so no hives does not mean you are safe.
Anyone who has had one should then see an allergy specialist to find the cause and learn how to prevent and handle another.
Red flag · Swelling with no hives and no itch
One kind of swelling looks like hives but works differently: it is not mast cells releasing histamine but mainly another substance, bradykinin, at work, and its tests and treatment are very different from ordinary hives. The clue is swelling alone, with no wheals and no itch.ACE inhibitor blood pressure drugs: think of it if someone on one of these drugs gets swelling without hives. Most cases start in the first week on the drug, but up to a third come months or even years later.Hereditary angioedema: swelling that keeps coming back, with no wheals and no itch.
Once this kind of swelling reaches the throat, it can be fatal. So with throat or tongue swelling or trouble breathing, call emergency services now just the same; and if you have ever had swelling without hives while taking an ACE inhibitor, tell your doctor soon, who will decide whether to change the drug.
References · 6
- Zuberbier, T., Ansari, Z. A., Abdul Latiff, A. H., Abuzakouk, M. M., Agcaoili-De Jesus, M. S., et al. (2026). The international guideline for the definition, classification, diagnosis and management of urticaria. Allergy, 81(8), 2582-2632. GA2LEN-led GRADE guideline, consensus conference 6 December 2024. Urticaria is a frequent, mast cell-driven disease defined by a rapid appearance of wheals, angioedema or both; the lifetime prevalence of acute urticaria is estimated to be approximately 20%. A wheal: a sharply circumscribed superficial central swelling almost invariably surrounded by reflex erythema, an itching or sometimes burning sensation, and a fleeting nature, the skin returning to normal usually within 30 min to 24 h. Angioedema: a sudden deep swelling in the lower dermis and subcutis or mucous membranes, with tingling, burning, tightness and sometimes pain rather than itch, resolving more slowly (can take up to 72 h). Acute urticaria lasts 6 weeks or less, chronic more than 6 weeks; spontaneous (no definite eliciting factor) or inducible (a definite subtype-specific trigger such as cold); in most inducible urticarias symptoms appear within 10 min of exposure and resolve within 1-3 h after it stops; CSU episodes may recur after months or years of full remission. Mast cell activation releases mediators such as histamine and platelet-activating factor, responsible for sensory nerve stimulation (pruritus), vasodilatation (erythema) and inflammatory cell chemoattraction; wheals show degranulated mast cells with oedema of the upper and mid dermis and dilated, more permeable postcapillary venules; in angioedema similar changes occur primarily in the lower dermis. Besides the histamine receptor, other mast cell receptors such as MRGPRX2 are involved. In more than 50% of CSU patients the pathophysiology is driven by two autoimmune mechanisms: type I (autoallergy, IgE autoantibodies against autoallergens) and type IIb (mast cell-activating IgG autoantibodies); some patients have both. Acute urticaria frequently follows upper airway infections, including COVID-19, and some cases evolve into CSU. Acute urticaria, being self-limiting, needs no workup beyond a history (recommendation against routine diagnostic measures), except suspected food allergy or drug hypersensitivity, especially to NSAIDs. Drugs cause urticarial reactions via IgE (e.g., penicillin) or non-IgE mechanisms (e.g., NSAIDs); NSAIDs aggravate pre-existing CSU in up to one-fourth of patients, with paracetamol and COX-2 inhibitors considered safer options. Food allergy is rarely a trigger of CSU; diagnostic pseudoallergen- or histamine-low diets may be considered only in selected patients, usually for 2-3 weeks, and should not delay effective treatment; overdiagnosis of histamine intolerance should be avoided. Some CSU patients experience trigger-induced augmentation of wheals or angioedema, among others by stress and infections; up to one-third of CSU patients perceive stress as an aggravating factor. Because severity fluctuates and spontaneous remission may occur at any time, the need for continued drug treatment should be re-evaluated every three to 6 months. Trigger avoidance should be balanced with quality of life (not, for example, stopping all exercise). Strong