Ragweed (Ambrosia artemisiifolia L.): Botanical Identity, Traditional Use, Phytochemistry, and Clinical Evidence
1. Identity and Botanical Characterization
Taxonomy and Nomenclature
Ambrosia artemisiifolia, with the common names common ragweed, annual ragweed, and low ragweed, is a species of the genus Ambrosia native to regions of the Americas. The species name, artemisiifolia, is given because the leaves were thought to bear a resemblance to the leaves of Artemisia, the true wormwoods. It has also been called the common names: American wormwood, bitterweed, blackweed, carrot weed, hay fever weed, Roman wormwood, short ragweed, stammerwort, stickweed, and tassel weed.
Ragweed is a summer annual noxious weed in the daisy family (Asteraceae) and is native to most of North America but has naturalized in many parts of the world. The genus name is Greek for "food of the gods" or "drink of immortality." Originating in North America, the plant genus Ambrosia has become a very significant invasive species globally, capable of producing vast quantities of highly allergenic pollen. The genus includes around 50 species and poses considerable health risks due to its pollen, which is a major cause of allergic rhinitis.
The two most medicinally and allergologically studied species within the genus are Ambrosia artemisiifolia L. (common or short ragweed) and Ambrosia trifida, the giant ragweed, a species of flowering plant in the family Asteraceae native to North America, where it is widespread in Canada, the United States, and northern Mexico. This article focuses primarily on A. artemisiifolia, except where noted.
Morphology and Distribution
Ambrosia artemisiifolia is an annual plant that emerges in late spring. It propagates by seed. It is much-branched and grows up to 70 centimetres (2.3 ft) in height. The pinnately divided soft and hairy leaves are 3β12 centimetres (1.2β4.7 in) long. Its bloom period is July to October in North America. Its pollen is wind-dispersed and can be a strong allergen to people with hay fever.
The plant is native to: North America across Canada, the eastern and central United States, the Great Plains, and in Alaska; the Caribbean on Cuba, Hispaniola, and Jamaica; and South America in the southern bioregion (Argentina, Chile, Paraguay, Uruguay), the western bioregion (Bolivia, Peru), and Brazil. The distribution of common ragweed in Europe is expected to expand northwards in the future due to climate change.
Common Forms and Preparations
In the context of dietary supplement and herbal use, ragweed has been prepared in several forms. Preparations from leaves and roots have served as an astringent, antiseptic, emetic, and febrifuge. Teas and tinctures have been used for fevers, nausea, intestinal cramps, diarrhea, and menstrual discomfort. Externally, poultices from crushed leaves have been used to soothe skin irritations, insect bites, poison ivy rashes, and rheumatic joints. In contemporary Europe, the herb has emerged in commercial form as a food-grade puree (typically young plant material in olive oil), as well as in teas and encapsulated extracts, though standardized preparations remain outside established pharmacopoeial or monograph systems.
In a wholly distinct medical context β allergen immunotherapy β RAGWITEKβ’ (Short Ragweed Pollen Allergen Extract) Tablet for Sublingual Use (12 Amb a 1-U) is an allergen extract indicated as immunotherapy for the treatment of short ragweed pollen-induced allergic rhinitis with or without conjunctivitis confirmed by positive skin test or in vitro testing for pollen-specific IgE antibodies for short ragweed pollen. This is a prescription pharmaceutical, not a dietary supplement.
2. Traditional and Historical Use
Native American Traditions
Ambrosia artemisiifolia has been a traditional medicinal plant for Native American tribes, including the Cherokee, Lakota, Iroquois, Dakota, and Delaware. Historically, A. artemisiifolia was used by the Otoe Native American tribe in the Missouri River region as a remedy for nausea.
The Iroquois and the Dakota compounded a decoction of the leaves and the top part of the plant to treat diarrhea, and an infusion of the roots was used as a heart medicine. The Lakota made an infusion of the leaves and used it to treat swelling. The Houma used a decoction of this root for menstrual trouble.
Ethnobotanical sources mention certain use of A. artemisiifolia by Native Americans for medicinal purposes β for example, to treat insect bites, infected toes, minor skin eruptions, and hives, and tea used for fever and nausea. The medicinally used parts were the leaves and herbs. However, there are no detailed data on the developmental stages of the utilized plants.
For Ambrosia trifida (giant ragweed), traditional use is also documented: the Cherokee used it as a remedy for insect stings, hives, fever, and pneumonia, and the Iroquois used it to treat diarrhea. The plant is suspected to have been domesticated by Native Americans as an oily seed crop as early as 1200 BCE.
