Antihistamines and itch

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Meet the patient

A 34-year-old woman arrives at 3am with an itchy rash of migratory wheals that has troubled her trunk for ten weeks — well past the six-week line that separates chronic urticaria from acute. Chronic spontaneous urticaria impairs quality of life: approximately 40 percent of patients have a Dermatology Life Quality Index of more than 10, corresponding to a very large or extremely large negative effect. Partial or complete response to a standard-dose second-generation H1 antihistamine — a greater than 50 percent reduction in urticaria symptoms — is observed in approximately 40 percent of patients.^[1][2]

The two questions that decide her next three months are the two every urticaria stem turns on: is this histamine-driven? (the migrating wheals say yes) and how far up the ladder do I climb before I call it refractory? Hold those two and the whole topic lines up.^[1]

One receptor, two generations

Oral H1-antihistamines are the most commonly used therapy for allergic rhinitis and chronic urticaria (CSACI). In this topic the dermatology-relevant family is the H1 antihistamines, first-line for urticaria and allergic rhinitis. Urticaria is a mast-cell-driven disease presenting with wheals or angioedema or both.^[7][3]

H1-receptors are G-protein-coupled receptors whose inactive and active conformations coexist in equilibrium; the degree of receptor activation in the absence of histamine is its constitutive activity. Histamine acts as an agonist by stabilising the activated conformation. Drugs previously classified as antagonists act as either inverse agonists or neutral antagonists.^[8]

The phrase that earns the mark is "inverse agonist at the H1 receptor," not "competitive antagonist." Inverse agonists combine with and stabilise the inactive conformation of the receptor to shift the equilibrium towards the inactive state, and they may down-regulate constitutive receptor activity even in the absence of histamine.^[8]

Histamine acts on more than one receptor subtype, but in urticaria the lens stays on two. H1 signalling drives the wheal and the itch — histamine released from skin mast cells is the defining mediator of the disease; H2 is the supporting target, where adding an H2-receptor antagonist to an H1 agent improved outcomes over the H1 agent alone in the small pooled trials (evidence and caveats below).^[2][14]

Two generations — the split that runs the whole topic

First-generation agents have significant and common side effects; second-generation agents are the recommended first-line treatment. CSACI: older first-generation H1-antihistamines (for example diphenhydramine, hydroxyzine) cause sedation, decreased cognitive function, poor sleep quality, dry mouth, dizziness, and orthostatic hypotension, and have been found to result in death from accidents, overdoses, and sudden cardiac death. They should be used only as a last resort. Newer-generation agents are first-line for allergic rhinitis and urticaria.^[7]

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The classic trap is defaulting to a first-generation agent. CSACI: they have significant and common side effects and should be used only as a last resort; newer-generation agents are first-line. Pelen: antihistamines are among the most common anticholinergic classes in community-dwelling older adults.^[7][18]

Usual therapeutic doses that appear in the sleepiness network meta-analysis

Licensed milligram schedules, half-lives, and onset times are not reproduced from product labels in this pass. What the fetched papers do state:^[11]

Wang: bilastine can be used at up to fourfold the standard dosage (80 mg once daily) in urticaria, with no cardiotoxicity and less sedative potential than other second-generation agents in that review. Torres-Betato: up-dosing second-generation antihistamines up to four times the standard dose can enhance symptom control without compromising tolerability, with an excellent cardiovascular safety profile, and these agents are generally safe in paediatric, elderly, and renally or hepatically impaired patients, with appropriate caution during pregnancy and lactation. Wang: bilastine is not metabolised and is excreted largely unchanged, so hepatic impairment is not expected to increase systemic exposure above its safety margin, and it does not require dose adjustment in renal impairment.^[11][12][10]

First-generation examples named by CSACI are diphenhydramine and hydroxyzine. Specific milligram TDS/QDS schedules for chlorpheniramine, promethazine, and hydroxyzine are not in the fetched abstracts and are omitted here.^[7]

