Are allergy drops safe? Results from 18,398 patient-years of Curex patients
Curex’s second peer-reviewed study tracked every reported side effect in 13,584 patients treating their allergies at home with sublingual drops. Here is what it found, and how Curex keeps home treatment safe.
For most people with environmental allergies, yes. In the 2026 peer-reviewed study of 13,584 Curex patients and 18,398 patient-years of at-home sublingual immunotherapy, side effects were predominantly mild, mostly nasal congestion, sneezing or throat irritation. There were no deaths. Anaphylaxis or a severe allergic reaction was reported by 2 of 13,584 patients, and only 1 was judged treatment-related. By 36 months, 1.8% of patients had stopped because of side effects. The authors concluded that SLIT may be administered and monitored fully at home through telemedicine with low rates of reported serious adverse events (Allergy, Asthma & Clinical Immunology, 2026). Home treatment is not for everyone: pregnancy, uncontrolled asthma and active eosinophilic esophagitis rule it out, and anyone with a history of anaphylaxis should be seen in person first.
Written by Dr. Chet Tharpe, MD · Medically reviewed by Dr. Neeta Ogden, MD, FACAAI · Last reviewed October 2026
The study at a glance
Home treatment since 2020, in numbers
Curex’s second peer-reviewed paper, published October 21, 2026 in Allergy, Asthma & Clinical Immunology (BMC / Springer Nature), reviewed every reported side effect among Curex patients treated with personalized sublingual immunotherapy (SLIT) at home from November 2020 to May 2026. Read the full paper.
- Curex patients included, from 29,675 who received at least one shipment
- 13,584Curex patients included, from 29,675 who received at least one shipment
- patient-years of home treatment, adjusted for how consistently patients took their drops
- 18,398patient-years of home treatment, adjusted for how consistently patients took their drops
- deaths
- 0deaths
- stopped treatment because of side effects by 36 months
- 1.8%stopped treatment because of side effects by 36 months
Tharpe C et al. Allergy Asthma Clin Immunol. 2026. doi:10.1186/s13223-026-01079-1. Open access, CC BY 4.0.
Who was in the study
| Measure | Result |
|---|---|
| Patients included | 13,584 (45.8% of the 29,675 who received at least one shipment; 144,972 shipments in all) |
| Inclusion | At least one shipment and at least one completed quarterly follow-up survey |
| Treated for | Environmental allergies, all patients; 113 (0.83%) also received food-allergy drops |
| Age and sex | Mean age 38.3 years; 52.8% women |
| Other conditions | Reflux (GERD) 22.1%, asthma 12.8%, eczema 0.9%, a prior eosinophilic esophagitis diagnosis 0.8% (112 patients) |
| Allergens per formula | Median 10 (up to 26); most often cat (73.2%), dust mites (73.1%) and dog (68.6%) |
| Time on treatment | Median 17.1 months, up to 59 months; 67.8% treated for more than a year and 28.3% for more than two |
| Confirmed allergy | 95.7% had IgE sensitization confirmed by testing |
Side effects were graded with the National Cancer Institute’s CTCAE v5.0 scale from the quarterly surveys sent with every shipment. Serious events were reviewed by Curex clinicians, and possible anaphylaxis was assessed against NIAID/FAAN criteria.
Results
Side effects by severity grade
Grade I is mild, Grade II moderate, Grade III severe, Grade IV life-threatening and Grade V death. A patient who reported events of different grades is counted in each.
| Grade | Patients reporting at least one event | Events per 100 patient-years |
|---|---|---|
| Grade I — mild | 1,054 (7.76%) | 6.37 |
| Grade II — moderate | 265 (1.95%) | 1.56 |
| Grade III — severe | 12 (0.09%) | 0.07 |
| Grade IV — life-threatening | 1 (0.01%), unrelated to treatment | 0.005 |
| Grade V — death | None | — |
| All grades | — | 8 (95% CI 7.60–8.42) |
The single Grade IV event was a cardiac arrest in a patient with a pre-existing heart-rhythm disorder; it was judged unrelated to the drops, and treatment continued. Grade II and III rates stayed low in every calendar year (Grade II 1.0–2.7%, Grade III 0.0–0.2%).
The most common side effects
The side effects patients reported most often were upper-respiratory and mostly mild — the kind of symptoms allergies themselves cause.
| Side effect | Grade I (mild) | Grade II (moderate) |
|---|---|---|
| Nasal congestion | 1.07% | 0.29% |
| Sneezing | 0.71% | 0.15% |
| Throat irritation | 0.57% | 0.09% |
| Runny nose or post-nasal drip | 0.53% | 0.14% |
| Cough | 0.46% | 0.18% |
| Mouth swelling | 0.44% | 0.04% (Grade III 0.01%) |
| Mouth itching or tingling | 0.35% | 0.07% |
Percentages are the share of all 13,584 patients who reported the side effect at that grade at least once.
