What is Sweet Gale?

Sweet gale is a small shrub that grows in bogs, fens and wet lake edges. Its leaves smell strongly of resin and spice when you crush them. Most people know it as bog myrtle.

The dried leaves and young shoots were the parts used. Folk healers in North America and northern Europe brewed them as a tea or a skin wash. Brewers used the leaves to flavour and bitter ale long before hops became standard.

Today you will find it as dried leaf, as a tincture, as a strong scented oil, and in a few midge repellent products sold in Scotland.

Here is the honest verdict up front. Human evidence is very thin. The only use tested in people is as a skin repellent for biting flies, and the protection faded faster than standard repellents.

Everything else rests on old custom plus laboratory work. Traditional use is not proof that a plant works. It is also not proof that a plant is safe.

One point matters more than the rest. Sweet gale was used in folk practice to bring on a late period, so it must not be used in pregnancy.

How does Sweet Gale work?

No one has shown how sweet gale acts in the human body, apart from its smell keeping insects away.

The scented oil is the best studied part. In field tests on people, oil-based bog myrtle lotions cut the number of midge bites for a short time. The effect is thought to come from scent compounds that confuse the insect, not from anything entering your blood.

The tea works differently, in theory. The leaves are rich in tannins, which bind proteins in test tubes.

That is the usual reason an astringent herb tastes puckery and was used for loose bowels. Whether it helps your gut is not established.

Some lab work comes from studies of Cree medicinal plants in Canada. In cell and animal studies, sweet gale extracts changed how cells took up sugar.

That is early work only. It does not mean the herb lowers blood sugar in people.

The flavonoids in the leaf mop up free radicals in test tubes. Almost every leafy plant does this. It tells you little about what happens after you drink a cup of tea.

What forms does Sweet Gale come in?

You may meet sweet gale in these forms:

- Dried leaf, loose or in tea bags, for brewing. - Tincture, the leaf steeped in alcohol. - Volatile oil, sold neat or already mixed into a lotion.

- Skin repellent sprays and balms, mostly from Scottish makers. - Brewing herb for gruit ale, used in place of hops. - Dried sprigs for linen drawers, used to keep moths off wool.

The repellent products are the only ones with human testing behind them. The neat oil is strong and is meant for the skin only after mixing, never for swallowing.

There is no standard strength for the tea or the tincture.

Where it comes from:

Sweet gale has a long record in northern folk practice on both sides of the Atlantic.

Native peoples in the northern woods and in eastern Canada used the leaf as a tea and as a wash. Recorded uses included stomach complaints, fevers, itchy skin and sores. Cree communities around James Bay kept it in use into modern times.

Settlers and later American folk healers borrowed the plant. Eclectic physicians of the 1800s worked mostly with its cousin bayberry, Myrica cerifera, and treated sweet gale as a lesser stand-in.

In Britain and Scandinavia the leaf flavoured ale for centuries. It was also hung in rooms and packed with cloth to drive off fleas and moths.

Old herbals also list it for bringing on a delayed period. That use is the reason modern sources treat it as unsafe in pregnancy.

None of this history was written down as it is described here to encourage use at home.

What does Sweet Gale help with?

• Keeping biting midges and flies off the skin: This is the one use with real human testing behind it. Small field studies in Scotland put bog myrtle lotions on volunteers in midge country. Bite counts dropped compared with no treatment. The catch is how long it lasted. Protection faded faster than with standard repellents like DEET. If you are in an area with insect-borne illness, a tested product is the safer choice.
• Upset stomach and loose bowels: Folk healers gave the leaf tea for a sour stomach and for diarrhoea. The reasoning was the tannin content, which is drying and astringent in test tubes. That is a lab finding, not a result in people. No human trial has tested sweet gale for either problem. Diarrhoea that lasts more than a couple of days needs a doctor, not a herb.
• Fevers and colds (as a hot tea): A hot aromatic tea was a standard home measure for chills and head colds. There is no evidence that sweet gale shortens a cold or lowers a fever. Any comfort may come from the warm drink and the strong smell. Treat it as a flavoured tea, not as a treatment.
• Itchy skin and minor sores (as a wash): The cooled tea was dabbed on itchy patches, bites and small sores. In laboratory tests, extracts of the plant slow the growth of some bacteria and fungi. Whether that happens on human skin has not been shown. The oil itself can irritate. Some people develop a rash from it, so a patch test matters.
• Passing more urine: Old sources list sweet gale as a diuretic, meaning a herb that makes you pass more urine. This claim has not been tested in people. Related Myrica species have the opposite worry attached to them, with reports of holding on to salt and water. Do not use it to manage swelling, high blood pressure or heart failure.
• Flavouring beer: Sweet gale bittered and scented ale across northern Europe before hops took over. This is a flavouring use, not a health use. Some brewers have revived it for gruit-style beer. The amounts in beer are small, but pregnancy remains a reason to avoid both the beer and the herb.

What are the side effects of Sweet Gale?

• Nausea or stomach upset from the tea
• A dry, puckery mouth from the tannins
• Skin redness, itching or rash from the oil
• Allergic reaction, including in people sensitive to bayberry or wax myrtle
• Headache from the strong scent
• Vomiting after large amounts

Good to know:

Most reported problems are mild and come from the oil on skin or from strong tea.

The serious concern is not a side effect but a hazard. Sweet gale was used in folk practice to bring on a late period, so it carries a real miscarriage risk in pregnancy.

Because the plant is little studied, rare harms may simply not have been recorded. Stop and seek advice if anything unexpected starts after you begin using it.

How much Sweet Gale should you take?

• Recommended daily: Sweet gale has no tested dose for any internal use, so nothing here is a personal instruction. Labels on dried leaf tea usually describe about 1 to 2 grams of leaf per cup. Tincture labels vary widely and do not agree with each other. Repellent products carry their own directions for how much to apply and how often. Follow the product label, not a herbal source. The neat oil is not for swallowing at any amount.
• Best time of day: Timing does not matter for the tea, because no effect has been pinned down to test. For a skin repellent, the useful time is just before you go out, and again as the product label allows.
• With or without food: If you drink the tea, taking it with or after food is gentler on the stomach. Strong tannin teas on an empty stomach can cause nausea in some people. Keep it well apart from iron tablets, because tannins bind iron in the gut.
• Time to effect: A skin repellent works within minutes and then fades, often faster than a standard repellent. For anything taken by mouth, there is no honest answer. No effect has been confirmed in people, so it may do nothing at all. If you notice nothing, that is a normal outcome rather than a sign to take more.
• How long to take it: No study has tested how long sweet gale can be taken safely. Folk use was short and occasional, for a few days at a time. Open-ended daily use has never been studied and is not supported. If you are using a repellent on skin, use it only while you need it.