Prickly Lettuce (Lactuca serriola): Benefits, Traditional Uses & Safety

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Prickly lettuce (Lactuca serriola) is a tall, bitter-tasting wild relative of garden lettuce that has been used in European folk medicine for centuries as a mild sedative, cough remedy and pain reliever. Most of what you will read about its benefits, however, comes from tradition and early animal research — not from modern human trials — and anyone considering it should understand both the history and the limits of the evidence.

This guide explains what prickly lettuce is, what its milky sap (lactucarium) actually contains, what researchers have and have not shown, and when it should be avoided.

What is prickly lettuce?

Lactuca serriola is an annual or biennial plant in the daisy family (Asteraceae), growing 40 cm to over 1.5 m tall with a stiff stem, toothed leaves with prickly spines along the midrib, and small pale-yellow flowers that later form fluffy wind-dispersed seeds[Hanif et al., 2021]. It is native to Europe, western Asia and north Africa, and has now naturalized on every continent except Antarctica, usually on roadsides, field edges and disturbed ground.

It is sometimes called the “compass plant” because its upper leaves twist to stand vertically with their edges pointing roughly north–south — an adaptation that helps it survive hot, dry climates. Botanically, L. serriola is the wild ancestor of cultivated lettuce (Lactuca sativa), which is why their leaves look so similar when young[Hanif et al., 2021].

How it differs from garden lettuce and wild lettuce (L. virosa)

Three species are routinely confused:

• Garden lettuce (L. sativa) — tender, mild, selectively bred for salads. Contains only trace amounts of the bitter compounds described below.
• Prickly lettuce (L. serriola) — the wild progenitor of garden lettuce, bitter and spiny. Contains meaningful amounts of lactucarium, especially at flowering.
• Wild lettuce / opium lettuce (L. virosa) — a separate European species historically considered the richest source of lactucarium and the official source in old pharmacopoeias [Chemeurope, n.d.].

Most 19th-century medical texts referred specifically to L. virosa when describing “lettuce opium,” although some authors noted that L. serriola could also yield usable lactucarium[Chemeurope, n.d.]. A lot of modern herbal writing blurs this distinction and treats the two as interchangeable, which they are not.

What’s actually in prickly lettuce? The lactucarium story

When any part of a prickly lettuce plant is cut, a milky white latex flows from the wound. Left to dry, this latex hardens into a brown, resinous substance called lactucarium, historically nicknamed “lettuce opium” because of its faintly sedative effects — not because it contains any actual opium alkaloids.

Lactucarium’s most studied constituents are a group of bitter sesquiterpene lactones, mainly:

• Lactucin
• Lactucopicrin
• 11β,13-dihydrolactucin

These compounds are also found in chicory (Cichorium intybus) and in small amounts in cultivated lettuce[Wesolowska et al., 2006]. Concentrations rise sharply as the plant matures and peak around flowering, which is why traditional harvesters always used fully grown, bolting plants.

Lactucarium was listed in the United States Pharmacopeia from 1820 into the early 20th century and in the 1911 British Pharmaceutical Codex, where it was standardized for use in cough syrups and mild sleep-inducing lozenges[Chemeurope, n.d.]. It was dropped from both as synthetic sedatives and cough suppressants took over.

Traditional uses of prickly lettuce

Across European, Middle Eastern and South Asian folk traditions, prickly lettuce (and its close relative L. virosa) has been used for:

• Restlessness and occasional difficulty sleeping
• Dry, irritating cough and whooping cough
• Mild pain, including menstrual and muscle pain
• Nervous tension and anxiety
• Reducing excitability

Some older texts also described anaphrodisiac (“passion-cooling”) effects going back to the Pythagoreans, and the plant appears in classical references by Dioscorides[Wikipedia, 2025]. These historical claims are not supported by modern evidence and should be read as cultural context, not medical advice.

What the evidence actually shows

Honest summary first: modern controlled human trials on prickly lettuce are essentially absent. Almost all of the pharmacological data we have comes from (a) isolated compounds tested in rodents, (b) crude plant extracts tested on isolated animal tissue, and (c) historical case reports. That is enough to say “there is likely something there,” but not enough to say it treats any specific condition.

