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.
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
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 statesWhat 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. Cluster build-up protocols (8 visits to maintenance) are an option for motivated Plains patients who face long drives to allergy clinics.
Monthly 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?
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- 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 documentedSystemic reactions
4 documentedNo 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 dose and every dose change live over Zoom, 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; Zoom-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 at $129/month: a tailored multi-allergen serum that can include Sorghum halepense alongside concurrent weed or mold sensitizations, compounded under USP <797>, with the first dose and every dose change supervised live over Zoom, 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.
Flat monthly subscription — includes consult, prescription, and at-home dosing for sublingual immunotherapy.
See if you qualifyStop 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.
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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.
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.