Johnson Grass Allergy Shots: The Invasive Weed With 5 Named Allergens
Johnson grass allergy shots (SCIT) target Sorghum halepense — the invasive weed with five WHO/IUIS allergens (Sor h 1, 2, 7, 13, 23), the most of any Panicoideae species, yet still using a non-standardized extract. Its 7-foot canopy launches pollen plumes drifting 5–10 km, sensitizing 35–55% of Plains grass-allergic patients — most never specifically tested for it.
About Curex’s SCIT program
Curex’s at-home allergy shots (SCIT) are coming soon and focus on the most common environmental allergens:
- • Pollens — tree, grass, weed & ragweed
- • Pet dander — cat & dog
- • Dust mites
- • Molds — Alternaria & mold mix
Johnson Grassis covered here for general education and may not be part of Curex’s current treatment set. Join the waitlist and our care team will help confirm your options.
Johnson Grass Allergy Immunotherapy: How It Works
Allergy immunotherapy is the only long-term treatment that re-trains the immune system to stop overreacting to johnson grass — rather than just masking symptoms with antihistamines or steroids. By gradually exposing the body to controlled doses of johnson grass allergen, immunotherapy shifts the underlying allergic response and produces relief that often outlasts treatment by 7–10 years.
There are two evidence-based forms of johnson grass immunotherapy used today, both built on the same desensitization principle but delivered very differently.
of sustained relief after a complete immunotherapy course — the only allergy treatment with proven long-term effect after stopping.
Allergy Shots (SCIT)
Weekly injections of johnson grass extract in a clinic, escalating over 3–6 months until a maintenance dose is reached. Continued monthly for 3–5 years. Longest clinical track record for johnson grass allergy.
- Strongest evidence base for severe and polysensitized patients
- Covered by most insurance plans
- Requires 50–100+ in-person clinic visits across the full course
- Or at home with no clinic visits— Curex’s Virtual Shot Room model delivers the same SCIT program with live video supervision by trained Curex clinical staff for the first injection from each new vial or concentration and restarts after gaps or reactions.
Allergy Drops / Tablets (SLIT)
Daily drops or dissolvable tablets containing johnson grass extract, held under the tongue at home. Same desensitization principle, delivered without injections. WHO-recognized as an effective form of allergy immunotherapy since 2001.
- Taken at home — no weekly clinic trips, no needles
- Lower systemic reaction rate than allergy shots
- Curex offers prescription johnson grass immunotherapy drops with allergist oversight
The rest of this page goes deep on allergen-specific immunotherapy with shots — protocol, efficacy data, side effects, and cost. If you’d rather skip the clinic and treat johnson grass allergy with at-home drops, see how Curex sublingual immunotherapy compares below.
What is Johnson Grass?
The biology, taxonomy, and clinical fingerprint of Johnson Grass — the foundation of how SCIT targets it.
Johnson grass (Sorghum halepense) towering above a Kansas sorghum field — its 6–8 foot canopy enables pollen plumes that drift 5–10 km into suburban airsheds from agricultural land, making it the dominant invisible allergen for many Plains allergy patients.
- Scientific name
- Sorghum halepense
- Family
- Poaceae (Panicoideae)Grass family — warm-season Panicoideae
- Type
- Perennial warm-season agricultural weed grass pollen
- Native to
- Mediterranean basin / North Africa; named for Alabama plantation owner William Johnson (1840s introduction); now USDA noxious weed in 19 US states
- Allergen proteins
- Sor h 1 (major) — Group 1 beta-expansin, >85% sensitization in Johnson-allergic patients (Avjioglu et al., 1993)Sor h 2 — Group 2/3 expansin-likeSor h 7 — polcalcin (pan-allergen)Sor h 13 — polygalacturonaseSor h 23 — polygalacturonase-related
- Particle size
- 30–35 μm
- Avoidance difficulty
- Nearly impossible
How Johnson Grass Allergy Presents
Symptoms by body system — useful for distinguishing Johnson Grass sensitivity from overlapping allergies and infections.