H2 blockers, interactions, and the ranitidine ghost

H2 receptors are a real second target in urticaria. A Cochrane review found that adding an H2-receptor antagonist to an H1 agent improved resolution of urticaria — ranitidine plus diphenhydramine beat diphenhydramine alone (RR 1.59), and cimetidine plus diphenhydramine beat diphenhydramine alone (RR 2.02) — although the reviewers judged the evidence weak and unreliable. In a small double-blind emergency-department trial, famotidine 20 mg intramuscularly reduced pruritus, urticaria intensity, and affected body-surface area in acute urticaria without causing sedation.^[14][15]

Wang: bilastine does not interact with the cytochrome P450 system and does not require dose adjustment in renal impairment. Torres-Betato: second-generation agents have an excellent cardiovascular safety profile. Leurs: blockade of HERG1 K+ channels is the arrhythmia mechanism for some H1-antihistamines. Unsourced food, antacid, and GFR-cutoff rules are omitted here.^[8][10][12]

First-generation agents add a second layer of trouble. CSACI lists sedation, decreased cognitive function, dry mouth, dizziness, and orthostatic hypotension; Pelen found antihistamines among the most common anticholinergic medication classes in community-dwelling older adults. The AGS Beers Criteria are an explicit list of potentially inappropriate medications typically best avoided by older adults — the 2019 abstract does not itself name first-generation antihistamines.^[7][18][6]

The drugs that are not H1 antihistamines but get mistaken for them

Not every anti-itch or anti-urticaria drug is an H1 antihistamine. Gülen: in non-advanced systemic mastocytosis, traditional symptom-directed therapy includes antihistamines, leukotriene modifiers, and mast-cell stabilisers. Alkeraye: montelukast is an add-on in histamine-resistant chronic idiopathic urticaria (small series). Butler: doxepin is listed among antidepressants used for neuropathic chronic pruritus. Omalizumab is the 2022-guideline second-line treatment for antihistamine-refractory CSU.^{[20][19][13][1]}

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How common, who, and what sets it off

Histamine-mediated itch is everywhere. Urticaria affects up to 20 percent of the world population at some point during their life. Most cases are acute, lasting six weeks or less; chronic urticaria lasts more than six weeks and persists for more than a year in most patients. Chronic spontaneous urticaria affects approximately 1 percent of the general population and is most common in females aged 30 to 50 years.^[2][1]

Acute urticaria can be associated with infections or intake of drugs or foods. Chronic inducible urticaria has definite and subtype-specific triggers (for example cold or pressure). Known autoimmune CSU endotypes are mediated by mast-cell-activating IgE and/or IgG autoantibodies (more than 50 percent).^[2][5][1]

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Why histamine does what it does — and why the drug sometimes cannot

Urticaria presents with wheals, angioedema, or both due to activation and degranulation of skin mast cells and the release of histamine and other mediators. The pathogenesis of CSU involves autoantibodies, complement, and coagulation. Inverse agonists combine with and stabilise the inactive H1-receptor conformation and may down-regulate constitutive activity even in the absence of histamine.^[2][8]

Why first-generation sedates and second-generation does not

Sedation ranking among newer agents is empirical, not a P-glycoprotein lecture. Leelakanok's network meta-analysis found the least-sedating antihistamine in adults was bilastine 20 mg (sleepiness prevalence 1.6%); at usual therapeutic doses, bepotastine 20 mg, bilastine 20 mg, desloratadine 5 mg, and fexofenadine 120 to 180 mg had sleepiness prevalence under 10% and not significantly different from placebo. CSACI: first-generation agents cause marked sedation and cognitive impairment. Unsourced P-glycoprotein and zwitterion mechanics are omitted.^[11][7]

The hERG story — the arrhythmia mechanism

Blockade of HERG1 K+ channels is the mechanism by which some H1-antihistamines may cause cardiac arrhythmias — that is the Leurs finding that allowed preclinical tests to predict such activity. Torres-Betato: currently used second-generation agents demonstrate an excellent cardiovascular safety profile. Wang: bilastine has no cardiotoxicity. Unsourced CYP3A4–macrolide recipes are omitted here (not in the fetched abstracts).^[8][10][12]

