Poison Lettuce: Properties, Dosage and Safety
Poison lettuce, also known as wild lettuce: what has been shown in animals, why there are no studies in humans, what symptoms of poisoning have been described, and who should avoid it.
Poison lettuce (Lactuca virosa), also sold as wild lettuce, is a plant from the aster family. Its milky sap contains bitter sesquiterpene lactones: lactucin and lactucopicrin. The analgesic and sedative effects of these compounds have been demonstrated in mice, but never in a controlled study in humans. The same plant circulates in trade under two names, and in supplement descriptions, it is accompanied by the word opium, which has no basis in its chemical composition. Below, I separate what has been measured from what has been repeated since the 19th century: what data comes from animal studies, why it is impossible to honestly provide a dosage, what symptoms of poisoning have been described in humans, and what the European food safety list says about this plant.
KEY INFORMATION
• The Polish botanical name of the species Lactuca virosa is poison lettuce; in Poland, the plant is an ephemeral, meaning a species sporadically introduced since the 19th century (Atlas of Polish Plants).
• The effects are due to sesquiterpene lactones, primarily lactucin and lactucopicrin; the plant does not contain opium alkaloids (EFSA plant list, 2012).
• In mice, doses of 15 and 30 mg/kg produced an analgesic effect comparable to ibuprofen at a dose of 30 mg/kg (Wesołowska et al., 2006).
• In the ClinicalTrials.gov registry, there is not a single registered clinical study of this plant (checked August 23, 2026).
• A series of eight poisonings in individuals aged 12 to 38 years has been described; one of them spent 48 hours in the intensive care unit (Besharat et al., 2009).
• Past reports of hyoscyamine-like alkaloids have not been confirmed by modern chemical analyses (EFSA plant list, 2012).
What is poison lettuce and is wild lettuce the same plant?
In the supplement trade, both names usually refer to the same species: Lactuca virosa. The Polish botanical name is poison lettuce, while wild lettuce is a commercial name, convenient because it is less frightening. However, confusion can be real, as another relative grows in Polish thickets.
This relative is compass lettuce (Lactuca serriola), a common archeophyte along roadsides and fallow lands. Poison lettuce itself originates from the western part of the Mediterranean basin and was introduced to Poland in the 19th century as a sporadically introduced plant that has not established itself (Atlas of Polish Plants). So if someone claims to have collected wild lettuce in a Polish meadow, they were almost certainly holding compass lettuce, not the species on the supplement label.
A common feature of both is the white milky sap that flows from any cut part of the plant. It carries the bitter sesquiterpene lactones and irritates mucous membranes, conjunctiva, and skin. English literature refers to wild lettuce for both species at once, which is why some online reports attribute data collected on another species to poison lettuce.
What does the milky sap contain and where did the name opium lettuce come from?
The dried milky sap was called lactucarium, and this is where the term opium lettuce comes from. The name describes the method of obtaining the raw material, which is cutting the stem and collecting the coagulating milk, not its composition. The sap contains sesquiterpene lactones, and it does not contain morphine or codeine.
The history of this name is well documented in Polish. 19th-century Polish medical literature described lactucarium as a sedative and analgesic with effects weaker than opium but free from its side effects, and pharmacists tried to obtain it from plants grown in the country. The attempts made at that time to identify the substance responsible for this effect ended in failure, and medical practice had to rely on the dried sap itself (Trojanowska, 2005).
Modern chemistry has closed the matter differently than advertising would like to close it. In the European EFSA plant list (2012), poison lettuce is listed with a note that the substances of interest are sesquiterpene lactones, and past information about the presence of hyoscyamine-like alkaloids has not been confirmed by modern analytical studies. The same entry notes that the milky sap is described as toxic.
What have studies shown, and what has not been checked in humans?
The studies concern isolated compounds and laboratory animals. Wesołowska et al. (2006) administered lactucin, lactucopicrin, and 11beta,13-dihydrolactucin to mice at doses of 15 and 30 mg/kg. In the hot plate test, the effect was similar to ibuprofen at a dose of 30 mg/kg, and in the tail reflex test, the dose of 30 mg/kg was comparable to ibuprofen at a dose of 60 mg/kg.
Lactucopicrin was the most potent. Sedation, measured by a decrease in spontaneous locomotor activity, occurred after lactucin and lactucopicrin, but not after dihydrolactucin. This result is based on isolated molecules, not on an extract from the plant.
The second source of animal data is even further from a product on the shelf. Ilgün et al. (2020) studied the milky saps of five species of the genus Lactuca growing in Turkey, and at a dose of 100 mg/kg, three of them produced sedation in mice, while two did not produce it at all. Poison lettuce was not included in this set.
There is nothing to summarize in humans. In the ClinicalTrials.gov registry, not a single clinical study of this plant is listed, and in the Europe PMC database, no work on it is marked as a clinical study or randomized controlled trial (checked August 23, 2026). This sentence carries more information than any number that could be inserted in its place.
