Sycamore Pollen Allergy: The Urban Tree Allergen Behind Spring Rhinitis and Peach Cross-Reactivity
Sycamore pollen allergy is an IgE-mediated spring reaction to Pla a 1, an allergen recognized by up to 92 percent of mono-sensitized patients. London plane trees — planted as street trees in nearly every major US city — release pollen from March through May. Pla a 3, a lipid-transfer protein, cross-reacts with peach Pru p 3, producing heat-stable food reactions unlike the heat-labile birch OAS. Management includes intranasal corticosteroids, antihistamines, and SLIT for long-term disease modification.
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Key facts
Pla a 1, the major sycamore allergen, is recognized by up to 92 percent of mono-sensitized sycamore patients — one of the highest dominant-allergen recognition rates in tree-pollen allergy.
Pla a 3, a lipid-transfer protein in sycamore pollen, cross-reacts with peach Pru p 3 — and unlike birch PR-10 OAS, this reaction persists with cooked and canned peach because LTPs are heat-stable.
London plane (Platanus x hispanica) is the dominant street tree in New York City, Washington DC, Philadelphia, San Francisco, and Los Angeles — making urban commuters the primary exposed population for sycamore pollen.
Sycamore allergy is more commonly diagnosed in city dwellers than in suburban or rural patients, because street-tree planting concentrates pollen exposure immediately adjacent to pedestrian and commuter routes.
What Is Sycamore Pollen Allergy?
Sycamore pollen allergy is an IgE-mediated seasonal allergic disease primarily affecting residents of large US cities where London plane (Platanus x hispanica) is planted as a street tree.
New York City, Philadelphia, Washington DC, Boston, Chicago, San Francisco, and Los Angeles all have extensive London plane canopies whose pollen season runs from March through May. American sycamore (Platanus occidentalis) produces similar allergens in eastern deciduous forests.
The major allergen, Pla a 1, is an invertase-inhibitor homolog recognized by up to 92 percent of mono-sensitized patients — one of the highest rates of dominant-allergen recognition in clinical aeroallergenology. Pla a 2 (a polygalacturonase) and Pla a 3 (a nonspecific lipid-transfer protein, approximately 9 to 10 kDa) round out the allergen profile. Pla a 3 is the clinically distinctive allergen: it cross-reacts with peach Pru p 3, and unlike the heat-labile birch PR-10 OAS reactions, LTP-mediated reactions are heat-stable — patients can react to cooked peach as well as raw.
Urban sycamore allergy is underdiagnosed because city-dwelling patients often fail to connect their spring rhinitis to the mottled-bark trees lining their commute. Many have lived with the symptoms for years, attributing them to spring air quality rather than a specific pollen source they walk past every day.
Sycamore Pollen Allergy Symptoms
Recognizing symptoms early helps you get the right treatment faster.
Sneezing and rhinorrhea
moderateClassic spring rhinitis triggered by sycamore pollen exposure during commutes or outdoor time in March through May. Often worse on warm, breezy afternoons in urban areas with heavy Platanus canopy.
Nasal congestion
moderateBilateral mucosal edema producing nasal obstruction. More pronounced in patients with concurrent aspirin-exacerbated respiratory disease or nasal polyps.
Conjunctivitis
mildBilateral eye itching, redness, and tearing. Direct pollen deposition on the conjunctiva during outdoor urban exposure is the primary mechanism.
Peach food cross-reactivity (Pla a 3 LTP)
moderatePatients with elevated Pla a 3 IgE react to raw and cooked peach, nectarine, and related Rosaceae fruits. Reactions range from oral tingling to urticaria and anaphylaxis. Heat stability of LTP means cooking does NOT reliably prevent reactions.
Asthma exacerbation
severePlatanus pollen grains are small enough to penetrate the lower airway. Asthmatic patients may experience worsening bronchospasm during peak spring pollen weeks in heavily-planted urban districts.
Postnasal drip and cough
mildExcess mucosal secretions drain posteriorly, causing a persistent cough and throat-clearing that worsens through the sycamore season in spring.