Why antihistamines fail in atopic, cholestatic, and uraemic itch

If histamine is not the mediator, an H1 blocker is the wrong tool. Frazier: oral antihistamines are not recommended in atopic dermatitis because they do not reduce pruritus. Butler: about 15 percent of chronic pruritus has other causes including systemic diseases with secondary itch such as uraemic pruritus and cholestatic pruritus; neuropathic or mixed etiology is about 25 percent.^[4][13]

The clinical picture — and the mimics that bite

Urticaria presents with wheals, angioedema, or both. Chronic inducible urticaria has definite and subtype-specific triggers (for example cold or pressure). Torres-Betato: second-generation agents are generally safe in paediatric, elderly, and organ-impaired patients, with appropriate caution during pregnancy and lactation. CSACI: first-generation agents cause dry mouth, dizziness, orthostatic hypotension, and decreased cognitive function — last resort, especially relevant in older adults (Pelen).^{[2][5][10][7][18]}

Match the mediator to the drug class. Atopic dermatitis: oral antihistamines do not reduce pruritus. Butler: inflammatory chronic pruritus (~60 percent) versus neuropathic/mixed (~25 percent) versus other systemic causes including uraemic and cholestatic pruritus (~15 percent).^[4][13]

The differential — and the angioedema fork that must not be missed

Urticaria is a mast-cell-driven disease presenting with wheals or angioedema or both. If the swelling comes without the urticarial signature, do not assume an H1 antihistamine will work — named non-histamine angioedema drugs are not in the fetched abstracts. EAACI: when this is anaphylaxis, prompt intramuscular adrenaline is first-line.^[3][16]

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Chronic urticaria is either spontaneous or inducible, lasts more than six weeks, and persists for more than a year in most patients. CIndU has definite and subtype-specific triggers; CSU does not. Diagnosis is clinical, but tests can be performed to exclude differential diagnoses and identify underlying causes or triggers. Non-advanced systemic mastocytosis is a clonal mast-cell disorder with pruritus, flushing, gastrointestinal symptoms, and anaphylaxis — not ordinary CSU.^[2][20]

At the bedside — history, provocation, and the photo tip

Take onset, whether lesions are wheals, angioedema, or both, and whether a definite trigger exists (that fork is CSU versus CIndU). Acute urticaria can be associated with infections or intake of drugs or foods. Autoimmune CSU endotypes are mediated by IgE and/or IgG autoantibodies in more than 50 percent.^[2][1]

Investigations — usually none, sometimes two

Diagnosis of CSU is clinical — spontaneously recurring wheals, angioedema, or both. The primer: several tests can be performed to exclude differential diagnoses and identify underlying causes in CSU or triggers in CIndU. EAACI anaphylaxis guideline suggests using clinical criteria to identify anaphylaxis, with blood sampling for later tryptase measurement. Unsourced C4 panels, a 20 ng/mL tryptase cut-off, and named biopsy-histology recipes are omitted.^[1][2][16]

Anaphylaxis — the place antihistamines must never be first-line

Adrenaline is the drug; antihistamines are the garnish. For chronic urticaria itself, non-sedating antihistamines are the recommended medical therapy — but the moment urticaria or angioedema comes with airway compromise, this is anaphylaxis, and the guideline recommendation is prompt intramuscular adrenaline as first-line management, undelayed.^[3][16]

Adrenaline, intramuscularly, without delay — the guideline position. The EAACI anaphylaxis guideline recommends the prompt use of intramuscular adrenaline as first-line management, with adrenaline autoinjectors made available to patients at risk in the community. An American Academy of Pediatrics clinical report adds that prompt intramuscular injection into the mid-outer thigh reduces hospitalisations, morbidity, and mortality, and that prescribing autoinjectors facilitates timely injection in community settings.^[16][17]

Antihistamines relieve the skin but reverse nothing that kills. The guideline's first-line recommendation is prompt intramuscular adrenaline — antihistamines are not the resuscitation drug for anaphylaxis. Structured, comprehensive training for people at risk is recommended, and simulation training with visual prompts is suggested for healthcare professionals to improve anaphylaxis management.^[16]

