Poison Lettuce and Wild Lettuce: Effects and Dosage

Poison lettuce (Lactuca virosa) is a wild relative of lettuce from the aster family. Its dried latex was once called lettuce opium. Does this plant really work? Evidence comes from studies on mice that received pure compounds, not the plant. Lactucin and lactucopicrin, bitter lactones typical for it and for chicory, in doses of 15 and 30 mg/kg acted in the hot plate test analgesically similar to ibuprofen at a dose of 30 mg/kg (Wesołowska et al., 2006). In humans, mainly poisonings have been described, and the ClinicalTrials.gov registry did not contain any studies on this plant as of September 16, 2026. We also did not find any work that would establish an effective or safe dose. This text will inform you about how poison lettuce differs from compass lettuce and what is unknown about its smoking.

KEY INFORMATION
• Isolated lactones typical for poison lettuce acted analgesically in mice at doses of 15 and 30 mg/kg (Wesołowska et al., 2006).
• There are no studies on this plant in ClinicalTrials.gov (as of September 16, 2026).
• Eight poisonings in individuals aged 12-38 were reported (Besharat et al., 2009).
• There is no work on the smoke from this plant in PubMed (as of September 16, 2026).

What is poison lettuce and is wild lettuce the same plant?

Poison lettuce, also called toxic lettuce, is a species of Lactuca virosa from the aster family. It originates from the Mediterranean region. It arrived in Poland in the 19th century but did not become established and is only occasionally brought here (Atlas of Polish Plants, based on a work from 2012). The name “wild lettuce” is not a certain synonym for it, as it is shared by two different species.

The second is compass lettuce (Lactuca serriola), in older works Lactuca scariola. In Poland, it is common along roadsides, fallow lands, and ruderal places (Atlas of Polish Plants). Both species are called wild lettuce in English (Chadha and Florentine, 2021; Besharat et al., 2009).

Where does this confusion come from? It has a long history. In the 1835 Pharmacy textbook, wild lettuce, or L. scariola, was described as a plant that herbalists mistakenly brought instead of poison lettuce (Trojanowska, 2005). Anyone today collecting wild lettuce in a Polish field is almost certainly holding compass lettuce.

The comparison of these sources leads to a simple conclusion: the name “wild lettuce” alone does not indicate which species is inside. The Latin name is what determines it. Both species have white latex, but the atlas describes poison lettuce as slightly toxic and irritating to the skin. We did not find such a note for compass lettuce.

Does poison lettuce contain opium and where did this name come from?

There is no evidence that it contains opium components. In the 19th century, morphine was suspected in the latex of lettuce, but analyses of dried latex did not show components characteristic of opium (Trojanowska, 2005). The active substance was not established at that time. The name opium lettuce came from the attributed effects, and comparisons with opium were revived by a report from 1792.

The dried latex of lettuce was called lactucarium, in Polish łoczyżnik. A physician from Philadelphia, Redman Coxe, compared the “opium” from lettuce with poppy opium (Medical and Physical Journal, 1801).

The first Polish pharmacopoeia from 1817 mentioned poison lettuce. Lactucarium was classified as a narcotic raw material, and contemporary authors wrote that it acted weaker than opium but without its side effects. This is an opinion from the era, not a result of controlled research. However, contemporary authors described poisonings after larger doses (Trojanowska, 2005). Preparations from poison lettuce or sown lettuce appeared in the pharmacopoeias of several countries until the early 20th century (Ujváry, 2014).

What do modern data say? They do not indicate an opioid mechanism. According to a review from 2014, the calming and analgesic effects of lactucin were confirmed in mice, but opioid receptors in vitro did not react to it. The symptoms of poisoning with wild lettuce in humans differ from those of opiates (Ujváry, 2014).

What compounds does the latex contain and is there hyoscyamine in it?

The best-described compounds are bitter sesquiterpene lactones: lactucin, lactucopicrin, and 11β,13-dihydrolactucin, typical for poison lettuce and chicory (Wesołowska et al., 2006). The EFSA plant compendium lists two of them for this species, lactucin and lactucopicrin (EFSA, data collection from 2018). Whether the latex contains hyoscyamine is currently unknown.