Systemic LTP reaction (rare but serious)
severeIn heavily Pla a 3-sensitized patients, cooked peach or combined exercise-plus-peach consumption can trigger anaphylaxis. Seek emergency care immediately for any systemic reaction.
When to see a doctor
Sycamore pollen allergy produces two distinct clinical syndromes: seasonal allergic rhinoconjunctivitis during the spring pollen window, and LTP-mediated food cross-reactivity to peach and related Rosaceae fruits. The rhinitis symptoms are clinically similar to other spring tree-pollen allergies — sneezing, congestion, watery eyes, postnasal drip — but the LTP food cross-reactivity is clinically distinct from the more familiar birch-related OAS. When Pla a 3 sensitization is present, patients can react to peach, nectarine, apricot, cherry, plum, and peach-containing products even after cooking or canning, because LTPs are heat-stable. This is a clinically important distinction: advising an LTP-sensitized patient that cooked peach is safe (as it is for birch PR-10 OAS) would be incorrect and potentially dangerous. Reactions range from local oral itching to systemic urticaria, angioedema, or in severe cases, anaphylaxis. Seek emergency care immediately if any food cross-reactivity episode produces throat tightening, breathing difficulty, facial swelling, or dizziness, or if an episode occurs after eating cooked or canned peach (indicating likely LTP-mediated sensitization rather than mild PR-10 OAS).
Sycamore Pollen and Asthma
Sycamore pollen is a significant urban asthma trigger during spring. Pla a 1 and Pla a 2 are inhaled into the lower airway where they activate bronchial mast cells, driving eosinophilic airway inflammation and bronchospasm. In cities like New York and Los Angeles with high London plane canopy density, emergency department asthma admission rates show measurable spring spikes correlating with peak Platanus pollen counts. Patients with both sycamore sensitization and asthma should coordinate with their allergist and pulmonologist to have a spring asthma action plan in place before March. Pre-season initiation of daily controller inhaler therapy and intranasal corticosteroids is recommended. Patients who commute through high-canopy urban streets daily during peak season should consider wearing a surgical mask or N95 on high-pollen days to reduce bronchial pollen deposition.
Complications of Sycamore Pollen Allergy
The most significant complications of sycamore pollen allergy arise from the Pla a 3 LTP cross-reactivity with peach and Rosaceae foods. Unlike birch PR-10 OAS — which is generally mild and oropharyngeal — LTP reactions can be systemic and occasionally severe. Patients who have never been tested may attribute recurrent peach reactions to 'food intolerance' rather than recognizing it as an immune-mediated sycamore cross-reactivity that requires epinephrine prescription and careful food avoidance counseling. Chronic rhinosinusitis and nasal polyps can develop in patients with untreated perennial or heavy seasonal rhinitis. Social isolation and quality-of-life impairment during the spring season are significant for urban professionals who commute daily through high-canopy environments.
Systemic LTP food reactions
Pla a 3 sensitization can produce urticaria, angioedema, and anaphylaxis when eating peach or related Rosaceae fruits — even in cooked forms, unlike birch PR-10 OAS. Epinephrine auto-injector prescription is warranted.
Chronic rhinosinusitis
Repeated seasonal mucosal inflammation can progress to permanent ostiomeatal obstruction and chronic sinusitis, requiring increasing medical or surgical management over time.
Exercise-food LTP anaphylaxis
A subset of LTP-sensitized patients develop food-dependent exercise-induced anaphylaxis — reactions triggered only when exercise follows eating Pla a 3 cross-reactive foods. A board-certified allergist should evaluate any such history.
Misattribution of food reactions
Patients often do not connect their spring rhinitis to autumn peach reactions. Without correct diagnosis, LTP reactions go unmanaged and epinephrine prescriptions are delayed.
What Causes Sycamore Pollen Allergy?
Sycamore pollen allergy is caused by IgE antibodies directed against Pla a 1, with secondary sensitization to Pla a 2 and Pla a 3. London plane (Platanus x hispanica) is a wind-pollinated tree whose small pollen grains disperse effectively in spring urban air, aided by the fact that street trees are positioned close to buildings and pedestrian traffic — maximizing human exposure in ways that forest trees do not.