Respiratory
- Sneezing episodes and severe rhinorrhea during the July–September Plains and Southeast pollen peak
- Nasal congestion from agricultural pollen drift — symptomatic even miles from the nearest Johnson grass stand
- Asthma exacerbations in farmworkers and rural residents during harvest periods when Johnson grass is disturbed
- Wheezing and chest tightness on high-pollen mornings when the 7-foot canopy releases pollen plumes
- Prolonged post-nasal drip cough persisting through late summer and into October in southern states
Ocular
- Bilateral eye itching and tearing during peak July–August Plains pollen events
- Conjunctival redness and discharge on high-pollen days in agricultural counties
- Eyelid swelling after outdoor agricultural work in infested fields
- Contact lens intolerance during peak Johnson grass pollen weeks
Dermal
- Contact urticaria after direct handling or cutting Johnson grass in field settings
- Skin rash in farmworkers with occupational contact with the grass stalks and seedheads
- Eczema flares during high-pollen late-summer weeks
Systemic
- Fatigue and reduced work capacity in agricultural workers during the July–September season
- Sleep disruption from nighttime nasal congestion during peak pollen months
- Heat-amplified symptoms on hot Plains summer days when pollen release is maximal
- Quality-of-life impairment across the 3-month late-summer agricultural pollen window
In Oklahoma City and Dallas clinics, I regularly see patients who are symptomatic all of July and August and assumed it was ragweed. When I run component-resolved testing, many have strong Sor h 1 IgE with relatively weak Phl p 5 — that's a Johnson grass primary sensitization. They've been undertreated for years because no one tested for it specifically.
When & Where Johnson Grass Peaks
Allergen intensity by month and by state. Useful for timing SCIT start dates and travel planning.
12-Month Intensity
Peak: July–August across the Plains and Southeast; later than Bermuda and bahia, overlapping with the onset of ragweed season· June–October; later and longer in the deep South (Arkansas, Mississippi, Alabama)
US Exposure Map
11 high-intensity statesExposure intensity by state (text version)
- ME:
- Low
- VT:
- Low
- NH:
- Low
- WA:
- Low
- MT:
- Low
- ND:
- Low
- MN:
- Low
- WI:
- Low
- MI:
- Low
- NY:
- Low
- MA:
- Low
- OR:
- Low
- ID:
- Low
- WY:
- Low
- SD:
- Low
- IA:
- Moderate
- IL:
- Moderate
- IN:
- Moderate
- OH:
- Moderate
- PA:
- Low
- NJ:
- Low
- CT:
- Low
- RI:
- Low
- CA:
- Moderate
- NV:
- Low
- UT:
- Low
- CO:
- Low
- NE:
- Moderate
- MO:
- High
- KY:
- Moderate
- WV:
- Low
- VA:
- Moderate
- MD:
- Low
- DE:
- Low
- AZ:
- Moderate
- NM:
- Moderate
- KS:
- High
- AR:
- High
- TN:
- High
- NC:
- High
- SC:
- High
- OK:
- High
- LA:
- Moderate
- MS:
- High
- AL:
- High
- GA:
- High
- TX:
- High
- FL:
- Moderate
- AK:
- Low
- HI:
- Low
What Johnson Grass Cross-Reacts With
Patients sensitized to one allergen often react to others sharing similar proteins. This map shows the documented molecular overlaps.
Johnson grass (Panicoideae) shares Sor h 1 Group 1 allergen cross-reactivity with bahia, Bermuda, and partially with temperate Pooideae grasses — but its Group 5 absence limits Pooideae cross-coverage to roughly 40%, leaving the majority of Sor h 1 sensitization untreated by Timothy-only SCIT.
Panicoideae — Sor h 1 shows ~70% IgE inhibition with Pas n 1 (Esch & Bush, 2008)
Panicoideae — Group 1 cross-reactivity inferred from subfamily classification
~55% Cyn d 1 inhibition with Sor h 1 (Johansen et al., 2009, Clin Exp Allergy)
Is SCIT Right for Your Johnson Grass Allergy?
Answer five questions to assess whether Johnson grass SCIT fits your Plains or Southeast allergy profile.
How severe are your late-summer grass or pollen allergy symptoms (July–September)?
The Johnson Grass SCIT Protocol
Johnson grass SCIT uses a non-standardized extract (ImmunoCAP g10 for Sorghum halepense) dosed in PNU or W/V, typically combined with bahia and Bermuda in a single warm-season vial separate from any Pooideae grass components. The Panicoideae/Chloridoideae warm-season mix ensures patients receive meaningful cross-coverage across the Gulf-Plains warm-grass complex.
Injections escalate from a highly dilute starting concentration to the target maintenance dose under the mandatory 30-minute post-injection observation period. Your allergist will titrate the PNU-based Johnson grass dose individually using skin endpoint titration or intradermal testing. Curex uses a conservative once-weekly build-up schedule and does not offer rush or cluster protocols.
