Bog myrtle

What is Bog myrtle?

Bog myrtle is a small, woody shrub that grows in bogs and wet moorland across northern Europe. The leaves smell strongly of resin and spice when you crush them. People once used them to flavour ale and to keep biting insects away.

Today it is sold as dried leaf, as an essential oil, and inside some skin and repellent products. A few brewers still use the leaf in traditional gruit ales. Nordic makers also use it in flavoured spirits.

The honest verdict: human evidence is thin. Small outdoor tests suggest the oil gives short, partial protection from biting midges. Nothing in people supports the old internal uses, and long folk use is not proof that a plant works or that it is safe.

How does Bog myrtle work?

The best-supported idea is simple: the strong-smelling oil in the leaf puts biting insects off landing.

The oil is rich in terpenes, a family of plant scent chemicals. In laboratory and small field tests, these deter midges and some mosquitoes. The effect fades as the scent fades, so it is short.

In test-tube studies, bog myrtle extracts slow the growth of some bacteria and fungi. Cell studies also report lower levels of inflammation markers. Whether any of this happens in a person who drinks a tea or rubs on the oil has not been shown.

One mechanism matters for safety rather than benefit. The oil contains germacrone, a compound linked in animal studies to harm in pregnancy. That animal work is the main reason the plant is kept away from pregnant women.

What forms does Bog myrtle come in?

Dried leaf and leafy twigs, loose or in tea bags.

Essential oil, steam-distilled from the leaf. It is sold for use on skin after dilution, or in sprays.

Skin products: insect repellent sprays and lotions, soaps, and some cosmetic creams.

Tinctures, which are alcohol extracts of the leaf. These are less common.

Flavouring uses: gruit-style ales, aquavit and other flavoured spirits, and a few traditional Nordic dishes.

Dried sprigs for cupboards and bedding, used to put off moths and fleas.

Strength is not standardised. Two products with the same name can differ widely in how much oil they contain.

Where it comes from:

Bog myrtle has a long, well recorded place in northern European folk life. It is called Gagelstrauch in German and pors in Danish.

Before hops took over, brewers across Scandinavia, Germany, the Low Countries and Britain used it in gruit ale. It added bitterness and scent. Writers of the time also claimed it made the drink more heady.

Households hung sprigs in beds and cupboards against fleas and moths. Walkers and farm workers rubbed leaves on skin against midges, especially in Scotland and Ireland.

Folk healers used leaf teas for stomach upsets, worms, itching skin and as a spring tonic. It was also used to bring on a late period, which in practice sometimes meant trying to end a pregnancy. That use was dangerous then and is dangerous now.

This page records those uses. It does not suggest you copy them.

What does Bog myrtle help with?

• Keeping biting midges and mosquitoes off skin: This is the one use with any human data. Scottish field tests with volunteers found that bog myrtle oil cut the number of midge bites compared with no repellent. Protection was weaker and shorter than DEET. The studies were small and done outdoors, where conditions vary. Treat it as a mild, short-lived option rather than a reliable shield.
• Keeping moths and fleas out of bedding and cupboards: A very old household use across northern Europe, based on the strong scent. Laboratory work shows the oil puts off some insects. No study has tested dried sprigs in a real wardrobe or bed. The effect, if any, likely fades as the scent fades.
• Flavouring ale and spirits: This is a food and drink use, not a health claim. Gruit brewers used the leaf for bitterness and aroma before hops became standard. It still appears in some craft ales and in Nordic spirits. The same pregnancy warning applies to drinks flavoured with it.
• Traditional use for stomach upset and poor appetite: Folk healers gave bitter leaf teas for wind, poor appetite and sluggish digestion. There are no human trials. Bitter plants can stir appetite in general, but that has not been tested for bog myrtle. Strong teas can also irritate the stomach, so the risk may outweigh any gain.
• Traditional use for itchy skin and minor skin complaints: Washes and oils were applied to itchy or irritated skin. Test-tube work shows the extract slows some bacteria and fungi. Nobody has shown that this happens on human skin. The oil itself can cause an allergic rash in some people.
• Traditional use as a spring tonic: "Tonic" was a broad old idea, meaning a drink taken to perk you up after winter. It does not match any condition a doctor would recognise. There is no evidence that bog myrtle improves energy, mood or general health.

Which foods are rich in Bog myrtle?

Bog myrtle is a flavouring, not a nutrient, so no food is "rich in it".

You may meet it in gruit-style craft ales, in Nordic aquavit and snaps, and in a few traditional dishes. Amounts are usually small.

The pregnancy warning still applies to these drinks and dishes. If you are pregnant, read labels on specialist ales and spirits.

What are the side effects of Bog myrtle?

• Allergic skin rash or contact dermatitis from the oil
• Stinging or redness on broken or shaved skin
• Eye irritation if the oil or spray gets in the eyes
• Coughing or airway irritation from strong vapour
• Nausea, stomach ache or diarrhoea from strong teas
• Headache from the strong scent

Good to know:

Most reported problems are skin reactions to the oil, and they settle when you stop using it.

Essential oils as a group can cause allergy, and bog myrtle oil is no exception. Patch testing a small area first is the usual way people check.

The serious concern is not a side effect but a hazard: animal studies link the oil to harm in pregnancy. Swallowing essential oil of any kind can also poison, and children are at highest risk.

Reporting on this plant is patchy. Rare harms may simply not have been recorded.

How much Bog myrtle should you take?

• Recommended daily: There is no established amount for bog myrtle, and this page gives none. No health authority has set a safe daily amount for the leaf, the tea or the oil. Oil strength varies a lot between products, so a spoon of one tea is not the same as a spoon of another. Skin repellent products carry their own directions. Those directions come from the maker and the local rules, and they are the figures to read, not anything from this page. The essential oil is never for swallowing, at any amount.
• Best time of day: Time of day only matters for the repellent use. Midges bite most at dawn and dusk, so that is when people apply it. For every other use, there is no evidence that timing changes anything.
• With or without food: Food does not apply to skin or cupboard use. If the leaf is taken as a tea, it is bitter and drying, and it sits better with or after food. Taking it on an empty stomach makes stomach upset more likely.
• Time to effect: As a skin repellent, the scent acts at once and fades within a couple of hours, often sooner. For the traditional internal uses, no honest time can be given. These uses have not been tested in people, so it may do nothing at all.
• How long to take it: No safe length of internal use has been worked out, so none can be given. As a skin repellent, it is used for the hours you are outside and washed off afterwards. Repeated daily use on skin raises the chance of an allergic rash. If you are using it for any health reason and nothing has changed after a week or two, there is no reason to keep going.