London plane (dominant US street tree)
Platanus x hispanica
American sycamore (eastern deciduous forests)
Platanus occidentalis
California sycamore (Pacific Coast)
Platanus racemosa
Oriental plane (southeastern Europe)
Platanus orientalis
How it works
Pla a 1 is recognized by IgE antibodies following sensitization through inhalation of sycamore pollen in spring. These IgE molecules bind to mast cells throughout the nasal and bronchial mucosa. Subsequent exposures cross-link bound IgE, triggering histamine release and the classic immediate rhinitis response. Pla a 3, the LTP allergen, additionally drives cross-reactive food reactions: ingested Pru p 3 (peach LTP) cross-links Pla a 3-specific IgE on mucosal mast cells, producing symptoms that range from OAS to systemic reactions — both because LTP survives heat and digestion.
Platanus pollen grains are approximately 15 to 20 micrometers, small enough to penetrate into the lower airway in addition to depositing on the nasal mucosa. During peak pollen days in March through May, walking under a row of flowering London planes can deliver substantial inhalational exposure in a very short time — one reason sycamore allergy is more often diagnosed in city commuters than in suburban or rural patients.
The Pla a 3 LTP cross-reactivity with peach is the most clinically significant secondary finding. LTPs are a class of small (9 to 10 kDa) plant proteins involved in pathogen defense; they are heat-stable and protease-resistant, unlike PR-10 proteins. When a patient with elevated Pla a 3 IgE eats peach — whether raw or cooked — the cross-reactive Pru p 3 protein survives digestion and can trigger systemic reactions. This is a clinically different entity from birch-related peach OAS, which is heat-labile.
Risk factors to watch for
Urban residence along London plane streets
The highest sycamore pollen exposures occur in dense urban neighborhoods where London planes are planted as street trees within 2 to 10 meters of sidewalks, buildings, and open windows.
Commuting past Platanus canopy
Daily pedestrian or cycling commutes under rows of flowering London planes in March through May deliver high cumulative pollen doses that increase sensitization risk in de-sensitized individuals.
Atopic predisposition
Patients with personal or family history of atopy (asthma, eczema, other seasonal allergies) are at higher risk for IgE sensitization to sycamore pollen on urban exposure.
Concurrent Mediterranean diet with peach consumption
LTP sensitization via Pla a 3 is amplified by concurrent consumption of peach and other Rosaceae fruits; southern European LTP syndromes are more common partly because of higher peach consumption.
The Allergy Cascade
Exposure
Allergen contact
Detection
Immune recognition
IgE Response
Antibody production
Mast Cells
Histamine release
Symptoms
Allergic reaction
1.Exposure
Allergen contact
2.Detection
Immune recognition
3.IgE Response
Antibody production
4.Mast Cells
Histamine release
5.Symptoms
Allergic reaction
Diagnosing Sycamore Pollen Allergy
Sycamore pollen allergy is diagnosed by correlating a history of spring rhinitis in an urban environment with objective IgE testing for Platanus species. The classic patient history is a city commuter who develops sneezing, congestion, and eye-watering in March through May without a clear understanding of what's causing it — often having lived with it for years without formal diagnosis. Skin prick testing with sycamore extract (Platanus t11) is the standard first-line test. Specific IgE blood testing (ImmunoCAP) provides component-level information about Pla a 1, Pla a 2, and Pla a 3. Elevated Pla a 3 IgE specifically warrants peach avoidance counseling for both raw and cooked forms, since LTP is heat-stable. Patients with Pla a 3-related peach reactions should also be tested for Ana o 3 (cashew), Cor a 8 (hazelnut), and other Rosaceae LTPs. At-home allergy testing services such as Curex offer panels covering sycamore (t11) and related allergens, with results typically within 5 days and insurance accepted. For urban patients who've never been formally evaluated, at-home testing provides objective confirmation that informs both seasonal pharmacotherapy planning and dietary counseling for the peach-cross-reactivity risk.
Skin Prick Test (SPT)
Standardized sycamore/London plane extract is applied via lancet to the forearm. A positive wheal of 3 mm or more above the negative control at 15 to 20 minutes confirms sensitization. Cross-testing with Platanus occidentalis and P. orientalis may be performed simultaneously.