Serious reactions
Anaphylaxis, angioedema and EoE: what happened
- Anaphylaxis or a severe allergic reaction: 2 patients (0.01%). Both were Grade III, both in patients treated for environmental allergies (0.011 per 100 patient-years). One was treatment-related: it came after two years of treatment, when new allergens were added to the formula, and the prescriber stopped treatment. The other was judged unlikely to be related — no trigger was found, and the patient continued drops without another reaction.
- Generalized angioedema: 3 patients (0.02%). Widespread swelling was reported three times across the whole cohort, one of them Grade III.
- New eosinophilic esophagitis (EoE): 5 patients (0.04%). Five confirmed or suspected new cases, two of them suspected by gastroenterologists to be related to the drops; both resolved or stopped treatment.
- Existing EoE: 3 flare-ups among 112 patients. Of 112 patients who started drops with a prior EoE diagnosis, three reported a flare-up (0.02% of the cohort). The drops were judged an unlikely cause in all three, and treatment continued under close monitoring.
Why patients stopped
Over the whole study, side effects were the reason for stopping in only 1.4% of patients. The reasons patients gave most often were cost (14.5%), losing interest or not noticing enough benefit (11.2%) and access barriers (8.2%); 4.5% stopped because they had completed treatment.
Measured over time, 1.1% of included patients had stopped because of side effects by 12 months, 1.5% by 24 months and 1.8% by 36 months.
The care model
How Curex keeps home treatment safe
The paper describes the care model behind these results. How Curex works covers the full treatment path.
- Screening before the first dose. A detailed medical-history intake checks for conditions that rule out home treatment — pregnancy, uncontrolled asthma, active eosinophilic esophagitis — and for other health problems.
- A US board-certified allergy clinician. Every patient consults a board-certified allergy clinician by text, phone or video, including a 10-point review of systems at the video consultation.
- Confirmed allergies. 95.7% of patients in the study had IgE sensitization confirmed by testing — from earlier lab results or an ImmunoCAP blood test arranged by Curex.
- A gentle start. Drops build up at a 1:5 dilution before moving to the 1:1 maintenance strength; food-allergy drops start far more dilute and build up more slowly.
- Early and regular follow-up. A follow-up video consultation within 1–2 weeks of starting, and a structured symptom survey with every quarterly shipment.
- Same-business-day answers. Clinicians respond the same business day, typically immediately or within a few hours.
- Epinephrine and an emergency plan. An epinephrine auto-injector is offered to every new patient and required for food-allergy drops. The first shipment includes a safety manual covering anaphylaxis symptoms, how to use epinephrine and when to call 911.
- Swallowing problems mean an immediate pause. Any trouble swallowing or food sticking stops dosing straight away and leads to a gastroenterologist referral.
Know the signs
Anaphylaxis and EoE, explained plainly
Anaphylaxis is a sudden, severe allergic reaction that affects breathing, circulation or more than one part of the body at once. With allergy drops it is rare — 2 reports among 13,584 Curex patients — but every patient should know the signs: throat tightness, a hoarse voice or trouble swallowing; wheezing or shortness of breath; lightheadedness or fainting; swelling of the tongue or lips together with another symptom; or widespread hives with vomiting or breathing symptoms.
What to do: use your epinephrine auto-injector in the outer thigh straight away, then call 911. Antihistamines and inhalers do not treat anaphylaxis. Do not take another dose until you have spoken to your Curex clinician.
Eosinophilic esophagitis (EoE) is inflammation of the esophagus, the tube that carries food to the stomach. It can cause trouble swallowing, food that feels stuck, heartburn or chest pain that keeps coming back. In the study, 5 of 13,584 patients had confirmed or suspected new EoE.
What to do: stop your drops and message your Curex clinician. Curex pauses treatment and refers you to a gastroenterologist.
For everyday reactions — an itchy mouth in the first weeks, when to hold a dose — see allergy drops side effects and when to get help.
Before you start
Who should not start allergy drops at home
- Pregnancy. Immunotherapy is not started during pregnancy. If you become pregnant during treatment, tell your clinician straight away.
- Uncontrolled or severe asthma. Asthma needs to be under control first; an in-person evaluation comes before any immunotherapy.