The presence in the compendium is not a safety assessment. EFSA states that the database does not determine whether the plant is safe, but helps indicate possible hazards (EFSA, Compendium of botanicals). In the same collection for poison lettuce, it was noted that its latex was described as toxic.

Regarding hyoscyamine, sources diverge. The description of a series of poisonings from 2009 states in the introduction that lettuce contains trace amounts of this alkaloid. It cites a textbook published in Tehran in 1978 (Besharat et al., 2009). In the EFSA collection and in Ujváry’s review, there is no mention of hyoscyamine for this species, but the lack of an entry does not prove the absence of the compound. We did not find any modern analysis that would resolve this. The absence of morphine in reviewed sources is based only on 19th-century analyses.

What did studies on mice show?

They showed analgesic and calming effects of pure lactones, but only in animals. In the hot plate test, lactucin, lactucopicrin, and 11β,13-dihydrolactucin at doses of 15 and 30 mg/kg acted similarly to ibuprofen at a dose of 30 mg/kg (Wesołowska et al., 2006). Individual compounds were studied, not the dried plant or extract.

In the tail flick test, a dose of 30 mg/kg equaled ibuprofen at a dose of 60 mg/kg. Lactucopicrin had the strongest analgesic effect. Calming, measured by a decrease in spontaneous motor activity, was provided by lactucin and lactucopicrin, but not by dihydrolactucin. The summary does not provide the route of administration or group sizes.

The second work examined latex itself, but from other species. A team from Turkey injected mice with latex from five Lactuca species at a dose of 100 mg/kg, with 6 animals in each group. Three species provided calming, including compass lettuce, while two did not provide any. Poison lettuce was not included in the set (Ilgün et al., 2020).

A more interesting result is the chemical finding. The highest amount of lactucin, 57.53 mg per gram, was found in the latex of compass lettuce, yet it calmed less than the latex of L. saligna. The authors conclude that calming cannot be explained by lactucin alone and suspect interaction with lactucopicrin or other components of the latex. Did any of these results apply to humans? No one has checked that.

Does poison lettuce affect sleep or pain in humans?

There is no evidence for this, as we did not find any human studies that would test it. The ClinicalTrials.gov registry returned 0 studies for the term “Lactuca virosa” as of September 16, 2026. The same was true for the terms “wild lettuce” and lactucarium. In the Europe PMC database, no work on this species was marked as a clinical study or as a randomized trial.

In PubMed, the term “Lactuca virosa” yields 21 works (PubMed, as of September 16, 2026). Three of them directly concern humans. These are the described poisoning series, a French description of misuse without a summary in PubMed, and a note from 1815 about its use in whooping cough. None of these is a clinical study.

There is even a lack of absorption data. The only measurements of these lactones in human blood that we found concern chicory. In a study, 16 healthy volunteers drank 150 g of chicory juice, and 7.03% of the ingested amount of lactones was recovered in the blood (Weng et al., 2020). This is a different plant and one oral dose. Therefore, the dose from studies on mice does not indicate how much of the compound would reach human blood.

How to dose poison lettuce and is there a safe dose?

No established dosing exists. We did not find any human studies that would establish an effective or safe dose. The European Medicines Agency has no document for this plant. In its list of herbal substances obtained on September 16, 2026, there is no Lactuca species (EMA, list of herbal substances). Therefore, there is no official dosing.

The numbers from studies on mice cannot be converted to a human portion. Animals received pure compounds or latex, not a ready extract. Doses were calculated per kilogram of body weight, and latex was injected into the peritoneal cavity. The profile of lactones also varied between varieties and species of lettuce, and the proportion of their compounds in latex changed with the plant’s developmental phase (Sessa et al., 2000).

Historical sources provide only a warning here. 19th-century textbooks stated that larger doses of lactucarium led to poisoning with intoxication and dizziness, and even to coma (Trojanowska, 2005). In the Iranian series of poisonings, the severity of symptoms depended on the amount consumed, but this is known only from patient reports (Besharat et al., 2009). The lack of an established dose does not mean that a small portion is safe. It only means that we did not find any work that would test that.

