What it is:An IgE-mediated inflammatory response in the nasal mucosa. A sensitized patient inhales an allergen (pollen, dust mite, animal dander, mold), mast-cell-bound IgE recognizes it, and the mast cell dumps histamine and friends into the tissue. The result is the classic quartet: sneezing, rhinorrhea, itching, and congestion.
The core problem:There are really two separate reactions happening on two different timelines, and most of the drug class map falls straight out of that fact. An immediatereaction (seconds to minutes) is histamine-driven and causes sneezing, itch, and rhinorrhea. A late-phasereaction (4–8 hours later) is cytokine-driven and causes the stubborn, chronic congestion. Antihistamines crush the immediate phase. They do almost nothing for the late-phase congestion, which is why a patient who is "still stuffy" on an antihistamine isn't failing therapy, they're on the wrong drug class for that symptom.
What you do about it:Match the drug to the dominant symptom (or use an intranasal steroid, which covers both phases at once), avoid triggers where practical, and step up or combine therapy if a single agent isn't cutting it.
The whole chapter organizes around one idea: sneeze/itch/rhinorrhea/eyes = histamine = antihistamines; congestion = late-phase inflammation = decongestants (short-term) or intranasal steroids (real fix).Every drug choice below is really just picking which piece of that reaction you're targeting.
Allergic rhinitis used to be split into "seasonal" and "perennial." The current terms are seasonaland persistent, and a lot of patients have both at once.
| Type | Trigger | Pattern |
|---|---|---|
| Seasonal (hay fever) | Tree, grass, and weed pollens | Predictable, spring and/or fall, more acute/intense symptoms |
| Persistent | Dust mites, animal dander, molds (nonseasonal allergens) | Year-round, less variable, more chronic |
Many patients have persistent baseline symptoms with seasonal flares layered on top. This distinction matters for treatment timing (start seasonal therapy beforethe season, not after symptoms start) and it changes which intranasal antihistamine guidelines prefer, azelastine and olopatadine are favored for seasonal disease but not persistent.
Airborne allergen particles land on the nasal mucosa during inhalation. In a genetically predisposed person, lymphocytes process the allergen and churn out antigen-specific IgE, which coats mast cells in the nasal tissue. That's sensitization; nothing happens clinically yet. The disease shows up on reexposure, when the allergen cross-links IgE already sitting on those mast cells and triggers degranulation.
| Phase | Timing | Mediators | Symptoms it causes | Drug that targets it |
|---|---|---|---|---|
| Immediate | Seconds to minutes | Preformed histamine, plus newly made leukotrienes, prostaglandins, tryptase, kinins from the arachidonic acid cascade | Vasodilation, vascular permeability, rhinorrhea, itching, sneezing, some obstruction | Antihistamines |
| Late-phase | 4–8 hours after exposure | Cytokines released from mast cells and T-helper lymphocytes | Persistent inflammation, chronic nasal congestion | Intranasal corticosteroids |
Histamine explains sneezing, itching, and rhinorrhea, but congestion is mostly a late-phase, cytokine-driven eventthat antihistamines were never built to touch. If a patient's chief complaint is nasal blockage rather than sneeze/itch/drip, an antihistamine is the wrong monotherapy, reach for a decongestant (short-term) or, better, an intranasal corticosteroid that suppresses the late-phase reaction directly.
Histamine acting on H1 receptors is also responsible for part of the symptom picture through an indirect route: it increases capillary permeability and drives the anticholinergic-style drying effect that antihistamines exploit to reduce nasal, salivary, and lacrimal secretions.
Core symptoms: clear rhinorrhea, sneezing, nasal congestion, postnasal drip, allergic conjunctivitis, and itching of the eyes, ears, or nose.Loss of smell or taste can occur and often points to underlying sinusitis or nasal polyps. Postnasal drip frequently shows up as a nagging cough or hoarseness rather than an obviously "nasal" complaint.
Allergic shiners(dark circles under the eyes from venous congestion), a transverse nasal creasefrom repeated upward nose-rubbing (the "allergic salute"), adenoidal/mouth breathing, edematous turbinates coated in clear secretion, tearing, and periorbital swelling. These are classic exam-question findings in kids and are easy to miss if you're only picturing the adult presentation.
What untreated disease costs the patient:disturbed sleep, malaise, fatigue, and measurably worse school or work performance. This isn't just a nuisance diagnosis, it has real functional impact, which matters when you're counseling a patient who wants to "just push through" without treatment.