Sedation and sleep

In a frequently cited 2006 study, Polish researchers gave mice isolated lactucin, lactucopicrin and 11β,13-dihydrolactucin and measured locomotor activity. Lactucin and lactucopicrin — but not the dihydro form — significantly reduced spontaneous movement, consistent with a mild sedative effect[Wesolowska et al., 2006]. No comparable placebo-controlled sleep trial has been published in humans, so any claim that prickly lettuce “works for insomnia” rests on folklore plus animal data. Readers looking for diet-based calm may be better served by eating foods that support healthy nerves and brain function.

Pain relief

The same 2006 study tested the three sesquiterpene lactones in the hot-plate and tail-flick tests, standard rodent models of acute pain. At 15–30 mg/kg, the compounds produced analgesic effects comparable to ibuprofen at 30 mg/kg, with lactucopicrin appearing most potent[Wesolowska et al., 2006]. These are promising preclinical results — they tell us the molecules are bioactive, not that a cup of prickly lettuce tea relieves pain in humans.

Cough, asthma and respiratory use

A 2013 pharmacology paper tested a methanol extract of Lactuca serriola on isolated rabbit trachea and found it relaxed airway smooth muscle in a concentration-dependent way — a plausible mechanism for a cough suppressant and bronchodilator[Janbaz et al., 2013]. This is again in-vitro rabbit-tissue data, not clinical evidence. For a traditional respiratory remedy with stronger food-based support, see onions for respiratory support.

Digestive and vascular effects

In the same study, the extract produced a dose-dependent effect on rabbit intestinal tissue — contractile at lower concentrations and relaxant at higher ones — and relaxed aortic rings[Janbaz et al., 2013]. The authors suggested calcium-channel-blocking activity as the likely mechanism. Once again: interesting preclinical signal, no human validation.

The table below summarizes where the evidence stands today.

Claim	Evidence level	What kind of data
Mild sedative / sleep aid	Limited	Animal models + historical pharmacopoeia
Analgesic (pain relief)	Limited	Isolated compounds in mice
Cough / bronchodilator	Very limited	Isolated rabbit airway tissue
Antispasmodic	Very limited	Isolated rabbit gut/aorta
Cures insomnia, pain or whooping cough	Not supported	No controlled human trials

How prickly lettuce has traditionally been prepared

Traditional herbalists describe three main preparations. These are reported for historical context only — see the safety section below before considering them.

• Decoction of leaves. Roughly 100 g of fresh flowering plant simmered for 10 minutes in 1 litre of water, strained and sweetened with honey.
• Dried lactucarium. The air-dried latex, historically dosed at 0.1–1 g per day in lozenges or pills. This is the preparation used in the 19th-century pharmacopoeias [Chemeurope, n.d.].
• Fresh juice or tincture. Made from flowering aerial parts, often combined with related sleep herbs like valerian, hops or passionflower [MEpedia, n.d.].

Concentrations of the active sesquiterpene lactones are very low in young plants and highest once the plant bolts into flower, which is why rosettes eaten as salad have little medicinal effect[PFAF, n.d.]. Large servings of the leaves as food can cause digestive upset. Bitter astringent plants such as five finger grass are sometimes combined in traditional European remedies.

Safety, side effects and drug interactions

Prickly lettuce is not a harmless herb. Because the active compounds act on the central nervous system and because the plant can be concentrated into potent extracts, both the U.S. RxList monograph and a documented case series describe real adverse events.

Who should avoid prickly lettuce

Based on the RxList / Natural Medicines safety monograph for wild lettuce[RxList, 2021], the following groups should avoid it:

• Pregnant or breastfeeding women — insufficient safety data.
• People with narrow-angle glaucoma — constituents may worsen the condition.
• People with benign prostatic hyperplasia (BPH) or other urinary retention — may make urination harder.
• People allergic to ragweed, daisies, chrysanthemums or marigolds — all members of the same Asteraceae family, and cross-reactivity is common.
• Anyone taking CNS depressants — including benzodiazepines, opioids, alcohol, prescription sleep medication, or other sedating herbs. Combined effects can be excessive.
• Anyone scheduled for surgery — stop at least two weeks before any procedure because of possible interaction with anesthesia.
• Children — despite older texts that claimed it was safe for “excitable children,” there is no modern safety data in pediatric use and the sedating compounds are not dose-standardized.