Ongoing maintenance injections sustain immune tolerance through the summer pollen season. Because Johnson grass peaks later (July–September) than Bermuda and bahia, maintenance injections during the critical late-summer window are especially important for sustained tolerance. Annual assessment of symptom burden and medication use guides the decision to continue or taper.
Patients completing a full warm-season grass SCIT course typically experience sustained symptom reduction for years after stopping treatment. Agricultural patients with ongoing high occupational Johnson grass exposure may elect to continue maintenance indefinitely in consultation with their allergist.
Extract Concentration Ladder
You progress through each vial during build-up. Concentration increases ~10x per step.
What the Research Shows for Johnson Grass SCIT
No published double-blind placebo-controlled SCIT trial has used Johnson grass extract as its primary intervention. Efficacy is extrapolated from broader grass SCIT meta-analyses — an honest data gap explicitly acknowledged here.
- Grass SCIT symptom score reduction (meta-analysis)40%Calderón M et al., 2007, Cochrane Database Syst Rev — broad grass SCIT systematic review
- Plains/Southeast grass-allergic patients with Sor h 1 IgE45%Multiple regional series cited in Lo & Bush, 2009, Allergy Asthma Proc — 35–55% range
- IgE inhibition of Phl p 1 (Timothy) by Sor h 140%Andersson & Lidholm, 2003, Int Arch Allergy Immunol — cross-reactivity baseline
No Johnson-grass-specific SCIT RCT has been published as of 2024. The Calderón 2007 Cochrane review documents robust grass SCIT efficacy broadly, primarily from Pooideae studies. For Johnson grass, the most clinically relevant data are the 35–55% sensitization prevalence in Plains allergy clinics and the 40% Pooideae cross-inhibition ceiling — confirming that Timothy-only SCIT leaves the majority of Sor h 1 sensitization inadequately covered and that a dedicated Panicoideae vial is clinically justified.
Ready to skip the surprise bills?
At-home allergy shots (SCIT) are designed by board-certified allergists. See the listed SCIT plan rate in our pricing record and request a quote for eligibility, initiation and total care costs.
- MD-ledBoard-certified allergists
- QuoteTotal care estimate
- 50K+Patients treated
- HSA/FSAEligible
Johnson Grass SCIT Side Effects
Johnson grass SCIT carries the same local and systemic reaction profile as other inhalant SCIT extracts, managed through the mandatory 30-minute post-injection observation period.
Local reactions
4 documented| Reaction | Rate | Severity |
|---|---|---|
Injection-site swelling Wheal and flare at the injection arm; resolves within hours | Rate 30–50% | Mild |
Injection-site itching Pruritus at injection site; cold compress provides relief | Rate 25–40% | Mild |
Large local reaction (>25 mm) May require dose adjustment; inform your allergist before next injection | Rate 5–10% | Moderate |
Delayed local induration Firm lump at injection site persisting 24–48 hours; resolves without treatment | Rate 2–5% | Mild |
Systemic reactions
4 documented| Reaction | Rate | Severity |
|---|---|---|
Nasal/conjunctival flare Brief worsening of baseline allergy symptoms post-injection | Rate 0.5–1% | Mild |
Generalized urticaria Managed with antihistamines; dose reduction at next visit | Rate 0.1–0.3% | Moderate |
Mild bronchospasm More likely in patients with poorly controlled asthma — pre-treatment spirometry recommended | Rate 0.1–0.2% | Moderate |
Systemic anaphylaxis Managed with epinephrine; Curex confirms a prescribed auto-injector is on hand and supervises the first injection from each new vial or concentration live in the Virtual Shot Room | Rate <0.01% | Severe |
No deaths from inhalant SCIT have been reported in the US in the past decade under proper protocols. Non-standardized Johnson grass extract requires individualized dose titration — which is exactly why Curex keeps a board-certified allergist overseeing the plan, supervises the first injection from each new vial or concentration live in the Virtual Shot Room, and confirms a prescribed epinephrine auto-injector is on hand, making eligible at-home maintenance possible.
