The seeds look harmless enough. Small, angular, rust-brown, they come in plastic pouches at Middle Eastern grocers and in little brass bowls at wedding parties, where someone drops a pinch on hot charcoal and waves the smoke around the room. In Iran it is called esfand. In Turkey, üzerlik. Across North Africa and South Asia, harmal. In English the plant usually goes by Syrian rue, and lately it turns up in online shops too, sold as incense, a cleansing herb, or something vaguer.

If you have bought a bag, or a relative swears by a pinch of it in tea, this is what you should know before anyone swallows a single seed.

An old plant with a long résumé

Syrian rue is a scrubby desert perennial, rarely taller than a foot, native to the dry belt that runs from the Mediterranean and North Africa through Iran into Central Asia. It has narrow leaves, small white flowers with greenish veins, and round capsules that split in late summer to release the seeds.

People have used it for a very long time. Persian ritual tradition burned it to purify a space and ward off the evil eye, a custom that survives at weddings and New Year gatherings today. Medieval physicians, Avicenna among them, wrote about decoctions for abdominal pain. In parts of North Africa, powdered seed was scattered at doorways to keep misfortune out. Folk healers applied crushed-seed pastes to fungal skin infections, and the seeds also gave a reddish dye for wool and carpets. Burning them has a practical side as well: the smoke repels insects.

None of that history makes the seeds a gentle kitchen herb. The same chemistry that made harmal powerful enough to earn a place in so many traditions is the reason it lands people in emergency rooms.

What harmine and harmaline actually do

The seeds are rich in beta-carboline alkaloids, chiefly harmine, harmaline and tetrahydroharmine. Harmine and harmaline are reversible inhibitors of monoamine oxidase A, or MAO-A, the enzyme your body uses to break down serotonin, norepinephrine, dopamine and tyramine. Block it, and those chemicals pile up.

Doctors have prescribed MAO inhibitors for depression for decades, and they treat them with real caution. Patients on these drugs get a list of foods to avoid and a long list of medicines that must never be combined. A bag of harmal seeds comes with no such list, and the alkaloid content varies from batch to batch, so you cannot know how strong a given spoonful is.

Here is where the trouble usually starts:

• Antidepressants. SSRIs such as sertraline or fluoxetine, SNRIs, tricyclics and other MAOIs, combined with an MAO inhibitor, can trigger serotonin syndrome: agitation, sweating, fever, muscle rigidity and, in severe cases, seizures.
• Stimulants and decongestants. Amphetamines, ADHD medications, pseudoephedrine and similar sympathomimetic drugs can push blood pressure dangerously high.
• Tyramine-rich foods. Aged cheeses, cured or fermented meats, soy sauce, tap beers and some red wines can provoke a hypertensive crisis: pounding headache, chest pain, a racing pulse.
• Some blood pressure drugs and opioids. Certain pain medicines such as tramadol and meperidine are classic MAOI interaction risks, and the effect on blood pressure medication can be unpredictable.

Picture a 34-year-old who has taken sertraline for two years and feels steady on it. A friend hands her a jar of harmal tea "for digestion." Nothing about that exchange sounds alarming, which is exactly the problem.

The reference page on Peganum harmala uses and risks lists the same interaction categories plainly: SSRIs, other MAO inhibitors, sympathomimetics, certain antihypertensives and tyramine-rich foods. It also flags people with schizophrenia or bipolar disorder, since the psychoactive effects can tip someone toward mania.

Poisonings, pregnancy and the problem with self-dosing

Syrian rue poisoning is well documented in the medical literature, especially from Iran, Morocco and Turkey, where the seeds are easy to find. The pattern is fairly consistent. Within an hour or so, people develop nausea and repeated vomiting, then dizziness, tremor and unsteady walking. Many report visual hallucinations or confusion. Doctors often find a slow heart rate, sometimes low blood pressure, and in heavier exposures agitation or seizures. Most patients recover with supportive care, but serious cases need monitoring, and deaths have been reported.

Pregnancy deserves its own warning. Harmal has a long folk reputation as an abortifacient, and that reputation exists because the alkaloids can stimulate uterine contractions. Many reported poisonings involve women who took the seeds to end a pregnancy. If you are pregnant, trying to conceive or breastfeeding, do not take it in any form. The same caution applies to children, older adults and anyone with heart disease.

Why is self-dosing so risky when traditional healers used the plant for centuries? A few reasons stack up:

• Alkaloid content swings widely with growing region, harvest and storage, and retail seeds are almost never tested.
• The line between a dose that causes no effect and one that causes vomiting and tremor is narrow.
• Many people who reach for harmal are already on prescription medication, often antidepressants, and do not think of an "incense herb" as a drug.
• Online sellers rarely mention interactions, and some actively market the seeds for psychoactive use.

Burning seeds as incense is a different exposure from eating them, and the traditional practice is not the main source of poisonings. Still, ventilate the room, since smoke irritates airways, and keep the bag away from children.

If someone has already taken harmal, whether in tea, capsules or chewed seeds, and especially if they also take an antidepressant, a stimulant or a blood pressure medicine, do not wait to see what happens. In the US, call Poison Control at 1-800-222-1222. The free line runs around the clock, and specialists can tell you whether home observation is reasonable or whether the person needs an emergency department. Have the package, the amount taken and a list of the person's medications ready when you call. If there is chest pain, a severe headache, a very slow or very fast pulse, confusion, fainting or a seizure, call 911.

Then, when things have calmed down, mention it to the prescribing doctor. A pharmacist can also run a quick interaction check against everything on the person's list. People skip herbs in that conversation because they seem minor. With an MAO inhibitor involved, they are not.

Syrian rue carries real cultural weight, and nobody needs to stop burning a pinch at a family wedding. Swallowing it is another matter. Treat the seeds the way you would treat an unlabeled prescription drug, because chemically that is close to what they are.