The CSU ladder — four-fold, then omalizumab

The mantra: standard dose, then four-fold the approved dose, then omalizumab, then ciclosporin. Current management guidelines recommend that sequence. Kolkhir JAMA: second-generation H1 antihistamines first-line, omalizumab second-line, cyclosporine third-line. The recurring trainee error is to stop at standard dose and label the patient refractory.^[1][5]

Step 1 — standard-dose second-generation agent. Usual therapeutic doses in Leelakanok include bilastine 20 mg, desloratadine 5 mg, and fexofenadine 120 to 180 mg. Partial or complete response at standard dose (greater than 50 percent reduction in urticaria symptoms) is observed in approximately 40 percent of patients. ^[11][1]

Step 2 — up-titrate the same agent. International management guidelines recommend step-up administration of second-generation H1-antihistamines to four-fold the approved dose when standard dosing fails. ^[5]

Step 3 — the ceiling is fourfold, and it is tolerated. Torres-Betato: up-dosing to four times the standard dose enhances symptom control without compromising tolerability. Wang: bilastine can be used at up to fourfold the standard dosage (80 mg once daily). Second-generation agents carry an excellent cardiovascular safety profile. ^[10][12]

Step 4 — add omalizumab. The 2022 international urticaria guideline recommends omalizumab as second-line treatment for antihistamine-refractory CSU. Saini (n=90): a single subcutaneous dose of 300 mg (UAS7 −19.9 vs −6.9 placebo) or 600 mg (−14.6 vs −6.9) improved scores, with onset after 1 to 2 weeks; 75 mg showed no meaningful difference from placebo. At least 30 percent of patients have an insufficient response to omalizumab. ^[1][9]

Step 5 — add ciclosporin. Cyclosporine, used off-label, improves symptoms in approximately 54 to 73 percent of patients — especially autoimmune CSU and omalizumab non-responders — at the cost of adverse effects such as kidney dysfunction and hypertension. ^[1]

Adjuncts and alternative agents

H2 blocker. A Cochrane review found adding an H2-receptor antagonist to an H1 agent improved urticaria outcomes — ranitidine plus diphenhydramine (RR 1.59) and cimetidine plus diphenhydramine (RR 2.02) both beat the H1 agent alone — though the evidence was judged weak and unreliable. ^[14]

Leukotriene antagonist. Leukotriene receptor antagonists such as montelukast are effective as add-on therapy to antihistamines in chronic idiopathic urticaria, and their use in histamine-resistant patients is justifiable, per a small clinical series. ^[19]

Doxepin. Antidepressants such as doxepin are listed among the effective systemic therapies for neuropathic chronic pruritus, alongside gabapentin, sertraline, and opioid receptor agonist/antagonists such as naltrexone or butorphanol. ^[13]

The prescribing checklist that keeps you out of trouble

Confirm the presentation is urticaria (wheals, angioedema, or both) before you treat it as histamine-driven. Pick a newer-generation agent. In CSU, start at standard dose and climb to four-fold the approved dose before you write "refractory," then omalizumab. Keep first-generation agents as a last resort — CSACI lists accidents among the reported deaths. Pelen: antihistamines are a common anticholinergic class in older adults. Wang: bilastine does not require renal-impairment dose adjustment.^{[1][5][7][18][12]}

Special situations — mastocytosis, physical urticarias, the itches that are not histamine

Mastocytosis. In non-advanced systemic mastocytosis, mediator-related symptoms — pruritus, flushing, gastrointestinal symptoms, anaphylaxis — are the major source of morbidity and substantially impair quality of life; traditional symptom-directed therapy with antihistamines, leukotriene modifiers, and mast-cell stabilisers remains the foundation of care, with selective KIT inhibitors and other targeted agents emerging for refractory symptoms. ^[20]

Chronic inducible urticaria has definite and subtype-specific triggers (for example cold or pressure) in Zuberbier's classification. The same four-fold second-generation H1 step-up is the guideline pathway for chronic urticaria generally. Unsourced swimming, desensitisation, and ADGRE2 claims are omitted.^[5][2]