Seeds of Ambrosia trifida have been found at archaeological sites, leading to the belief that giant ragweed was used as a medicine or even a source of food that may have been cultivated specifically for food and fiber.
Eclectic and Early American Medical Traditions
Ambrosia artemisiifolia was a traditional medicinal plant for many Native American tribes, including the Cherokee. Early American physicians also recognized ragweed's medicinal uses as a topical and internal remedy.
Ragweed is most well-known in eclectic herbalism for its astringent qualities, and became popular for hay fever, which is mostly described as itchy, watery, bloodshot eyes, sore throat, and itchy, runny nose. It seems to work well in any case of excessive discharge where the mucus is clear, slightly yellow, and watery. King's American Dispensatory (1898) mentions its use for leucorrhea and also for watery discharge from the urethra. It is also mentioned in excessive cases of salivation from mercurial poisoning. It also has a use topically as a styptic and antiseptic for recent wounds, tumors, or ulcers.
The medicinal use of the herb has started recently in Europe, even though common ragweed had never been part of European folk medicine.
3. Key Constituents and Active Compounds
Overview
A comprehensive study of the chemical constituents of Ambrosia revealed 295 compounds. The diverse constituents predominantly include sesquiterpenoids, flavonoids, terpenoids, steroids, and coumarins. Plant species of this genus exhibit a wide range of biological activities, including molluscicidal, antitumor, antimycobacterial, antiproliferative, antioxidant, antiherbivore, and allelopathic properties.
Sesquiterpene Lactones
To date, 60 sesquiterpene lactones have been isolated from A. artemisiifolia, and most reports have described the guaiane, pseudoguaiane, seco-pseudoguaiane, germacrane, daucane, and eudesmane sesquiterpene backbones in samples of different geographical origins. In addition to primary bioactivities (cytotoxic and antiproliferative activity), these specialized metabolites also have other notable pharmacological activities, such as antibacterial, antifungal, anti-inflammatory, and antiprotozoal effects.
Among the identified sesquiterpene lactones are: psilostachyin, psilostachyin B, and psilostachyin C, which were isolated from the aerial parts of Ambrosia artemisiifolia. Other named compounds include ambrosin, cumanin, ambrosic acid, artesovin, and related lactones. A more recently characterized compound, isabelin, a sesquiterpene dilactone, has been discovered in this plant, and its bioactivity has been demonstrated on allergy-related receptors.
Most of the Ambrosia sesquiterpenes possess a C-11/C-13 exocyclic double bond conjugated to the Ξ³-lactone, which provides characteristic bioactivities to these secondary metabolites such as antiproliferative, cytotoxic, and anti-inflammatory activities.
Sesquiterpene lactone content is not static: the sesquiterpene lactone content can vary over time and in the different vegetation periods of the plant. Sesquiterpene lactone production in plant samples peaked at the end of July or in August; the trend of the change in sesquiterpene lactones may correlate with precipitation and temperature. Geographical location and geoclimatic factors might exert significant influence on the production of sesquiterpene lactones in ragweed.
Pollen Allergens
Ragweed pollen is a major endemic allergen source responsible for severe allergic manifestations in IgE-sensitized allergic patients. It contains the major allergen Amb a 1 and cross-reactive allergen molecules, such as the cytoskeletal protein profilin (Amb a 8) and calcium-binding allergens Amb a 9 and Amb a 10.
Amb a 1 is the major allergen, inducing IgE sensitization in more than 90% of ragweed pollen-sensitized individuals. Amb a 1-specific IgE accounts for more than 50% of ragweed pollen-specific IgE levels in the majority of ragweed pollen-allergic patients. Amb a 1 is a member of the pectate lyases that catalyze the breakdown of pectin (the major plant cellular wall component).
So far 11 ragweed allergens have been described and, according to IgE reactivity, Amb a 1 and Amb a 11 seem to be major allergens. Sensitization rates of the other allergens vary between 10 and 50%. Ragweed cross-reacts with mugwort (Artemisia vulgaris) and a correct diagnosis is only feasible with the ragweed-specific allergen Amb a 1. Due to cross-reactivity with mugwort, new sensitizations against ragweed pollen are not needed to evoke allergic symptoms.
Flavonoids and Other Constituents
Ragweed also contains antioxidant-type compounds including phenolic compounds and flavonoids that may contribute to laboratory anti-inflammatory or free-radical-scavenging effects. These are considered supportive rather than defining compounds. Some studies of ragweed essential oil and extracts have found antimicrobial or phytotoxic effects. These findings are more relevant to plant chemistry and agricultural or experimental uses than to household herbal use.