Specific IgE Blood Test (ImmunoCAP)
Measures quantitative IgE against Pla a 1, Pla a 2, and Pla a 3. Component-level results determine whether the patient has primary Pla a 1 respiratory sensitization only or concurrent Pla a 3 LTP sensitization (which changes food avoidance and epinephrine counseling).
Supervised Oral Food Challenge (Peach)
For patients with ambiguous Pla a 3 results or uncertain clinical history, a supervised peach challenge in an allergist's office confirms whether cross-reactive IgE translates to a clinically significant food reaction.
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Sycamore pollen allergy treatment follows the standard pollen ladder for seasonal rhinitis, with an important additional component for Pla a 3-sensitized patients: dietary management for heat-stable LTP food cross-reactivity. Unlike birch OAS patients who can safely eat cooked peach, patients with elevated Pla a 3 IgE must avoid both raw and cooked peach, and they should carry epinephrine if their reactions have been systemic.
Pharmacotherapy focuses on pre-season intranasal corticosteroids for nasal protection, second-generation antihistamines for symptom relief, and nasal saline irrigation to flush pollen grains from the nasal cavity. Urban patients who commute past high-density Platanus canopy should plan their pharmacotherapy to be most aggressive during the 4 to 6 week peak season in their city.
Immunotherapy is a legitimate and evidence-supported option for confirmed sycamore-sensitized patients. SCIT with sycamore extract is non-standardized in the US (no Platanaceae extract on the FDA CBER standardized list), but SCIT extracts are available and used clinically. SLIT drops are an at-home alternative for patients unwilling to commit to weekly clinic injections.
Intranasal Corticosteroids
Daily nasal steroid spray is the most effective single pharmacotherapy for sycamore rhinitis. Start 2 weeks before the expected urban sycamore season in your city to establish mucosal protection.
Fluticasone (Flonase), mometasone (Nasonex), budesonide (Rhinocort), triamcinolone (Nasacort)
Clinical trials show 50 to 70 percent nasal symptom reduction with consistent use; most effective agent for congestion
Oral Second-Generation Antihistamines
H1 blockers reduce sneezing, rhinorrhea, and conjunctival itching. For LTP-sensitized patients considering raw fruit consumption, pre-medicating with antihistamine 30 minutes before eating may attenuate mild OAS but is NOT reliable protection against systemic LTP reactions.
Cetirizine (Zyrtec), fexofenadine (Allegra), loratadine (Claritin)
40 to 50 percent nasal symptom relief; inadequate protection against systemic LTP food reactions
Epinephrine Auto-injector
All patients with Pla a 3 LTP sensitization who have had systemic food reactions (urticaria, angioedema, anaphylaxis) to peach or Rosaceae fruits should carry two epinephrine auto-injectors at all times and receive training on use.
Epinephrine auto-injector (EpiPen, Auvi-Q, Symjepi)
First-line life-saving treatment for anaphylaxis; no substitute in systemic reactions
Subcutaneous Immunotherapy (SCIT)
SCIT with sycamore (Platanus) extract is available in the US as a non-standardized extract. It is used clinically for confirmed sycamore-sensitized patients, with a 6 to 12 month buildup phase followed by monthly maintenance for 3 to 5 years.
Non-standardized sycamore SCIT extract (Platanus, t11)
Clinical data from European populations (where plane pollen allergy is well-studied in Mediterranean cities) support significant symptom reduction in confirmed sensitized patients
Sublingual Immunotherapy (SLIT Drops)
SLIT drops provide at-home sycamore allergen exposure under the tongue, eliminating weekly clinic visits. No FDA-approved SLIT tablet for sycamore exists in the US. Used off-label as standard SCIT extract formulated for sublingual delivery.