Atopic dermatitis is not primarily a histamine-driven itch: oral antihistamines are not recommended because they do not reduce pruritus. First-line for flares is topical corticosteroids, with topical calcineurin inhibitors (pimecrolimus, tacrolimus) usable alongside as first-line therapy; phototherapy is safe and effective when first-line treatment is inadequate; the newer FDA-approved agents crisaborole and dupilumab treat refractory disease. Maintenance is emollients plus soap-free bathing. ^[4]

Allergic rhinitis and urticaria share the same CSACI first-line: newer-generation H1-antihistamines. First-generation agents are last resort. If the episode is anaphylaxis, EAACI: prompt intramuscular adrenaline first-line.^[7][16]

Non-histaminergic systemic itch is where antihistamines disappoint. Butler: chronic pruritus is inflammatory in approximately 60 percent (eczema, psoriasis, or seborrheic dermatitis) and neuropathic or mixed in approximately 25 percent (including postherpetic neuralgia); first-line inflammatory therapy is topical anti-inflammatory treatment such as hydrocortisone 2.5 percent, triamcinolone 0.1 percent, or tacrolimus ointment; approximately 10 percent do not respond to topicals. Other effective therapies for neuropathic pruritus include gabapentin, antidepressants such as sertraline or doxepin, or opioid receptor agonist/antagonists such as naltrexone or butorphanol.^[13]

Pitfalls — the anticholinergic elderly, the un-escalated CSU, the first-generation default

Anticholinergic burden in older adults is the headline harm. Antihistamines are among the most common anticholinergic medication classes used by community-dwelling older adults, and greater anticholinergic burden is associated with physical and cognitive impairment. First-generation agents add sedation, decreased cognitive function, poor sleep quality, dry mouth, dizziness, and orthostatic hypotension — with deaths reported from accidents, overdoses, and sudden cardiac death — and they are recommended only as a last resort; the AGS Beers Criteria are the explicit reference list of potentially inappropriate medications typically best avoided by older adults. Choose a second-generation agent, always.^[18][7][6]

Cardiac arrhythmia from some H1-antihistamines is a HERG1 K+ channel effect (Leurs). Torres-Betato: currently used second-generation agents have an excellent cardiovascular safety profile. CSACI: first-generation agents have been found to result in sudden cardiac death.^[8][10][7]

CSACI: first-generation antihistamines continue to be over-utilised because of over-the-counter status and long history of use; they should be used only as a last resort. Unsourced FDA-under-2, topical type-IV, and milligram-overdose recipes are omitted.^[7]

Failure to escalate is the commonest chronic-care error. Patients sit on sub-therapeutic doses for months. Climb to four times before you call it refractory, and refer for omalizumab rather than stacking low-value drugs.^[1]

Prognosis — relapsing, remitting, and surprisingly disabling

CSU persists for more than 1 year in most patients (one or repeated episodes) and is most common in females aged 30 to 50 years. Standard-dose second-generation H1 antihistamines produce a partial or complete response in approximately 40 percent. At least 30 percent of patients have an insufficient response to omalizumab. Unsourced median-duration, one-year-remission, and “two-thirds rescued” figures are omitted.^[1]

Most patients are outpatients. Refer urgently for anaphylaxis, airway-threatening angioedema, or suspected mastocytosis or hereditary angioedema. Refer to allergy or dermatology when four-times dosing has failed and omalizumab is on the table. Systemic mastocytosis needs lifelong follow-up, trigger counselling, and an auto-injector. Reassure the CSU patient that the disease is rarely life-threatening — but emergency care is mandatory for tongue or throat swelling, breathing difficulty, dizziness, or syncope.^[1]

Driving, occupation, and the medicolegal line

Sedation and accidents are the occupational hazard of first-generation agents. CSACI: they cause sedation and decreased cognitive function and have been found to result in death from accidents; use only as a last resort. Leelakanok: even newer-generation agents at usual doses have a higher sleepiness prevalence than placebo, though most differences are not statistically significant; bilastine 20 mg was the least-sedating in adults.^[7][11]

CSACI recommends that newer-generation H1-antihistamines should be preferred, and first-generation agents used only as a last resort — including because of accidents. Pelen: antihistamines are among the most common anticholinergic classes in community-dwelling older adults. Document the rationale and the intended duration.^[7][18]