4. Scientific Evidence by Area of Use
4.1 Allergen Immunotherapy for Allergic Rhinoconjunctivitis
The most extensively studied and clinically validated use of ragweed as a therapeutic agent is in the form of standardized allergen immunotherapy β particularly sublingual immunotherapy tablets (SLIT-tablet) containing measured doses of Ambrosia artemisiifolia pollen extract, standardized in Amb a 1 units. This is the only use of ragweed for which robust, regulatory-grade evidence exists.
Regulatory status: RAGWITEK (Short Ragweed Pollen Allergen Extract, Ambrosia artemisiifolia) is indicated as immunotherapy for the treatment of short ragweed pollen-induced allergic rhinitis, with or without conjunctivitis, confirmed by positive skin test or in vitro testing for pollen-specific IgE antibodies for short ragweed pollen.
Pivotal clinical trials (Adults): The efficacy of RAGWITEK in the treatment of ragweed pollen-induced allergic rhinitis, with or without conjunctivitis, was investigated in two double-blind, placebo-controlled clinical trials in adults 18 through 50 years of age. In 4 placebo-controlled clinical trials, 1,057 subjects 18 years of age and older with short ragweed pollen-induced rhinitis, with or without conjunctivitis, received at least one dose of RAGWITEK. Of the subjects treated with RAGWITEK, 52% were male, 25% had mild asthma, and 82% were sensitized to other allergens in addition to ragweed pollen.
Pediatric evidence: A trial (NCT02478398) was conducted in North American and European children/adolescents ages 5β17 years with ragweed pollen-induced allergic rhinitis/conjunctivitis with or without asthma (FEVβ β₯ 80% predicted). Participants were randomized to daily ragweed SLIT-tablet (12 Amb a 1-U) or placebo for up to 28 weeks. The primary endpoint was the average total combined score (TCS; sum of rhinoconjunctivitis daily symptom score and daily medication score) during peak ragweed pollen season. The efficacy and tolerability of the ragweed SLIT-tablet in Canadian participants was consistent with the full study population that included participants from North America and Europe, with a 40.8% improvement in the TCS over placebo during the peak ragweed pollen season, despite the allowed use of symptom-relieving rescue medications.
Systematic review and meta-analysis: Ragweed allergen causes allergic rhinoconjunctivitis, and sublingual immunotherapy is one of the treatment modalities to desensitize allergic individuals. A systematic review assessed the effectiveness and safety of sublingual immunotherapy for allergic rhinoconjunctivitis caused by ragweed. Searches were performed through December 2020. English-language randomized controlled trials were included if they compared sublingual immunotherapy with placebo, pharmacotherapy, or other sublingual immunotherapy regimens, and reported clinical outcomes. The strength of the evidence was graded based on risk of bias, consistency, magnitude of effect, and directness of the evidence.
Quality of life outcomes: The efficacy and safety of standardized quality (SQ) sublingual immunotherapy (SLIT) tablets have been confirmed across large clinical trials in adults with grass, tree, ragweed, and house dust mite allergic rhinitis with or without conjunctivitis. A pooled analysis investigated whether the reduction in symptom burden found across the clinical trials is supported by improvements in quality of life. A total of 11 phase II/III randomized placebo-controlled trials across the SQ grass, tree, ragweed, and HDM SLIT tablets were included (ragweed: N = 767).
Real-world evidence: A review evaluating data from over 12,000 children, adolescents, and adults in non-interventional studies assessed the real-life effectiveness and safety of SQ sublingual immunotherapy tablets for allergic rhinitis. Non-interventional studies of SQ grass, tree, ragweed, and house dust mite SLIT tablets were identified from PubMed (January 2006 to February 2025). Effectiveness was captured as patient-reported change in AR symptoms, medication use, safety, and treatment satisfaction. In total, 12,136 participants were enrolled across 22 SQ SLIT tablet studies (ragweed: n = 102).
Persistence of effect: Disease-modifying effects of sublingual pollen tablet immunotherapy were confirmed in a 5-year trial, in agreement with previous long-term trials, where 3-year treatment resulted in long-term clinical efficacy that persisted for at least 2 years after the discontinuation of treatment.
Evidence strength summary: Evidence for ragweed SLIT-tablet for allergic rhinoconjunctivitis is strong β supported by multiple large, double-blind, placebo-controlled randomized trials, a systematic review, regulatory approval by the U.S. FDA, and real-world studies. This is the most robustly evidenced application of any ragweed-derived preparation.