In contrast, three other herbs have established monographs with dosing from EMA, but the indications were based solely on long-term use, not on clinical studies. For passionflower and hops, the indication includes help with falling asleep, while for chamomile, there is no such indication. We write about them in texts about passionflower for sleep and anxiety and about chamomile for sleep, and separately about hops cones.

What does the extract from poison lettuce contain?

This is unknown, as we did not find any published analysis of extracts sold in Poland. The only modern analysis of products with wild lettuce that we found comes from the USA. Researchers bought liquids, extracts, and powders from 8 “herbs” from one online seller. In the powder from wild lettuce, they detected coumarin, but did not find lactucins in any product (Peace et al., 2020).

For wild lettuce, a liquid for e-cigarettes and powder were examined. No expected compounds were detected in the liquid. The authors caution that the extraction with methanol and the sensitivity of the spectrometer may have lowered detectability. The work does not describe confirmation of the raw material species. Therefore, the absence of lactucin in the result does not prove that it was not there.

Preparations from wild lettuce are widely offered online and in herbal shops (Ujváry, 2014). If an extract, also in the category of plant extracts, is described only as “wild lettuce,” it is unknown which species is inside. We did not find studies that would establish its dose.

Ready liquids carry another risk. A review of vaporizing substances lists liquids with plant extracts, including wild lettuce, and warns that they may be mixed with synthetic cannabinoids (Varlet, 2016). In laboratory and animal studies, such cannabinoids acted 2 to 100 times stronger than THC, and in humans, tachycardia and psychoses were reported among other effects (Castaneto et al., 2014).

What symptoms does poisoning with poison lettuce cause?

The most commonly described symptoms were dilated pupils, dizziness, anxiety, and urinary retention, which the authors associated with an anticholinergic mechanism. In the Iranian case series, 8 individuals aged 12 to 38 were hospitalized after eating a plant identified as wild lettuce. All recovered and were discharged from the hospital after 48 hours (Besharat et al., 2009).

Treatment was supportive: intravenous fluids and gastric lavage, followed by activated charcoal with sorbitol. One person (patient 1) spent 48 hours in intensive care due to prolonged loss of consciousness. No lasting complications were reported. However, this is a case series. The laboratory confirmed small fragments of wild lettuce in gastric washings, but the work does not describe the identification of the species, and the amount consumed was not measured.

The second description concerns a different route. Three young adults injected an extract of wild lettuce intravenously, and one also injected an extract of valerian root. All quickly became ill: they had fever with chills and abdominal and back pain. They recovered within 3 days, and the authors did not find any effects similar to opiates (Mullins and Horowitz, 1998). The summary does not specify the species of lettuce.

The authors of the Iranian series advise against eating unknown plants, including herbs, and to seek medical help immediately if poisoning is suspected. In case of loss of consciousness, call 112.

Who should avoid poison lettuce?

Primarily groups for whom we found no studies: pregnant and breastfeeding individuals, children, and those taking sedative medications. Caution also applies to those allergic to aster family plants. In two Danish studies, 11% and 22% of patients allergic to this family had a positive reaction in patch tests to sown lettuce (Paulsen and Andersen, 2016).

General rules for combining herbs with medications are summarized in the table which herbs should not be combined.

Can you smoke poison lettuce or add it to a joint?

It is unknown what is produced in the smoke of poison lettuce: there are no such measurements in the reviewed sources. Of the 21 works on this species in PubMed (as of September 16, 2026), none concern smoke, aerosol, or burning. We also did not find any studies that would check whether lactones survive the burning of the leaf.

When substituting tobacco with herb in a joint, nicotine disappears, but not the smoke. Carbon monoxide is produced when any plant is burned, and there is no evidence that smoke from herbs is less harmful than tobacco smoke. We gathered this data in the text about what to smoke instead of tobacco. Poison lettuce has no advantage here: nothing is known about its smoke, and it can cause poisoning when eaten.

Substituting the additive does not change the law either. Cannabis material with a delta-9-THC and THCA sum above 0.3% is a narcotic in Poland (art. 4 point 37 of the Act on Counteracting Drug Addiction, Journal of Laws 2023, item 1939, as amended).