Special populations — pregnancy, age, organ failure, the immunocompromised

Pregnancy and breastfeeding. Torres-Betato: second-generation antihistamines are generally safe in paediatric, elderly, and renally or hepatically impaired patients, with appropriate caution during pregnancy and lactation. Ranked “safest in pregnancy” claims (loratadine vs cetirizine vs fexofenadine) are not in the fetched abstracts and are omitted.^[10]

Older adults. Antihistamines are among the most common anticholinergic medication classes in community-dwelling older adults, and greater anticholinergic burden is associated with physical and cognitive impairment — so prefer newer-generation agents; first-generation antihistamines should be used only as a last resort. The AGS Beers Criteria are the explicit reference list of potentially inappropriate medications typically best avoided by older adults. ^[18][7][6]

Children. Second-generation agents are preferred in children: high-quality trials have proven newer-generation H1 antihistamines superior in safety to first-generation ones, and a comprehensive review finds second-generation agents generally safe in paediatric patients, as in elderly and renally or hepatically impaired patients. ^[7][10]

Hepatic impairment. Bilastine does not undergo significant metabolism and is excreted largely unchanged, so hepatic impairment is not expected to increase systemic exposure above its safety margin; second-generation agents generally are safe in hepatically impaired patients. ^[12][10]

Renal impairment. Bilastine does not require dose adjustment in renal impairment, and second-generation antihistamines as a class are generally safe in renally impaired patients — one more reason they displace the sedating, anticholinergic first-generation agents, which are recommended only as a last resort. ^[12][10][7]

Immunocompromised. Widen the differential to urticarial vasculitis in lupus, cryoglobulinaemia, chronic graft-versus-host disease, and cutaneous lymphoma. Standard antihistamines apply, but the underlying disease usually needs specific therapy; drug-induced urticaria is common in patients buried under antibiotics, anticonvulsants, and biologics — review the list.^[2]

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Evidence, guidelines, and where regions differ

Current management guidelines (Zuberbier 2024, citing the international pathway) recommend step-up administration of second-generation H1-antihistamines to four-fold the approved dose, followed by omalizumab and ciclosporin. Named EuroGuiDerm/APAAACI 2017-replacement language is not in the fetched abstract.^[5]

The development programme that won omalizumab its licence was randomised, placebo-controlled, and dose-ranging: in H1-antihistamine-refractory chronic idiopathic urticaria, fixed subcutaneous doses of 300 mg and 600 mg improved urticaria activity scores rapidly — onset within 1 to 2 weeks — while 75 mg showed no meaningful benefit. Emerging targeted treatment options in clinical trials include Bruton's tyrosine kinase inhibitors, anti-cytokine therapies, and mast-cell depletion. ^[9][5]

Exam pearls

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Ward-round test

A 28-year-old with CSU is still whealing on a standard-dose second-generation antihistamine. What is the next step?ShowHide

Up-titrate to fourfold the approved dose before labelling refractory — guidelines recommend step-up administration to four-fold the approved dose, and up-dosing to four times the standard dose enhances symptom control without compromising tolerability. Only after antihistamine failure at up-dosed levels does omalizumab — fixed 300 mg subcutaneous dosing proven in randomised trials — enter the algorithm. The recurring trainee error is to stop at standard dose and refer prematurely.

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A 78-year-old is prescribed a first-generation antihistamine for itch and falls at night. Why?ShowHide

Anticholinergic and sedative burden. CSACI: first-generation agents cause sedation, decreased cognitive function, dry mouth, dizziness, and orthostatic hypotension and should be used only as a last resort. Pelen: antihistamines are among the most common anticholinergic classes in community-dwelling older adults. Switch to a newer-generation agent (usual doses in Leelakanok include bilastine 20 mg, desloratadine 5 mg, fexofenadine 120 to 180 mg). Wang: bilastine does not require dose adjustment in renal impairment. The 2019 Beers abstract is a PIM list typically best avoided — it does not itself name first-generation antihistamines.