Custom-formulated sycamore pollen extract SLIT drops (off-label US use)
Supported by mechanistic parallels with European plane-pollen SLIT research; no large US RCT specifically published for sycamore SLIT
| Feature | Traditional | Allergy Shots (SCIT) | Immunotherapy (SLIT)Recommended |
|---|---|---|---|
| Treats root cause | No | Yes | Yes |
| Long-lasting relief | No | Yes | Yes |
| At-home treatment | Yes | No | Yes |
| No office visits | Yes | No | Yes |
| Low side effects | Yes | Partial | Yes |
| Estimated cost | Partial | Partial | Yes |
Traditional
- NoTreats root cause
- NoLong-lasting relief
- YesAt-home treatment
- YesNo office visits
- YesLow side effects
- PartialEstimated cost
Allergy Shots (SCIT)
- YesTreats root cause
- YesLong-lasting relief
- NoAt-home treatment
- NoNo office visits
- PartialLow side effects
- PartialEstimated cost
Immunotherapy (SLIT)
Recommended- YesTreats root cause
- YesLong-lasting relief
- YesAt-home treatment
- YesNo office visits
- YesLow side effects
- YesEstimated cost
Immunotherapy for Sycamore Pollen Allergy
Instead of masking symptoms, immunotherapy retrains your immune system.
Many city-dwelling patients with sycamore allergy have spent years managing spring rhinitis with antihistamines without ever considering that the trees lining their street are the source and that a 3 to 5 year immunotherapy course might fundamentally reduce their annual burden. For patients with confirmed Pla a 1 sensitization, allergen immunotherapy — whether subcutaneous shots or sublingual drops — targets the underlying immune response rather than just suppressing symptoms each spring. European data, particularly from Mediterranean cities where Platanus is a dominant urban aeroallergen, support the clinical effectiveness of sycamore SCIT in reducing seasonal rhinitis scores and medication use. The mechanism is the same as for any aeroallergen SCIT: gradual induction of regulatory T cells and allergen-specific IgG4 blocking antibodies that dampen the IgE-mediated mast-cell response to Pla a 1. Sublingual immunotherapy, offered by providers like Curex with plan-specific pricing (https://getcurex.com/learn/curex-pricing); insurance accepted for testing and consultations plans accepted, allows urban patients to complete the 3 to 5 year desensitization course at home with daily drops — eliminating the need for weekly clinic visits during a period when they are already managing work, commute, and spring rhinitis. In a real-world Curex study of 2,897 patients on at-home sublingual immunotherapy (Tharpe et al., peer-reviewed in Frontiers in Allergy, 2026), clinically meaningful symptom improvement rose to 45% of patients by two years and quality-of-life improvement reached 90.7%. There is no FDA-approved SLIT tablet for sycamore in the US. Note that immunotherapy addresses the pollen rhinitis component of sycamore allergy; the Pla a 3 LTP food cross-reactivity with peach requires ongoing avoidance and epinephrine management independently.
Confirm Sensitization and Component Pattern
IgE testing identifies Pla a 1 (rhinitis), Pla a 2, and Pla a 3 (food cross-reactivity). Patients with elevated Pla a 3 need concurrent food avoidance counseling and epinephrine prescription independent of immunotherapy decisions.
Begin Before Spring Season
Start immunotherapy in late summer or early fall to complete or significantly progress through buildup before March pollen season. Immunotherapy is not typically started during active pollen season.
Buildup and Maintenance
Weekly increasing doses of sycamore extract (SCIT) or daily under-the-tongue drops (SLIT) build immune tolerance over 6 to 12 months of buildup, then continue as maintenance for 3 to 5 years total.
Annual Reassessment
Symptom scores, rescue medication use, and Pla a 3 IgE levels are monitored annually. Most patients notice meaningful improvement by their second treated spring season.
“European clinical data show significant rhinitis symptom reduction in Platanus-sensitized patients completing immunotherapy courses”
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Living With Sycamore Pollen Allergy in the City
Urban patients with sycamore allergy navigate a distinctive challenge: the allergen is woven into the physical infrastructure of their daily environment in a way that no rural pollen allergy quite matches. The London plane trees lining your commute route, shading your building entrance, and filling the park across the street are both beautiful and, for a few weeks each spring, the primary driver of your rhinitis. The most effective mindset is to treat sycamore season like a planned annual project: start nasal steroids in late February, check pollen counts daily in March and April, plan outdoor activities around count thresholds, and accept that the most beautiful days of spring (warm, dry, breezy) are often the worst pollen days. Patients who engage proactively rather than reactively consistently report better seasonal outcomes. For patients with Pla a 3 LTP sensitization, year-round peach and Rosaceae avoidance requires reading labels and making informed restaurant choices — but most patients adapt to this within a season once they understand the heat-stability distinction.