recommendation: a standard-dosed modern second-generation H1-antihistamine as first-line treatment for all types of urticaria, taken daily rather than on demand in chronic urticaria; H1-antihistamines act as inverse agonists that stabilise the inactive state of the H1 receptor; modern second-generation H1-antihistamines are minimally or nonsedating; recommends against first-generation H1-antihistamines as first-line (sedation, impaired driving, lethal overdoses reported); updosing is off-label. Topical corticosteroids, frequently and successfully used in many allergic diseases, are not useful in urticaria; strongly recommends against prolonged systemic corticosteroids, while a short course of up to 10 days may help in acute urticaria or exacerbations. Anaphylaxis, urticarial vasculitis and bradykinin-mediated angioedema (e.g., with ACE inhibitors, hereditary angioedema) must be distinguished from urticaria (full text PMC13466004; PMID 41649409). 10.1111/all.70210
- Kanani, A., Betschel, S. D., & Warrington, R. (2018). Urticaria and angioedema. Allergy, Asthma & Clinical Immunology, 14(Suppl 2), 59. Urticaria occurs in 15-25% of people at some point in life; lesions are often transient, resolving within about 24 h without scarring, though some last up to 48 h; about 40% of patients with urticaria also have angioedema. Mast cells, widely distributed in the skin and mucosa, carry high-affinity IgE receptors; their degranulation rapidly releases histamine, leukotrienes and prostaglandins, which cause vasodilation and leakage of plasma in and below the skin, followed by a delayed (4-8 h) secretion of inflammatory cytokines that potentially leads to further inflammation and longer-lasting lesions. Chronic urticaria prevalence is estimated at 0.5-5%, peak onset at 20-40 years, more common in women; in CSU an external trigger usually cannot be identified; in about 45% IgG autoantibodies recognise IgE or the alpha subunit of the high-affinity IgE receptor on mast cells and basophils; antithyroid antibodies in about 27%. The most common causes of acute urticaria are medications, foods, viral infections, stress, parasitic infections, insect venom and contact allergens; the predominant foods are milk, eggs, peanuts, tree nuts, fish and shellfish; in about 50% of acute urticaria the cause is unknown (acute spontaneous urticaria), and up to 36% of these progress to CSU. Dermatographism is the most common physical urticaria (stroking or scratching; tight waistbands and sock elastic); cholinergic urticaria follows a rise in body temperature with exertion or heat. In CSU, NSAIDs, alcohol and opiates should be avoided as they can significantly exacerbate it; food avoidance with elimination diets is not helpful for CSU. Second-generation non-sedating H1-antihistamines are the mainstay of therapy; first-generation antihistamines should be avoided (sedation, cognitive impairment). Hereditary and acquired angioedema present as angioedema without urticaria or itch, and ACE inhibitor angioedema should be suspected in anyone on an ACE inhibitor who develops angioedema without urticaria; bradykinin-mediated angioedema with laryngeal involvement can lead to fatal asphyxiation; up to one-third of ACE inhibitor angioedema occurs months to years after starting the drug (full text PMC6157046; PMID 30263036). 10.1186/s13223-018-0288-z
- NHS. (2024). Hives (page last reviewed 26 April 2024). Hives rashes usually get better within a few days; the main symptom is an itchy rash of raised bumps or patches that can sting or burn, and its colour can be harder to see on brown and black skin. A pharmacist can advise on antihistamines; tell them about any long-term condition; this may not suit young children. Ask for an urgent GP appointment or NHS 111 if hives do not improve after 2 days, you are worried about a child's hives, the rash is spreading, hives keep coming back, you also have a high temperature and feel unwell, or there is swelling under the skin (angioedema). Call 999 if the lips, mouth, throat or tongue suddenly swell, breathing is very fast or a struggle, the throat feels tight or swallowing is hard, skin, tongue or lips turn blue, grey or pale, you suddenly become very confused, drowsy or dizzy, someone faints and cannot be woken, or a child is limp or floppy. Hives occur when a trigger causes high levels of histamine and other chemicals to be released in the skin; triggers include certain foods, contact with plants, animals, chemicals or latex, cold, hot sweaty skin from exercise, emotional stress or spicy food, a medicine, insect bite or sting, scratching or pressing on the skin such as itchy or tight clothing, an infection, an immune system problem, and rarely water or sunlight; finding and avoiding your triggers may help prevent episodes. A GP might prescribe menthol cream, antihistamines or steroid tablets. www.nhs.uk/conditions/hives