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What is the mechanism by which some H1 antihistamines cause cardiac arrhythmias?ShowHide

Blockade of HERG1 K+ channels (Leurs). Torres-Betato: currently used second-generation agents have an excellent cardiovascular safety profile; Wang: bilastine has no cardiotoxicity.

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A patient has isolated facial swelling without wheals. Why might antihistamines fail?ShowHide

Urticaria is mast-cell-driven wheals or angioedema or both. Isolated swelling without the urticarial signature is not a proven H1-responsive syndrome in the fetched abstracts; do not stack antihistamines. If this is anaphylaxis, EAACI: prompt intramuscular adrenaline first.

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References20ShowHide

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2. [2]Kolkhir P, Giménez-Arnau AM, Kulthanan K, et al. Urticaria Nat Rev Dis Primers, 2022.PMID 36109590
3. [3]Radonjic-Hoesli S, Hofmeier KS, Micaletto S, et al. Urticaria and Angioedema: an Update on Classification and Pathogenesis Clin Rev Allergy Immunol, 2018.PMID 28748365
4. [4]Frazier W, Bhardwaj N. Atopic Dermatitis: Diagnosis and Treatment Am Fam Physician, 2020.PMID 32412211
5. [5]Zuberbier T, Ensina LF, Giménez-Arnau A, et al. Chronic urticaria: unmet needs, emerging drugs, and new perspectives on personalised treatment Lancet, 2024.PMID 39004090
6. [6]By the 2019 American Geriatrics Society Beers Criteria Update Expert Panel. American Geriatrics Society 2019 Updated AGS Beers Criteria® for Potentially Inappropriate Medication Use in Older Adults J Am Geriatr Soc, 2019.PMID 30693946
7. [7]Fein MN, Fischer DA, O'Keefe AW, et al. CSACI position statement: Newer generation H1-antihistamines are safer than first-generation H1-antihistamines and should be the first-line antihistamines for the treatment of allergic rhinitis and urticaria Allergy Asthma Clin Immunol, 2019.PMID 31582993
8. [8]Leurs R, Church MK, Taglialatela M. H1-antihistamines: inverse agonism, anti-inflammatory actions and cardiac effects Clin Exp Allergy, 2002.PMID 11972592
9. [9]Saini S, Rosen KE, Hsieh HJ, et al. A randomized, placebo-controlled, dose-ranging study of single-dose omalizumab in patients with H1-antihistamine-refractory chronic idiopathic urticaria J Allergy Clin Immunol, 2011.PMID 21762974
10. [10]Torres-Betato F, Arnau AMG, Spertino J. Efficacy, safety, and clinical use of second-generation antihistamines for chronic spontaneous urticaria: a comprehensive review Eur J Dermatol, 2026.PMID 42507398
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13. [13]Butler DC, Berger T, Elmariah S, et al. Chronic Pruritus: A Review JAMA, 2024.PMID 38809527
14. [14]Fedorowicz Z, van Zuuren EJ, Hu N. Histamine H2-receptor antagonists for urticaria Cochrane Database Syst Rev, 2012.PMID 22419335
15. [15]Watson NT, Weiss EL, Harter PM. Famotidine in the treatment of acute urticaria Clin Exp Dermatol, 2000.PMID 10844490
16. [16]Muraro A, Worm M, Alviani C, et al. EAACI guidelines: Anaphylaxis (2021 update) Allergy, 2022.PMID 34343358
17. [17]Sicherer SH, Simons FER. Epinephrine for First-aid Management of Anaphylaxis Pediatrics, 2017.PMID 28193791
18. [18]Pelen K, Hagenimana WB, Baroud ML, et al. Prevalence and factors associated with anticholinergic medication use in community-dwelling older adults: a systematic review Int J Clin Pharm, 2025.PMID 41066035
19. [19]Alkeraye S, AlRuhaimi DK. The Addition of Montelukast for the Treatment of Chronic Idiopathic Urticaria Cureus, 2021.PMID 34354881
20. [20]Gülen T, Sabato V. Advances in the Management of Mediator-Related Symptoms in Non-Advanced Systemic Mastocytosis Immunotargets Ther, 2026.PMID 42221506