4.2 Antiproliferative and Cytotoxic Activity (Preclinical Only)
Ambrosia artemisiifolia L. (Asteraceae) contains sesquiterpene lactones as characteristic secondary metabolites. Many of these compounds exert antiproliferative and cytotoxic effects. Research has investigated the isolation of sesquiterpene lactones from the aerial parts of A. artemisiifolia and elucidation of their cytotoxic, antiproliferative, and antibacterial effects.
In a published 2022 study, acetoxydihydrodamsin, 1β²-noraltamisin, and psilostachyin showed the most remarkable cytotoxic and antiproliferative activity on tumor cell lines and exerted selectivity towards the MRC-5 cell line.
Earlier work identified that sesquiterpene lactones psilostachyins A and C, isolated from the common ragweed Ambrosia artemisiifolia, modulated the G2 cell cycle checkpoint, as reported in Planta Medica.
Evidence strength summary: All anticancer/antiproliferative evidence is preclinical β limited to cell line (in vitro) assays and animal models. No human clinical trials have been conducted on ragweed extracts or isolated sesquiterpene lactones for oncological applications. These findings cannot be extrapolated to human health benefits.
4.3 Antimicrobial Activity (Preclinical Only)
This species produces a broad range of sesquiterpenoids. A recently discovered bioactive molecule, isabelin (a sesquiterpene dilactone), has been demonstrated to act on allergy-related receptors. Isabelin was tested for potential antimicrobial effects using a selection of soil-borne bacteria and fungi and three human pathogens as model organisms. For the majority of microorganisms tested, no antimicrobial activity of isabelin was observed; however, isabelin revealed strong antimicrobial activity against the Gram-positive soil bacterium Paenibacillus sp.
Evidence strength summary: Antimicrobial evidence is preliminary and in vitro only. Results are inconsistent across tested organisms and have not been validated in humans.
4.4 Traditional Indications (Fever, Digestion, Topical Wound Care): No Clinical Evidence
The traditional uses of ragweed β including as a febrifuge, astringent, antidiarrheal, emetic, and topical wound dressing β were employed across multiple Native American nations and early American eclectic physicians. However, these uses are documented only in ethnobotanical and historical sources. In herbal and phytochemical research, ragweed attracts interest because it contains bitter sesquiterpene lactones and other plant compounds with measurable biological activity in laboratory studies. No controlled human clinical trials have been conducted to evaluate ragweed preparations for any of these traditional indications.
5. Body Systems and Health Areas Associated with Ragweed
- Immune system / Respiratory system: Ragweed is one of the most important allergen sources worldwide, causing severe respiratory allergic reactions in late summer and fall in sensitized patients. In its immunotherapy form, it is specifically used to train and desensitize the immune system in allergic rhinitis.
- Dermatological system: Ragweed belongs to the sesquiterpenoid plants, which may contain phyto-contact allergens. In direct contact with plant parts like leaves, it may induce eczema on the hands, underarms, and face (especially eyelids) with papulo-vesicles, but also chronic hyperkeratotic eczema. Conversely, traditional use of crushed leaves as a poultice for minor skin wounds and insect bites was documented ethnobotanically.
- Gastrointestinal system: Traditional preparations (teas, decoctions) were directed at nausea, diarrhea, and intestinal complaints in Native American traditions.
- Oncology (preclinical interest only): Isolated sesquiterpene lactones from ragweed have shown cytotoxicity and antiproliferative effects in cell lines. No human data are available.
- Oral allergy syndrome: About every second adult with a ragweed allergy also suffers from oral allergy syndrome.
6. Dosage Forms and Reported Dosages
No standardized herbal dosing has been established by any pharmacopoeial body or regulatory authority for ragweed dietary supplement preparations. The following dosages are drawn only from specific sources, as reported:
Allergen Immunotherapy (RAGWITEK β Prescription Only)
RAGWITEK is an allergen extract indicated as immunotherapy for the treatment of short ragweed pollen-induced allergic rhinitis, with or without conjunctivitis. It is approved for use in persons 5 through 65 years of age. For sublingual use only. One tablet daily. Treatment should be initiated at least 12 weeks before the expected onset of ragweed pollen season and continued throughout the season.
RAGWITEK is available as a tablet of 12 Amb a 1-U of short ragweed pollen allergen extract. Inactive ingredients include gelatin NF (fish source), mannitol USP, and sodium hydroxide NF.