- Cardona, V., Ansotegui, I. J., Ebisawa, M., El-Gamal, Y., Fernandez Rivas, M., Fineman, S., Geller, M., Gonzalez-Estrada, A., Greenberger, P. A., Sanchez Borges, M., Senna, G., Sheikh, A., Tanno, L. K., Thong, B. Y., Turner, P. J., & Worm, M. (2020). World Allergy Organization anaphylaxis guidance 2020. World Allergy Organization Journal, 13(10), 100472. Anaphylaxis is a serious systemic hypersensitivity reaction, usually rapid in onset, that may cause death; it results from the sudden release of mediators from mast cells and basophils. It is highly likely when an acute illness (minutes to several hours) involves the skin or mucosa (generalized hives, itch or flushing, swollen lips-tongue-uvula) together with respiratory compromise, reduced blood pressure or end-organ dysfunction, or severe gastrointestinal symptoms (e.g., severe crampy abdominal pain, repetitive vomiting); or with acute hypotension, bronchospasm or laryngeal involvement after exposure to a known allergen even without skin signs. Skin signs are absent in 10-20% of reactions. Cofactors include exercise, infections, alcohol and medications. Most reactions are not life-threatening in themselves, but because progression cannot be predicted all anaphylaxis must be treated with intramuscular adrenaline (epinephrine), the first-line treatment; H1-antihistamines have a limited role and can help only cutaneous symptoms; after anaphylaxis patients should be referred to a specialist to assess the cause and be educated on prevention of recurrences and self-management (full text PMC7607509; PMID 33204386). 10.1016/j.waojou.2020.100472
- Sánchez-Borges, M., Ansotegui, I. J., Baiardini, I., Bernstein, J., Canonica, G. W., Ebisawa, M., Gomez, M., Gonzalez-Diaz, S. N., Martin, B., Morais-Almeida, M., & Ortega Martell, J. A. (2021). The challenges of chronic urticaria part 1: Epidemiology, immunopathogenesis, comorbidities, quality of life, and management. World Allergy Organization Journal, 14(6), 100533. Point prevalence of chronic urticaria, from health-system coding in different countries, ranges from 0.1 to less than 1% globally; one-third of patients have both hives and angioedema, 30-40% hives alone and around 10% angioedema alone. The natural history varies widely: around half of patients follow a three-month self-limited course and within a year it resolves in almost 80%, but in more than 10% a duration of 5 years or longer is expected. Females are affected at least twice as often as males, and most patients are over 20. Mechanisms include IgG autoantibodies to FcεRI or IgE on mast cells and basophils (autoimmunity type II) and IgE autoantibodies to self-antigens such as thyroid peroxidase, DNA and IL-24 (autoimmunity type I, autoallergy); histamine, PAF, tryptase, leukotrienes and cytokines from activated skin mast cells cause sensory nerve activation, vasodilatation and plasma extravasation (full text PMC8233382; PMID 34221215). 10.1016/j.waojou.2021.100533
- NHS. (2023). Anaphylaxis (page last reviewed 21 June 2023). A life-threatening allergic reaction that happens very quickly, usually within minutes of contact with something you are allergic to, such as a food, medicine or insect sting. Symptoms include swelling of the throat and tongue, difficulty breathing or breathing very fast, difficulty swallowing, tightness in the throat or a hoarse voice, wheezing, feeling faint, dizzy or fainting, and blue, grey or pale skin, lips or tongue; there may also be a swollen, raised or itchy rash. Call 999. Use an adrenaline auto-injector if you have one; lie down and raise the legs, or sit up slowly if struggling to breathe; use a second auto-injector if symptoms have not improved after 5 minutes; do not stand or walk at any time, even if you feel better. Anaphylaxis needs immediate treatment in hospital, usually a stay of around 2 to 12 hours. www.nhs.uk/conditions/anaphylaxis