Associated conditions and complicationsworth screening for: asthma, chronic rhinosinusitis, otitis media, nasal polyposis, respiratory infections, dental malocclusions, and recurrent/chronic sinusitis with epistaxis. Allergic rhinitis and asthma travel together often enough that poorly controlled rhinitis is a reasonable thing to check when an asthma patient isn't at goal.
Diagnosis starts with a careful history: symptom description, environmental exposures, prior therapy and response, current medications, any prior nasal injury or surgery, and family history of atopy.
| Test | What it does | Notes |
|---|---|---|
| Percutaneous (skin prick) testing | Immediate-type hypersensitivity testing | Safer and more widely accepted than intradermal testing; first-line allergy test |
| Intradermal testing | Immediate-type hypersensitivity testing | Reserved for confirmation in patients who need it |
| RAST (radioallergosorbent test) | Detects antigen-specific IgE in blood | Highly specific, but somewhat less sensitive than skin testing |
Goals of treatment:minimize or prevent symptoms, prevent long-term complications, avoid or minimize medication side effects, keep therapy economical, and preserve the patient's normal lifestyle.
Pick the initial single agent based on which symptoms dominate, then reassess and escalate:
| Dominant symptom | First pick |
|---|---|
| Sneezing, itching, rhinorrhea, ocular symptoms | Antihistamine |
| Nasal congestion | Decongestant (systemic) |
| Sneezing, itching, rhinorrhea, andcongestion | Intranasal corticosteroid |
After starting therapy, assess efficacy first.Symptoms controlled but side effects bothersome → adjust the dose or switch to another agent in the samecategory. Symptoms not controlled → check adherence first. If adherent and still uncontrolled → switch to a different therapeutic category, or add a second agent from a different category. Still not controlled after that → consider montelukast.At any point, reassess whether the patient is a candidate for immunotherapy, initially and again if pharmacotherapy isn't cutting it.
Duration:for persistent disease, once symptoms are controlled with minimal side effects, continue and reassess in 6–12 months.For seasonal disease, continue until the end of the patient's allergy season and discuss with them when to restart next year. Recent guidelines actually favor starting with an intranasal corticosteroidrather than working up to one, since it's the only class that covers both the immediate and late-phase reaction.
| Oral Antihistamines, Nonselective (1st-generation) | ||
| Drug | Adult/adolescent dose | Pediatric dose |
|---|---|---|
| Chlorpheniramine maleate | 4 mg q6h; ER 12 mg q12h | 6–11 yr: 2 mg q4–6h · 2–5 yr: 1 mg q4–6h |
| Clemastine fumarate | 1.34 mg BID up to 2.68 mg TID (max 8.04 mg/day) | 6–11 yr: 0.67 mg BID (max 4.02 mg/day) |
| Diphenhydramine HCl | 25–50 mg q4–6h (max 300 mg/day) | 6–11 yr: 12.5–25 mg q4–6h (max 150 mg/day) |
| Oral Antihistamines, Peripherally Selective (2nd-generation) | ||
| Cetirizine | 5–10 mg once daily | 6 mo–5 yr: 2.5 mg daily · 6–11 yr: 5–10 mg daily |
| Fexofenadine | 60 mg q12h or 180 mg once daily | 2–11 yr: 30 mg once daily |
| Levocetirizine | 5 mg once daily (evening) | 6 mo–5 yr: 1.25 mg daily · 6–11 yr: 2.5 mg daily (evening) |
| Loratadine | 10 mg once daily | 2–5 yr: 5 mg daily · 6–12 yr: 10 mg daily or 5 mg BID |
| Intranasal / Ophthalmic Antihistamines | ||
| Azelastine (nasal) | 1–2 sprays/nostril once or twice daily | 2–11 yr: 1 spray/nostril BID |
| Olopatadine (nasal) | 2 sprays/nostril BID | 6–11 yr: 1 spray/nostril BID |
| Bepotastine (ophthalmic) | 1 drop affected eye(s) BID | 2–11 yr: same |
| Olopatadine (ophthalmic) | 1 drop affected eye(s) BID, 6–8h apart | 3–11 yr: same |
| Decongestants | ||
| Pseudoephedrine (oral) | 60 mg q4–6h · SR 120 mg q12h · CR 240 mg daily | 6–11 yr: 30 mg q4–6h · 2–5 yr: 15 mg q4–6h |
