What is Costmary?

What is costmary?

Costmary is a tall, mint-scented herb from the daisy family. Its botanical name is Tanacetum balsamita. It is a close relative of tansy.

The long, grey-green leaves smell of balsam and spearmint. Cooks once used them to flavour ale, soups and cakes. German names for it are Frauenminze and Marienblatt.

Here is the honest verdict on evidence. There are no good human trials of costmary for any health problem. Long tradition is not proof that it works, and it is not proof that it is safe.

Treat costmary as a kitchen and garden herb. It is not a treatment for any illness.

How does Costmary work?

How is costmary thought to work?

No one has shown what costmary does in the human body. Everything below comes from lab work, not from people.

The leaf and its oil are rich in scented plant compounds. In test-tube studies, extracts slow the growth of some bacteria and fungi. Whether that happens on skin or in the gut is not known.

In laboratory tests the oil also shows antioxidant activity. That means it mops up reactive molecules in a dish. It tells you nothing about disease in a person.

The old digestive use is usually explained by bitterness and scent. Bitter, aromatic herbs can prompt saliva and gut movement. For costmary itself this has not been measured in people.

Some costmary plants are rich in thujone, a compound also found in wormwood. In animals, thujone can act on the brain and trigger seizures at high doses. That is a reason for caution, not a benefit.

What forms does Costmary come in?

How is costmary sold and used?

Costmary is a garden herb first and a product second. You will not find standardised capsules in most shops.

Common forms:

- Fresh leaves picked from a garden plant - Dried leaf, loose or inside herbal tea blends - A single dried leaf used as a scented bookmark, the old "Bible leaf" custom - Essential oil, sold for fragrance - Tincture (an alcohol extract), from specialist herb suppliers only

Never swallow the essential oil. Any oil is far more concentrated than a leaf, and thujone-rich oil is the real hazard here.

Fresh leaf in cooking is used in very small amounts. The flavour is strong and quickly becomes bitter.

Where it comes from:

What did tradition use costmary for?

Costmary spread through European monastery and cottage gardens from the Middle Ages onward. Monks and nuns grew it for scent, for flavouring ale and for salves.

The English name links the plant to the Virgin Mary. So do the German names Frauenminze and Marienblatt. Settlers later carried it to North America, where it became the "Bible leaf" pressed into psalm books.

Folk writers listed it for stomach upset, period pain, headache and wounds. Those were the claims of their day. They were never tested the way a medicine is tested now.

By the twentieth century the plant had largely dropped out of use. It survives mostly in heritage gardens and old recipe books.

What does Costmary help with?

• Mild indigestion and bloating: This is the most common folk use, taken as a weak leaf tea. Bitter, aromatic herbs can prompt saliva and gut movement. For costmary itself, that has never been tested in people. There is no trial showing it eases indigestion. If your symptoms keep coming back, that needs a doctor, not a herb.
• Stomach cramps: Old texts list costmary as a warming, cramp-easing herb. Lab work on related plants shows some muscle-relaxing activity in animal tissue. No human study has looked at costmary for cramps. Severe or sudden stomach pain is never a herb problem. Get it checked.
• Period pain: The "women's herb" names reflect long use for period problems. No trial has tested costmary for period pain. Related daisy-family herbs have mixed and limited evidence. Tradition here is strong and the evidence is absent. Pregnancy is a firm reason to avoid it.
• Headache: Folk use included sniffing the leaf or drinking the tea for headache. This may be a scent and ritual effect. Nothing has been measured in people. Its cousin feverfew has been studied for migraine. That evidence does not transfer to costmary.
• Minor wounds, stings and bruises: Crushed leaves and leaf salves were applied to small skin injuries. In test tubes, extracts slow the growth of some bacteria. Whether this works on real skin is not established. The plant can also cause rash in daisy-sensitive people. Clean water and a plaster are the safer first step.
• Flavouring and household scent: This use is real and needs no medical claim. Small amounts of leaf once flavoured ale, soups, salads and cakes. Dried leaves were laid in linen to scent it and deter moths. Culinary amounts are tiny. That is not the same as taking it for health.

Which foods are rich in Costmary?

Costmary is a flavouring herb, not a nutrient you get from foods. Tiny amounts of the fresh leaf were once used in ale, soups, salads and cakes. Cooking amounts are far smaller than any medicinal use.

What are the side effects of Costmary?

• Skin rash or itching after handling the fresh plant
• Allergic reaction in people sensitive to daisy-family plants
• Mouth or throat irritation from a strong tea
• Nausea, stomach pain or vomiting
• Headache or dizziness
• Seizures and liver harm, reported with thujone-rich oils rather than mild leaf tea

Good to know:

How common and how serious are these?

We do not know how common side effects are. No one has collected safety data on costmary in people.

Skin rash from handling the plant is the best-documented problem. It is usually mild and settles when you stop.

The serious risks sit with the essential oil and with thujone-rich plants. Swallowing oil can harm the brain and liver. That is why no oil dose appears on this page.

How much Costmary should you take?

• Recommended daily: How much do labels carry? There is no established dose for costmary. It is sold as a garden and flavouring herb, not as a measured supplement. Where dried leaf is packed for tea, labels often list about 1 to 2 g per cup. That is a label figure for the dried plant. It is not advice for you. Strength varies widely between plants. Thujone content is almost never printed on a pack. Ask a pharmacist or doctor before using costmary for any health reason. No dose can be given for the essential oil, because it should not be swallowed at all.
• Best time of day: Does timing matter? Not really. There is no evidence that any time of day works better. Traditionally the tea was taken after a heavy meal. That fits the digestive use, nothing more.
• With or without food: With or without food? The traditional pattern was after food, for digestion. Taking it with food may also lower the chance of stomach irritation. Strong or bitter teas are harsher on an empty stomach.
• Time to effect: How fast would anything happen? If a warm, mildly bitter tea settles your stomach, you would notice within about an hour. That may be the warm drink as much as the herb. No trial has measured any effect. It may do nothing at all. Treat that as the likely outcome.
• How long to take it: How long is it used for? Short-term only, if at all. Folk use was a few cups over a few days, not a daily habit. No study has looked at long-term use in people. Thujone can build up as a risk with repeated or strong doses. Do not take it daily for weeks or months. If a problem lasts more than a week or two, see a doctor.