Reported side effects

Small culinary amounts of young leaves are generally well tolerated. Larger doses of concentrated extracts or the dried latex can cause[RxList, 2021]:

• Sweating and fast heartbeat
• Pupil dilation, blurred vision and ringing in the ears
• Dizziness and excessive sedation
• Nausea, stomach upset
• In severe cases, slowed or difficult breathing

A 2009 case report in BMJ Case Reports described six young men in Iran who developed fever, chills, abdominal and back pain, headache and elevated white blood cell counts after eating wild lettuce; all recovered with supportive care, but the authors noted that the plant can cause meaningful toxicity when consumed in quantity[Besharat et al., 2009]. Injecting home-made wild lettuce extract has also caused serious illness and should never be attempted[Mullins & Horowitz, 1998].

When to talk to a healthcare professional

See a clinician rather than self-treating if you have:

• Insomnia that lasts more than a few weeks
• A cough that persists more than three weeks, produces blood, or comes with shortness of breath, chest pain, fever or unintentional weight loss
• Severe or worsening pain, or pain accompanied by numbness, weakness or bladder/bowel changes
• Signs of an allergic reaction — hives, swelling, wheezing or difficulty breathing after any exposure to the plant

Realistic expectations

Prickly lettuce is a genuinely interesting historical medicine with plausible, preclinical support for mild sedative, analgesic and antitussive activity. It is not a substitute for evaluated treatments. If something matters enough to treat, it matters enough to diagnose first.

A reasonable way to think about it: prickly lettuce belongs in the same category as many traditional bitter herbs — worth knowing about, sometimes useful as part of a broader approach to relaxation or a tickly cough, but not a stand-alone cure, and not appropriate in the concentrated doses some online sources promote.

For calming herbs with much stronger modern evidence, see our guides to ashwagandha and lavender.

⚠ Health Disclaimer The information in this article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Prickly lettuce and lactucarium are not approved by the FDA or EMA to treat any disease. Do not use prickly lettuce, wild lettuce or any lactucarium-containing product if you are pregnant, breastfeeding, have narrow-angle glaucoma or benign prostatic hyperplasia, are allergic to plants in the Asteraceae/ragweed family, are taking sedative or CNS-depressant medications, or are scheduled for surgery. Always speak with a qualified healthcare professional before starting any herbal remedy, especially if you have a medical condition, take prescription medication, or are considering giving herbs to a child.

Frequently Asked Questions

References

• Wesolowska A, Nikiforuk A, Michalska K, Kisiel W, Chojnacka-Wojcik E. (2006). Analgesic and sedative activities of lactucin and some lactucin-like guaianolides in mice. J Ethnopharmacol. 107(2):254-8.→ View source
• Janbaz KH, Latif MF, Saqib F, Imran I, Zia-Ul-Haq M, De Feo V. (2013). Pharmacological effects of Lactuca serriola L. in experimental model of gastrointestinal, respiratory, and vascular ailments. Evid Based Complement Alternat Med. 2013:304394.→ View source
• Hanif Z, Naeem M, Ali HH, Tanveer A, et al. (2021). Biology, ecology, distribution and control of the invasive weed, Lactuca serriola L. (wild lettuce): a global review. Plants. 10(10):2088.→ View source
• Besharat S, Besharat M, Jabbari A. (2009). Wild lettuce (Lactuca virosa) toxicity. BMJ Case Rep. 2009:bcr06.2008.0134.→ View source
• RxList / Natural Medicines Comprehensive Database. Wild Lettuce: Uses, Side Effects & Warnings.→ View source
• Chemeurope Encyclopedia. Lactucarium.→ View source
• Plants For A Future. Lactuca serriola — Prickly Lettuce.→ View source
• Mullins ME, Horowitz BZ. (1998). The case of the salad shooters: intravenous injection of wild lettuce extract. Vet Hum Toxicol. 40(5):290-1.→ View source
• Wikipedia contributors. Lactuca serriola. → View source