| Phenylephrine (oral) | 0–20 mg q4h | 6–11 yr: 5 mg q4h · 2–5 yr: 2.5 mg q4h |
| Oxymetazoline (nasal) | 2–3 sprays BID, max 3 days | 6–11 yr: same, max 3 days |
| Phenylephrine (nasal) | 2–3 sprays q4h (0.25–1%), max 3 days | 2–5 yr: 0.125% · 6–11 yr: 0.25% |
| Intranasal Corticosteroids | ||
| Beclomethasone | 1–2 sprays/nostril BID (or 2 sprays/nostril once daily, formulation-dependent) | 4–11 yr: 1 spray/nostril once daily · 6–11 yr: 1 spray/nostril BID |
| Budesonide | 1 spray/nostril once daily | 6–11 yr: same |
| Fluticasone | 1–2 sprays/nostril once daily | 2–11 yr: 1 spray/nostril once daily |
| Mometasone | 2 sprays/nostril once daily | 2–11 yr: 1 spray/nostril once daily |
| Triamcinolone | 2 sprays/nostril once daily | 2–11 yr: 1 spray/nostril once daily |
| Other Nasal Agents & Montelukast | ||
| Cromolyn (nasal) | 1 spray/nostril 3–4x daily | 2–11 yr: same |
| Ipratropium (nasal) | 2 sprays/nostril 4x daily | 5–11 yr: same |
| Montelukast | 10 mg PO once daily | 6–14 yr: 5 mg chewable daily · 2–5 yr: 4 mg daily · 6–23 mo: 4 mg granules daily |
H1-receptor antagonists work by preventinghistamine from binding, not by reversing effects that already happened. That's why they only fully work when dosed 1–2 hours beforeanticipated exposure, and why seasonal-allergy patients should start therapy before the season begins rather than after symptoms show up.
Guidelines default to trying a nonsedating (2nd-gen) agent first.But "1st-gen vs 2nd-gen" is a generalization, not a guarantee, individual agents vary in how sedating they actually are, so judge each drug on its own profile rather than assuming every 2nd-gen agent is equally clean. Also: tolerance to 1st-gen sedation can develop after about 4 daysof continued use, which matters if a patient dismisses an older, cheaper agent purely because of day-one drowsiness.
| Class | Agents | Sedation | Anticholinergic effect |
|---|---|---|---|
| Alkylamine (nonselective) | Brompheniramine, chlorpheniramine, dexchlorpheniramine | Low | Moderate |
| Ethanolamine (nonselective) | Carbinoxamine, clemastine, diphenhydramine | Moderate–high | High |
| Phenothiazine (nonselective) | Promethazine | High | High |
| Piperidine (nonselective) | Cyproheptadine | Low | Moderate |
| Piperazine (peripherally selective) | Cetirizine, levocetirizine | Low–moderate | Low–none |
| Piperidine (peripherally selective) | Desloratadine, fexofenadine, loratadine | Low–none | Low–none |
Why sedation and anticholinergic effects both matter clinically:the anticholinergic drying effect is actually part of why antihistamines relieve symptoms, it cuts nasal, salivary, and lacrimal hypersecretion. But that same mechanism causes dry mouth, urinary hesitancy/retention, and constipation, so use caution in patients predisposed to urinary retention, and in those with elevated intraocular pressure, hyperthyroidism, or cardiovascular disease. Sedation itself can occasionally be turned into a feature, it may help a patient whose rhinitis symptoms are wrecking their sleep. Other side effects: appetite loss, nausea, vomiting, epigastric distress, often improved by taking the dose with food or a full glass of water.
Azelastineis prescription-only, relieves sneezing/rhinorrhea/pruritus, and comes in two strengths: 0.1% is labeled for children with seasonal allergies, 0.15% is adults-only for either type. Its systemic availability is roughly 40%, so counsel on drowsiness even though it's applied locally; it can also cause drying and lose effectiveness over time. Olopatadinenasal spray is a more selective H1 antagonist and tends to cause less drowsiness. Guidelines favor intranasal antihistamines for seasonal, not persistent, disease, which is easy to mix up since the intuition usually runs the other way for nasal-delivered drugs.