- Active eosinophilic esophagitis. Active EoE rules out starting drops; a past diagnosis needs a careful review with your clinicians.
- A history of anaphylaxis. Start with an in-person allergist evaluation.
- A past severe reaction to immunotherapy. Any severe reaction to shots, tablets or drops needs specialist review first.
- Beta-blockers or significant heart disease. Tell your clinician; these need a careful review before any immunotherapy.
About the study
This is Curex’s second peer-reviewed study. The first, published in Frontiers in Allergy in June 2026, followed 2,897 adults treated with Curex environmental-allergy drops and reported improving symptoms, quality of life and adherence over two years (PMID 42358593). Both studies are summarized on Curex by the numbers.
The authors note that side effects were self-reported through quarterly surveys without outside verification, that the analysis included patients who completed at least one survey, that some reported symptoms overlap with allergy symptoms themselves, and that the data come from one telemedicine platform; they call for randomized trials comparing remote and in-person care.
The study was funded by Curex; statistical analysis was performed independently by Arx Sciartis.
Citation
How to cite this study
Tharpe C, Mardaga K, Davidson J, Solow C, Kakaulin G, Kruzick T, Herold J, Snyder M, Hakobyan B. Real-world safety of personalized telemedicine-delivered sublingual immunotherapy: reported adverse events across 18,398 patient-years. Allergy Asthma Clin Immunol. 2026. doi:10.1186/s13223-026-01079-1. Published online October 21, 2026 (Article in Press). Open access under a CC BY 4.0 license.
Frequently Asked Questions
For most people with environmental allergies, yes. In Curex’s 2026 peer-reviewed study of 13,584 patients and 18,398 patient-years of home treatment, side effects were predominantly mild: 7.76% reported a mild (Grade I) event, 1.95% a moderate (Grade II) event and 0.09% a severe (Grade III) event, and there were no deaths. A clinician should confirm that drops are right for you first.
The most common are mild and allergy-like: nasal congestion (1.07% mild), sneezing (0.71%), throat irritation (0.57%), a runny nose (0.53%), cough (0.46%), mouth swelling (0.44%) and mouth itching or tingling (0.35%) in the Curex study. Itching in the mouth is most common in the first weeks of treatment.
The study authors concluded that SLIT may be administered and monitored fully at home through telemedicine with low rates of reported serious adverse events. Curex screens every patient before the first dose, starts at a diluted strength, follows up by video within 1–2 weeks, surveys symptoms with every shipment, answers the same business day and offers every new patient an epinephrine auto-injector.
Rarely. Among 13,584 Curex patients, 2 reported anaphylaxis or a severe allergic reaction, and 1 was judged treatment-related. Know the signs — throat tightness, trouble breathing, fainting or widespread hives after a dose — and use epinephrine and call 911 if they appear.
It is rare. Five of 13,584 Curex patients (0.04%) developed confirmed or suspected new EoE, two of them suspected to be related to the drops. Trouble swallowing or food sticking means stopping your drops and contacting your clinician; Curex refers you to a gastroenterologist.
Few. Side effects were the reason for stopping in 1.4% of Curex patients in the study; by 36 months, 1.8% had stopped because of side effects. Cost and losing interest were far more common reasons.
Do not start during pregnancy, with uncontrolled or severe asthma, or with active eosinophilic esophagitis. Anyone with a history of anaphylaxis or a past severe reaction to immunotherapy should be evaluated by an allergist in person first.
If you experience sudden difficulty breathing, throat swelling, or other signs of anaphylaxis, call 911. A prescribed epinephrine auto-injector is the first-line treatment — not antihistamines.
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.
Sources
Where the facts come from
Sources
- Tharpe C et al. Real-world safety of personalized telemedicine-delivered sublingual immunotherapy: reported adverse events across 18,398 patient-years. Allergy Asthma Clin Immunol 2026 (doi:10.1186/s13223-026-01079-1)
- Tharpe C et al. Front Allergy 2026 — 2,897-patient telemedicine SLIT outcomes cohort (PMID 42358593)
- Allergy drops side effects: what is normal, when to stop, when to call 911
- Curex by the numbers: both peer-reviewed studies
Keep reading
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- Is Curex legit?The company, the evidence behind the treatment, and its regulatory record, with every document.Read
- Curex and the FDATwo separate matters: the 2021 allergy-drops questions and the 2025–2026 GLP-1 marketing letters, with what Curex changed.Read
- How Curex worksThe treatment process end to end, from at-home testing to daily drops.Read
- Curex reviewsWhat patients actually report — both clusters, including the complaints.Read
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