SCIT vs Alternatives for Johnson Grass
Plains and Southeast patients with Johnson grass sensitization have four management options: SCIT with a warm-season Panicoideae vial, at-home SLIT drops, avoidance, or daily symptom-control medications.
| Criterion | At-Home SCIT (Curex)Best | SLIT drops/tablets | Avoidance | Medications |
|---|---|---|---|---|
| Effectiveness | Disease-modifying; extrapolated 40%+ reduction (Calderón 2007) | Moderate — no FDA-approved Johnson grass SLIT; custom drops available | Minimal — pollen drifts 5–10 km from fields | Symptom suppression only |
| 5-yr cost | $3,500–$10,000 | $1,500–$4,000 | Low direct cost | $500–$3,000 |
| Duration | 3–5 years | 3–5 years | Ongoing | Indefinite daily use |
| Convenience | At-home self-injection; weekly build-up → monthly | Daily drops at home | High lifestyle burden | Easy — oral/nasal |
| Safety | <0.01% anaphylaxis; Virtual Shot Room–supervised dosing + prescribed epi | Very low systemic risk | Excellent | Generally safe; drowsiness risk |
| Lasting effect | 7–12+ years post-course | Moderate lasting effect | No disease modification | None — symptoms return off medication |
At-Home SCIT (Curex)Best
SLIT drops/tablets
Avoidance
Medications
SCIT with a dedicated Panicoideae warm-season vial — including Johnson grass alongside bahia — provides the most robust disease-modifying option for Plains and Southeast patients. Curex delivers that SCIT as an at-home allergy shot with pricing confirmed in a current program quote: a tailored multi-allergen serum that can include Sorghum halepense alongside concurrent weed or mold sensitizations, compounded under USP <797>, with the first injection from each new vial or concentration supervised live in the Virtual Shot Room, a prescribed epinephrine auto-injector confirmed on hand, and allergist-overseen escalation — so eligible rural and agricultural patients avoid weekly clinic trips.
What Johnson Grass SCIT Actually Costs
Most major US insurers cover grass pollen SCIT including non-standardized warm-season grasses like Johnson grass under standard allergy treatment benefits. Curex's at-home Sor h 1 IgE testing can document Johnson grass sensitization and geographic exposure for prior authorization without requiring an initial office visit. Rural and agricultural patients should confirm in-network allergist availability, as Plains allergy clinics may require additional travel.
Cost range varies by deductible, co-insurance, and clinic.
Verify these codes with your insurer to confirm coverage.
See the listed Environmental Allergy Shots Plan rate, commercial terms dated 2026-10-12; consultations are included without copay. Confirm availability, eligibility, other included services, testing, any in-person care, insurance responsibility and billing cadence in your written quote before enrolling.
Join the waitlistStop guessing about your johnson grass allergy. Get a plan.
Take Curex’s 3-minute allergy quiz. A board-certified allergist will review your symptoms and recommend the right immunotherapy path for you — shots or drops.
Free quiz · Board-certified allergists · 50,000+ patients treated · HSA/FSA eligible
Johnson Grass SCIT — Frequently Asked
Quick answers to the questions patients ask most before starting treatment.
Johnson grass and short ragweed are the two dominant late-summer agricultural pollen allergens across the Plains states, but they are fundamentally different plants. Johnson grass (Sorghum halepense) is a Poaceae grass whose major allergens (Sor h 1, Group 1 beta-expansin) cross-react with other grasses and can be covered by a warm-season grass SCIT vial. Short ragweed (Ambrosia artemisiifolia) is an Asteraceae weed whose major allergen (Amb a 1, pectate lyase) is immunologically unrelated to grass allergens and requires a separate SCIT formulation or the FDA-approved Ragwitek SLIT tablet. The two seasons overlap (Johnson grass peaks July–September, ragweed peaks August–October), and many Plains patients have dual sensitization, requiring concurrent grass and weed components in their SCIT regimen.
Johnson grass is the most molecularly characterized Panicoideae grass species, with five named allergens in the WHO/IUIS allergen nomenclature database (2024 update): Sor h 1 is the major Group 1 beta-expansin allergen, recognized by more than 85% of Johnson-grass-sensitized patients (Avjioglu et al., 1993, Clin Exp Allergy). Sor h 2 is a Group 2/3 expansin-like protein. Sor h 7 is a polcalcin — a pan-allergen cross-reactive across all pollen types. Sor h 13 and Sor h 23 are polygalacturonase-related proteins. The five-allergen characterization gives clinicians more component-resolved diagnostic options for Johnson grass than for any other warm-season grass, though most clinical testing relies on Sor h 1 (via ImmunoCAP g10) as the primary marker.