Ophthalmic antihistamines(levocabastine, olopatadine, bepotastine) target the conjunctivitis piece specifically and pair well with a nasal corticosteroid when ocular symptoms persist despite adequate nasal control. Systemic oral antihistamines usually handle allergic conjunctivitis fine on their own too.
Decongestants are sympathomimetics acting on α1 receptorsin nasal mucosa: vasoconstriction shrinks swollen, engorged mucosa and improves airflow. Mechanistically, α1 stimulation constricts the venous capacitance vessels in the nose, directly reducing mucosal volume. They should only be used when congestion is actually present, and they pair naturally with antihistamines since the two classes cover different parts of the symptom picture.
Topical (nasal spray) decongestants must be limited to 3–5 days.Beyond that, you risk rhinitis medicamentosa: rebound vasodilation and congestion that gets worse the more spray the patient uses, with diminishing response. Treatment is abrupt discontinuation (rebound congestion can linger days to weeks) or a slow taper of frequency/concentration, ideally paired with a nasal corticosteroid to bridge the gap since steroids take several days to kick in on their own.
| Agent | Duration of action |
|---|---|
| Phenylephrine HCl | Short acting, up to 4 hours |
| Naphazoline / tetrahydrozoline HCl | Intermediate, 2–6 hours |
| Oxymetazoline / xylometazoline HCl | Long acting, up to 12 hours |
Oral phenylephrine has poor oral bioavailability as a decongestant, which is exactly why patients (and pharmacists) often notice it's less effective than pseudoephedrine. Phenylephrine replaced pseudoephedrine in most OTC combination products not because it works better, but because pseudoephedrine is restricted to behind-the-counter sale with purchase limitsdue to its use as a methamphetamine precursor. Doses of pseudoephedrine up to 180 mg produce no measurable change in blood pressure or heart rate; 210–240 mg can raise both. Avoid systemic decongestants in hypertensive patients unless truly necessary, and know that combining pseudoephedrine with an MAOI can trigger a severe hypertensive reaction. Even at normal doses, pseudoephedrine can cause mild CNS stimulation (this tracks with the broader α1-agonist side effect pattern: appetite suppression from reduced GI blood flow, urinary retention from bladder sphincter constriction, reflex bradycardia from the baroreflex responding to the BP rise, and photophobia from mydriasis).
Topical decongestants(applied as drops/sprays) act locally with little to no systemic absorption, but bring their own local side effects: burning, stinging, sneezing, and mucosal dryness. Use the smallest effective dose as infrequently as possible (e.g., only at bedtime) and cap therapy at 3 days. Combination antihistamine/decongestant productsmake pharmacologic sense (different mechanisms), but remember the two components have different appropriate dosing schedules: the antihistamine should be taken on a fixed schedule, while the decongestant should only be used PRN when congestion is actually present. Counsel patients to check labels for therapeutic duplication and keep combination products to short courses.
Mechanistically, intranasal steroids hit the disease from multiple angles: they reduce inflammatory mediator release, suppress neutrophil chemotaxis, reduce intracellular edema, cause mild vasoconstriction, and, critically, inhibit the mast-cell-mediated late-phase reaction. That last piece is why this is the only class that relieves sneezing, rhinorrhea, itching, andcongestion.
Some improvement can show up within a few days, but peak response can take 2–3 weeks.If you don't warn the patient up front, they'll conclude "this isn't working" around day 5 and stop. Tell them this is a marathon drug, not a rescue drug, and that dosage can often be reduced once control is achieved.
Technique matters as much as the drug:clear blocked nasal passages with a decongestant or saline irrigation beforethe spray so it actually penetrates, and instruct patients to avoid sneezing or blowing their nose for at least 10 minutes afterward so the dose isn't lost. Side effects are generally minimal: sneezing, stinging, headache, epistaxis, and rare Candida albicans infection.
Recent guidelines put intranasal corticosteroids forward as initial therapy, not a step-up option, especially useful for seasonal disease if started before allergen exposure begins. They're also the go-to for persistent disease, either alone or layered with a systemic antihistamine.
Cromolyn sodiumis a nonprescription mast cell stabilizer that prevents antigen-triggered degranulation before mediators (including histamine) are ever released, that's a preventive mechanism, not a reversal of an ongoing reaction. Clear the nose before dosing and inhale gently during administration to spread it across the nasal lining. It must be redosed every 6 hoursto maintain effect, a real adherence challenge compared to once- or twice-daily options. For seasonal disease, start it just before the season and continue throughout; for persistent disease, improvement can take 2–4 weeks, so bridge with an antihistamine or decongestant during that window. Main side effect is local irritation (sneezing, stinging).