Know Your City's Sycamore Map
London planes are easy to identify by their distinctive mottled tan-and-gray peeling bark and large palmate leaves. Identify which streets on your daily commute have high Platanus density and plan alternative routes for peak-season days above your personal tolerance threshold.
The LTP Kitchen Rule
If Pla a 3 is elevated on your component test, the kitchen rule is simple: avoid peach and close Rosaceae relatives in all forms — raw, cooked, canned, and in products. This is unlike the birch OAS kitchen rule where cooking is usually safe. Carry your epinephrine at all times.
Apartment-Level Exposure Control
Keep windows closed from 5 AM to noon during sycamore season. Use AC for ventilation rather than open windows. Run a HEPA air purifier in your bedroom continuously. Wash bedding weekly during peak weeks to remove accumulated pollen.
When Is Sycamore Pollen Season?
Sycamore pollen season runs from March through May across the temperate US, with timing shifted earlier in warmer urban environments (Los Angeles, San Francisco) and later in northern cities (Boston, Minneapolis). Urban heat island effects in downtown districts can advance pollen release by 1 to 2 weeks compared to suburban areas in the same city. In Mediterranean climates (Los Angeles, San Francisco) and southern cities with early spring warming, Platanus pollen can begin in late February. In New York, Philadelphia, and DC, peak season typically runs through mid-May. NAB stations in Mediterranean cities (Madrid, Barcelona) record plane pollen as the dominant urban spring aeroallergen — providing extensive allergenicity data that applies to North American urban patients as well.
March - May
high intensity
June - August
low intensity
September - November
low intensity
Reducing Sycamore Pollen Exposure
For urban patients, sycamore pollen avoidance requires navigating streets that are specifically designed to maximize human-tree proximity. Complete avoidance is impractical, but strategic exposure management meaningfully reduces cumulative pollen dose and symptoms during the 4 to 6 week peak season. The most practical measures are route planning (choosing streets with lower Platanus canopy density when possible), timing outdoor exposure for afternoons when pollen counts are typically lower than mornings, and keeping apartment or office windows closed during the 5 AM to noon window when pollen release is highest.
Check Local NAB Pollen Counts Daily
AAAAI NAB stations in major cities report spring tree pollen counts including Platanus. On high-count spring days, plan indoor meetings and postpone discretionary outdoor time.
HEPA Filtration in Bedroom and Office
Run HEPA air purifiers in spaces where you spend the most time. Request window closure and HEPA filtration in your workplace during sycamore season if possible.
Commute Timing and Route
Plan commutes for midday or afternoon rather than early morning when possible. Consider alternate walking or cycling routes through parks rather than heavily-planted urban streets during peak season.
Shower After Outdoor Urban Exposure
Pollen adheres to hair and clothing during outdoor commutes. Showering and changing clothes on returning home prevents indoor pollen accumulation on bedding and furniture.
Peach and Rosaceae Avoidance for Pla a 3-Positive Patients
If component testing shows elevated Pla a 3, avoid raw and cooked peach, nectarine, apricot, and related Rosaceae fruits year-round. Unlike birch PR-10 OAS, cooking does not make these safe.
Outlook for Sycamore Pollen Allergy
Sycamore pollen allergy is a manageable chronic condition. The rhinitis component responds well to pharmacotherapy and immunotherapy, with most patients achieving good seasonal control within 1 to 2 years of appropriate treatment. The Pla a 3 LTP component requires indefinite food avoidance management but generally does not worsen in severity once appropriate epinephrine prescription and dietary counseling are in place. With immunotherapy, the trajectory is consistently favorable: European data support progressive seasonal improvement over 3 to 5 years, with sustained benefit after treatment completion. Patients who complete SCIT or SLIT courses often describe being essentially asymptomatic during subsequent March-through-May seasons that previously required antihistamines, nasal sprays, and disrupted commutes.