Johnson grass reaches 6–8 feet at maturity — significantly taller than most lawn grasses — and its tall canopy releases pollen at an altitude that enables long-range aerial transport. Atmospheric dispersion modeling by Aylor (2003, Journal of Aerosol Science) estimated that light grass pollen from tall canopy sources can travel 5–10 km under typical summer Plains wind conditions. This means suburban neighborhoods and small towns miles from agricultural infestations can experience significant Johnson grass pollen exposure during July–August without any nearby visible Johnson grass stands. The grass is also USDA-listed as a noxious weed in 19 states and has proved extremely difficult to eradicate from crop fields, meaning exposure burden is structurally persistent across the Plains agricultural landscape.
Johnson grass (Sorghum halepense) shares Panicoideae subfamily Group 1 cross-reactivity with both sugarcane (Saccharum officinarum) and corn pollen (Zea mays) at the beta-expansin level (Petersen et al., 2008, Mol Immunol). Johnson grass SCIT may provide partial cross-coverage for patients with concurrent Panicoideae sensitization. However, corn pollen allergy has its own distinct exposure context — primarily agricultural workers in Midwest corn-growing states — and there are no published clinical studies specifically validating Johnson grass SCIT as a substitute for corn-pollen-specific treatment in highly sensitized corn-field workers. Your allergist can assess whether corn pollen should be included as a separate extract component based on your documented exposure and sensitization profile.
Yes, and they are often the most symptomatic patients in Plains allergy clinics. Farmworkers who drive or operate machinery through Johnson grass-infested fields face direct, high-concentration pollen and plant-contact exposure during July–September that far exceeds suburban ambient levels. This occupational exposure pattern makes the 35–55% sensitization rate among Plains grass-allergic patients (Lo & Bush, 2009) an underestimate for agricultural worker subgroups. SCIT with a warm-season Panicoideae vial is the most appropriate disease-modifying intervention, as avoidance is functionally impossible for farmers working infested land. Cluster build-up protocols are particularly useful for agricultural patients who need to reach maintenance before the July pollen peak and who may have irregular access to clinic appointments during harvest seasons.
Most major US health insurers cover grass pollen SCIT under standard allergy treatment benefits, including non-standardized warm-season extracts like Johnson grass. Coverage requires documented IgE sensitization (positive skin prick test or serum Sor h 1 IgE), prescription by a board-certified allergist, and prior authorization. Because Sorghum halepense extract is non-standardized, the authorization letter should document geographic exposure (agricultural county with documented Johnson grass infestation) and sensitization testing results. CPT codes 95115, 95117, and 95165 apply. Rural Plains patients should confirm that their insurer has an in-network allergist in their geographic area before beginning treatment planning.
This is a clinically common diagnostic challenge in Plains states because both Johnson grass (July–September peak) and short ragweed (August–October peak) cause late-summer symptoms with similar presentation — sneezing, rhinorrhea, itchy eyes, and potential asthma involvement. A key diagnostic clue is the relative timing: if symptoms are severe in July before the ragweed season begins, or if symptoms persist well past November when grasses have stopped, the primary driver may differ from the initial assumption. Component-resolved testing is the gold-standard solution: high Sor h 1 IgE confirms Johnson grass sensitization, while high Amb a 1 IgE confirms ragweed. Many Plains patients have dual sensitization requiring both a warm-season grass vial and a separate ragweed component in their SCIT regimen.
No FDA-approved SLIT tablet covers Johnson grass — Grastek (Timothy) and Oralair (5-grass mix) contain only Pooideae species and provide minimal cross-coverage for Sor h 1 sensitization. Custom sublingual immunotherapy drops can be formulated to include Sorghum halepense extract, but published head-to-head comparison data between Johnson grass SLIT and SCIT are not available. The broader grass SLIT versus SCIT literature suggests SCIT typically achieves larger effect sizes, particularly for highly sensitized patients with severe symptoms. For rural Plains patients where clinic access is difficult, Curex's at-home allergy shot delivers that higher-effect-size SCIT with Virtual Shot Room–supervised dosing and a prescribed epinephrine auto-injector confirmed on hand — no regular clinic trips needed. A large safety study of self-administered allergen immunotherapy (Schaffer et al., 2015) supports this delivery model, finding that across 23,614 patients giving 2,021,600 injections the systemic reaction rate was just 0.16% per patient with no fatalities — lower than the 3%–14% typically seen with office-based shots. A board-certified allergist guides the decision based on sensitization level and symptom severity.
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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