Ipratropium bromidenasal spray is an anticholinergic with local antisecretory action, useful specifically for rhinorrhea. It is notpart of standard first-line guideline algorithms and should be reserved for patients who fail or can't tolerate other therapies. Adverse effects are mild: headache, epistaxis, nasal dryness.
Montelukast is a leukotriene-receptor antagonist and it is third-line, tried after antihistamines and intranasal corticosteroids have been optimized, not reached for early despite brand-name recognition. As monotherapy it's no better than a peripherally selective antihistamine, and it's lesseffective than an intranasal corticosteroid. Where it earns its place: montelukast plus an antihistamine beats an antihistamine alone.It's approved for persistent allergic rhinitis down to 6 months of age and seasonal disease down to 2 years, and monotherapy is a reasonable option specifically in kids who have both mild persistent asthma and coexisting allergic rhinitis.
Immunotherapy means dosing a patient with the actual antigen(s) driving their symptoms to induce tolerance, so natural exposure stops triggering a reaction. Proposed mechanisms include induction of IgG-blocking antibodies, long-term reduction in specific IgE, reduced recruitment of effector cells, a shift in T-cell cytokine balance, T-cell anergy, and altered regulatory T-cell activity.
| Subcutaneous (SCIT) | Sublingual (SLIT) | |
|---|---|---|
| Available for | Broad range of allergens | Limited list: ragweed, certain grasses, house dust mite |
| Schedule | Very dilute doses 1–2x/week initially, up-titrated to max tolerated/planned dose, then maintained at increasing intervals for years | Ragweed/grass: start 12 weeks before season, continue through it. Dust mite: year-round (persistent trigger) |
| First dose | In-office by definition | Given in-office with 30-minute observation, then may continue at home |
| Home safety requirement | N/A, always administered in a monitored setting | Auto-injectable epinephrine must be prescribed and on handbefore home dosing begins |
| Age restriction | None specific | Approved for age 18 and older only |
| Common adverse effects | Mild induration/swelling at injection site; rare but severe: generalized urticaria, bronchospasm, laryngospasm, vascular collapse, anaphylaxis death | Pruritus of mouth/ears/tongue, throat irritation, mouth edema |
SLIT feels lower-risk because there's no needle, but severe reactions are still possible, which is exactly why home SLIT patients need their own epi-pen on hand and why the first dose always happens under 30 minutes of in-office observation. If a SCIT patient has a severe reaction, treat with epinephrine, antihistamines, and systemic corticosteroids.
Good candidates:strong history of severe symptoms not controlled by avoidance and pharmacotherapy, or patients who can't tolerate drug side effects. Poor candidates:conditions that would make an anaphylactic-type reaction hard to tolerate, impaired immune systems, and a history of nonadherence (immunotherapy only works if the schedule is followed for years). Year-round SCIT dosing outperforms seasonal-only injection schedules.
| Parameter | When | Watching for |
|---|---|---|
| Target symptom severity(sneeze, itch, rhinorrhea, congestion, ocular) | Every follow-up | Which symptoms remain uncontrolled, to guide category switch vs add-on |
| Adherence | Before escalating therapy | Nonadherence masquerading as treatment failure, the algorithm explicitly checks this before switching drug categories |
| Sedation / anticholinergic effects | Ongoing, especially with 1st-gen agents | Driving impairment, urinary retention, constipation; consider agent switch within class first |
| Duration of topical decongestant use | Every refill/counseling touchpoint | Use beyond 3–5 days, rhinitis medicamentosa risk |
| Blood pressure/heart rate | Patients on systemic decongestants, especially hypertensive patients | BP/HR rise, more likely at pseudoephedrine doses >180–240 mg |
| Nasal mucosa | Chronic intranasal corticosteroid use | Epistaxis, Candida infection |
| Response timeline expectations | Weeks 1–3 after starting an intranasal steroid or cromolyn | Premature discontinuation before peak effect is reached |
| Quality of life / functional status | Periodic follow-up | Sleep quality, fatigue, concentration, participation in normal activities |
| Immunotherapy patients | Every dose (SCIT in-office; SLIT first dose, then per visit) | Local reaction vs systemic/anaphylactic reaction; confirm epi-pen availability for home SLIT |