Key takeaways
Sycamore pollen rhinitis responds well to nasal steroids, antihistamines, and immunotherapy
Pla a 3 LTP cross-reactivity with peach is heat-stable — cooking does NOT make peach safe for Pla a 3-positive patients
All patients with Pla a 3 elevation and any systemic food reaction history should carry epinephrine auto-injectors
No FDA-approved SLIT tablet exists for sycamore; SCIT or SLIT drops (off-label) are available through allergists
Diet and Sycamore Pollen Cross-Reactivity
Dietary management is critical for patients with Pla a 3 LTP sensitization — a finding in a subset of sycamore-allergic patients. Pla a 3 cross-reacts with peach Pru p 3 (LTP), and LTP proteins are heat- and protease-stable, meaning they survive cooking, canning, and digestion. This makes LTP cross-reactivity clinically different and potentially more serious than birch PR-10 OAS. Patients with Pla a 3 elevation should avoid raw and cooked forms of peach, nectarine, plum, apricot, and cherry, and should discuss with their allergist whether hazelnut Cor a 8 (also LTP) requires avoidance. These patients should carry epinephrine auto-injectors at all times.
Foods to limit
Raw peach
Pru p 3 (peach LTP) cross-reacts strongly with Pla a 3 — reactions can range from OAS to anaphylaxis, including in peeled peach where most LTP is concentrated in the skin but present in flesh.
Cooked peach and canned peach
Unlike birch PR-10 OAS, LTP proteins are heat-stable and survive canning and cooking — cooked peach is NOT reliably safe for Pla a 3-positive patients.
Peach-containing products
Peach jam, peach juice, peach-flavored products, and peach in baked goods all retain LTP activity and require the same avoidance caution as whole peach.
When a New Yorker tells me they react to peach but not to apple or cherry, I immediately think LTP — and I think about the London planes lining their street. Pla a 3 cross-reacts with peach Pru p 3, and that reaction doesn't go away when you bake the peach into a pie. That's the key clinical distinction from birch OAS.
Frequently Asked Questions
Sycamore pollen season runs from March through May across most of the United States, with timing shifted slightly earlier in warmer cities like Los Angeles and San Francisco (beginning in late February) and extending through mid-May in colder northern cities like Boston and Minneapolis. Urban heat island effects advance pollen release by 1 to 2 weeks in downtown districts compared to suburban locations in the same metropolitan area. NAB stations in major cities publish daily Platanus pollen counts that provide the most accurate guidance on your local season timing.
Medical References
- [1]Lauer I, Duffort C, Vieths S, Wangorsch A, et al. Structural mimicry of lipid transfer proteins from Platanus acerifolia pollen and peach. Clin Exp Allergy. 2007;37(2):261–269.
- [2]Asturias JA, Ibarrola I, Amat P, Tella R, et al. Purification and characterization of Pla a 1, the major Platanus acerifolia pollen allergen. Clin Exp Allergy. 2002;32(11):1628–1636.
- [3]Wangorsch A, Larenas-Linnemann D, Nerkamp J, et al. Platanus acerifolia pollen sensitization and allergy. Allergy. 2016.
- [4]D'Amato G, Cecchi L, Bonini S, et al. Allergenic pollen and pollen allergy in Europe. Allergy. 2007;62(9):976–990.
- [5]WHO/IUIS Allergen Nomenclature Sub-Committee. Platanus acerifolia (Pla a) allergen list. allergen.org.
- [6]Cox L, Nelson H, Lockey R, et al. Allergen immunotherapy: a practice parameter third update. J Allergy Clin Immunol. 2011;127(1 Suppl):S1–55.
- [7]Thermo Fisher Scientific. Allergen Encyclopedia. Phadia.
- [8]Tharpe C, et al. Real-world outcomes of personalized sublingual immunotherapy for environmental allergies delivered through a telemedicine platform. Frontiers in Allergy. 2026;7:1865860.
- [9]Schaffer FM, Naples AR, Ebeling M, Hulsey TC, Garner LM. The safety of self-administered allergen immunotherapy during the buildup and maintenance phases. Int Forum Allergy Rhinol. 2015;5(2):149-156.
This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about a medical condition. Content reviewed by board-certified allergists at Curex.
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