In the pediatric clinical trial referenced above, participants were randomized to daily ragweed SLIT-tablet (12 Amb a 1-U) or placebo for up to 28 weeks.
The pooled Canadian adult trial used ragweed sublingual tablet (SLIT-T; 6 and 12 Amb a 1-U of Ambrosia artemisiifolia) in patients aged β₯18 years with ragweed-induced allergic rhinoconjunctivitis with or without asthma.
Animal Toxicology Studies (Not a Therapeutic Dose)
In the sole published repeated-dose animal toxicology study, ragweed puree was administered in low dose (500 mg/kg b.w.) and high dose (1,000 mg/kg b.w.) to male Wistar rats according to 407 OECD Guidelines for the Testing of Chemicals. These are research doses used to assess toxicity and do not represent a human therapeutic dosage.
7. Safety Considerations and Interactions
Allergic and Anaphylactic Reactions (Pollen)
Ragweed pollen is known for its high potential to cause type I allergic reactions in late summer and autumn and represents a major health problem in America and several countries in Europe. The major allergens of the pollen are peptides with immunoglobulin-E binding capacity (Amb a 1 and Amb a 2 endopeptidases); they trigger rhinitis, oculorhinitis, and other symptoms of hay fever.
For the prescription sublingual tablet RAGWITEK, the prescribing information includes a boxed warning regarding severe allergic reactions. RAGWITEK is contraindicated in patients with severe, unstable, or uncontrolled asthma; a history of any severe systemic allergic reaction; a history of difficulty breathing due to swelling of the throat or upper airway after using any sublingual immunotherapy; a diagnosis of eosinophilic esophagitis; or allergy to any inactive ingredients contained in the product.
The first dose of RAGWITEK must be administered under the supervision of a physician with experience in the diagnosis and treatment of allergic diseases. Patients should be observed in the office for at least 30 minutes following the initial dose.
Contact Dermatitis
Dermal exposure to the plant can cause contact dermatitis, which has previously been described also for other plants belonging to Asteraceae. This reaction is due to the sesquiterpene lactones. Patch-test studies have confirmed that individuals sensitized to the sesquiterpene lactone mix in general may react to ragweed plant material specifically.
Oral Allergy Syndrome
About every second adult with a ragweed allergy also suffers from oral allergy syndrome. This cross-reactive response can manifest as itching or swelling of the mouth and throat upon ingestion of certain raw fruits, vegetables, or seeds, including some that are cross-reactive with ragweed pollen proteins.
Internal Toxicology Concerns
The herb of A. artemisiifolia has recently gained popularity as a medicinal plant and food. The effects of its long-term intake are unknown; there are no toxicological data to support the safe use of this plant.
In a rat model, reduced liver function enzymes (AST, ALT) and reduced triglyceride levels were observed in the low-dose group, and increased carbamide levels were seen in the high-dose group. The weight of the liver relative to body weight was significantly reduced in both groups, while the brain weight relative to body weight was significantly elevated in both groups. According to the results, the repeated use of ragweed resulted in toxic effects in rats and these results question the safety of long-term human consumption of common ragweed.
The medicinal use of the herb has started recently in Europe, even though common ragweed had never been part of folk medicine, and to the best of researchers' knowledge, the long-term consumption of the plant has never been examined. In an animal experiment, the repeated use of ragweed was nephrotoxic and had a controversial effect on brain tissue.
Cross-Reactivities and Drug Interactions
Approximately 20% of ragweed-allergic patients are sensitized to profilin and the calcium-binding allergens Amb a 9 and Amb a 10. Amb a 8 (profilin) showed extensive cross-reactivity with profilins from birch (Bet v 2), timothy grass (Phl p 12), and mugwort pollen (Art v 4). These cross-reactivities are clinically relevant when considering diagnosis and the choice of allergen immunotherapy.
For the prescription SLIT-tablet, a physician may decide that RAGWITEK is not the best treatment for patients who have asthma, who plan to become pregnant or are breast-feeding, who are unable or unwilling to administer epinephrine, or who are taking certain medicines, including other allergen immunotherapy.
Because ragweed belongs to the Asteraceae family, individuals with known hypersensitivity to other Asteraceae plants (such as chamomile, echinacea, or chrysanthemum) may be at elevated risk of cross-reactive sensitization. The sesquiterpene lactone content, which is responsible for both therapeutic-interest and contact-sensitizing properties, varies significantly by geographic origin and growth stage of the plant, introducing additional uncertainty for herbal preparations sourced from raw plant material.
References
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