In the sources we reviewed, inhaling poison lettuce has no supporting studies. In the 19th-century practice described by Trojanowska, lactucarium was administered in pills and syrups, and externally for eye inflammations. This work does not describe smoking as a route of administration. Today, liquids for e-cigarettes and powders are in circulation, but in the analysis by Peace et al., only the products were checked, not the aerosol.

Does a vaporizer change anything here? In a study on cannabis, heating the dried material without burning produced less carbon monoxide in exhaled air than smoking (Abrams et al., 2007). We provide temperature ranges for several other herbs in the guide to herb vaporization. These are values from device instructions, not from measurements.

For poison lettuce, we found neither a comparison with smoking nor a measurement from which a temperature could be provided. Therefore, the result from cannabis cannot be transferred to its aerosol. The lack of data does not mean it is safe.

Is poison lettuce legal in Poland?

Poison lettuce does not appear in the Polish list of controlled substances. It is not in the consolidated text or in the amendments from 2025 and 2026 (regulation of the Minister of Health, consolidated text Journal of Laws 2024, item 1139, as amended). The list includes 15 plants along with dried and extracted forms, such as sage (Salvia divinorum) and kratom (Mitragyna speciosa), and separately cannabis other than fiber.

The absence from the list is not a safety assessment. A review of analytical methods from 2020 discusses poison lettuce among new psychoactive substances of natural origin, alongside sage and kratom (Lo Faro et al., 2020). This is a classification by the authors of the review, not a legal status. EFSA also cautions that its plant compendium has no legal force.

The law also restricts how to talk about such products. The Act on Counteracting Drug Addiction prohibits advertising and promoting products by suggesting that they act like narcotic or psychotropic substances (art. 20 sec. 3, consolidated text Journal of Laws 2023, item 1939, as amended). A description promising effects similar to opium is therefore a warning signal.

Frequently Asked Questions

Is poison lettuce the same as wild lettuce?

Not always. In English, wild lettuce refers to both poison lettuce (Lactuca virosa, Besharat et al., 2009) and compass lettuce (Lactuca serriola, Chadha and Florentine, 2021). In Polish works from the 19th century, “wild lettuce” referred to compass lettuce, which is now common along roadsides. The species is determined only by the Latin name.

Does poison lettuce contain opium?

There is no evidence for that. 19th-century analyses of dried latex did not show components characteristic of opium (Trojanowska, 2005). According to Ujváry’s review from 2014, opioid receptors in vitro did not react to lactucin, and the symptoms of poisoning with wild lettuce differ from those of opiates. The name opium lettuce comes from historical comparisons of effects.

What is a safe dose of poison lettuce?

We did not find any human studies that would establish an effective or safe dose. The European Medicines Agency has no document for this plant (list from September 16, 2026). Doses of 15 and 30 mg/kg from studies on mice concerned pure compounds and do not translate to humans.

Does poison lettuce help with sleep or pain?

This has not been demonstrated in humans. The calming and analgesic effects of lactucin and lactucopicrin were measured in mice (Wesołowska et al., 2006). The ClinicalTrials.gov registry did not contain any studies on this plant as of September 16, 2026, and no work on it is marked as a clinical study in the Europe PMC database.

Can you get poisoned by poison lettuce?

Yes. In an Iranian case series, 8 people aged 12-38 were hospitalized after eating fresh wild lettuce. One had reduced consciousness, another lost consciousness, and two experienced hallucinations. All were discharged from the hospital after 48 hours, and the person with reduced consciousness spent that time in intensive care (Besharat et al., 2009). No lasting complications were reported.

Can you smoke or vaporize poison lettuce?

We did not find any measurements of what is produced in its smoke or aerosol, and the lack of measurement does not imply safety. Of the 21 works on this species in PubMed (as of September 16, 2026), none concerned smoking or vaporization. Carbon monoxide is produced when any plant is burned. We also did not find vaporization temperatures based on measurements for poison lettuce.

This article is for informational and educational purposes and does not replace consultation with a doctor. If you are pregnant, breastfeeding, taking medications, or have chronic conditions, consult the use of supplements or herbs with a specialist.

Author: Michał Waluk · Published: 2026-08-24 · Updated: 2026-09-17