How is poison lettuce dosed and is there a safe dose?
There is no established dosage, and no label will honestly provide it. No studies have been published in humans that would determine an effective or safe dose, so the numbers printed on the packaging of extracts are the manufacturer’s decision, not a measurement result.
Animal data cannot be converted into a capsule serving for three reasons at once. Pure compounds were administered, not an extract. Doses were calculated per kilogram of body weight of mice. The content of lactones in the raw material is variable: in HPLC measurement, it differed among species of the genus Lactuca to such an extent that some saps produced sedation while others did not (Ilgün et al., 2020).
The practical conclusion is short. If you are looking for a plant raw material with described dosing and data from human trials, poison lettuce is not a good choice, and better described are even preparations from passionflower, chamomile, or hops cones. If you still reach for the extract, treat the serving indicated on the packaging as the upper limit of an experiment worth discussing with a doctor. Products from this group can be found in the category of plant extracts.
When does poison lettuce harm and who should avoid it?
The milky sap irritates the skin and mucous membranes, and eating the fresh plant has been described as a cause of poisoning. Besharat et al. (2009) presented eight individuals aged 12 to 38 years who were admitted to the hospital after consuming this plant as a raw vegetable.
The clinical picture resembled an anticholinergic syndrome: reduced consciousness, agitation, dry mucous membranes, dilated pupils, urinary retention, weakened peristalsis, and in some patients also ataxia, visual disturbances, hallucinations, nausea, and vomiting. Treatment was supportive. All recovered and were discharged after 48 hours, with one person spending those two days in the intensive care unit due to prolonged loss of consciousness. No long-term complications were reported.
This must be contrasted with the fact that the same plant is listed in the EFSA plant list (2012) as a species whose entire above-ground part carries substances of concern. The table below summarizes situations where the risk is real.
| Situation | What is known about it | What to do about it |
|---|---|---|
| Pregnancy and breastfeeding | No safety data in humans | Do not use |
| Eating fresh plant | Eight described poisonings after consuming raw herb (Besharat 2009) | Do not eat raw, do not collect on your own |
| Contact of sap with skin and eyes | Milky sap irritates skin and mucous membranes, including conjunctiva (Atlas of Plants) | Gloves, immediate rinsing with water |
| Sedative medications and alcohol | No interaction studies in humans, in mice compounds reduced locomotor activity | Do not combine without consulting a doctor |
| Driving vehicles | Sedation effect has only been described in animals, it has not been measured in humans at all | Do not assume that the reaction will be mild |
| Children | The youngest patient in the described series of poisonings was 12 years old (Besharat 2009) | Do not administer |
Separately stands the issue of the commercial form. Poison lettuce is now sold not only as dried herb and extract but also as resin for vaporization and liquid for electronic cigarettes (Peace et al., 2020). Inhaling hot aerosol is a completely different route of administration than that described in the 19th century.
Frequently Asked Questions
Is poison lettuce the same as wild lettuce?
In commercial practice, yes. Both names usually refer to the species Lactuca virosa, with poison lettuce being the botanical name and wild lettuce being the marketing name. However, in a botanical context, the term wild lettuce is sometimes used for compass lettuce, or Lactuca serriola.
Does poison lettuce contain opium?
No. The term opium lettuce refers to the dried latex, called lactucarium, and the method of obtaining it by cutting the stem. The latex contains sesquiterpene lactones, mainly lactucin and lactucopicrin, not morphine or codeine.
How much poison lettuce can be safely taken?
It is unknown. No studies have been published in humans that would determine an effective or safe dose, and the doses given to mice referred to pure compounds calculated per kilogram of body weight. The number on the extract packaging is the manufacturer’s decision, not a measurement result.
Does poison lettuce help with sleep?
There is no evidence in humans. Sedation was measured in mice after administering lactucin and lactucopicrin, as well as after the latex of several other species of the genus Lactuca. None of these studies indicate whether and how the plant affects human sleep.
Can poison lettuce be smoked or vaporized?
Such products exist: wild lettuce is sold as powder, resin, and liquid for electronic cigarettes, and their composition is sometimes subject to chemical analyses. However, neither the effectiveness nor the safety of inhaling this raw material has been studied in humans.
Does poison lettuce grow in Poland?
Practically not. The species originates from the western part of the Mediterranean basin and in Poland is an ephemeral, meaning a plant sporadically introduced since the 19th century that has not established itself. Compass lettuce is common here instead.
Does poison lettuce interact with medications?
There are no interaction studies in humans, so the answer is: it is unknown. Since compounds from this plant reduced locomotor activity in animals, combining it with sedatives, sleeping pills, or alcohol requires a conversation with a doctor, not personal experimentation.
How does poison lettuce differ from compass lettuce?
These are two different species of the same genus. Compass lettuce, Lactuca serriola, is a common archeophyte along roadsides in Poland, and it is from this species that cultivated lettuce was selected. Poison lettuce, Lactuca virosa, appears only accidentally in the Polish flora.
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: 2026-08-24
