Sweet gale / bog myrtle (bath herb, whisk additive)

What is Sweet gale / bog myrtle (bath herb, whisk additive)?

Sweet gale, also called bog myrtle, is a small shrub of northern bogs. Its leaves and twigs smell sweet and resinous. In Nordic bath use, you add them to the water or to a sauna whisk.

The names tell you where it belongs. It is suomyrtti in Finland, pors in Sweden and Norway, and mjaðarlyng in Iceland.

This is a scent and bath herb, not a medicine. Dried leafy stems are sold loose. Shops also sell the essential oil and scented soap.

Here is the honest verdict. Human evidence is very thin. Only one use has been tested in people: the oil on skin to keep midges away.

For bathing, aches, sleep or skin trouble, there are no trials. Long traditional use is not proof that a remedy works. It is also not proof that it is safe.

One point matters more than the rest. Old texts used this plant to bring on a late period. Animal work on one of its oil compounds supports that worry, so pregnancy is a firm no.

How does Sweet gale / bog myrtle (bath herb, whisk additive) work?

Most of what you notice is the scent and the heat. The leaves hold a fragrant oil. Warm water and steam push that oil into the air.

Terpenes (the fragrant parts of the oil) are the main actors. In lab tests, oils like these slow some bacteria and fungi. Whether that happens on your skin in a bath has not been shown.

The insect effect has more behind it. In small field tests, the oil on skin cut the number of midge bites. Protection faded faster than with DEET.

Claims about aching muscles are hard to pin on the herb. A hot sauna relaxes muscles on its own. No study has split the herb from the heat.

There is no good reason to think much of the plant gets into your blood from a bath. Skin and steam contact is the usual route. The oil taken by mouth is a different matter, and it has not been tested for safety in people.

What forms does Sweet gale / bog myrtle (bath herb, whisk additive) come in?

You will meet bog myrtle in a few simple forms.

- Dried leafy sprigs, sold loose for bath water or steam water - Fresh or dried twigs bound into a sauna whisk with birch - A bath bag or sachet you steep like a large tea bag - Essential oil, sold for scent, soap-making and insect repellent - Soaps, bath salts and skin oils that list it as a fragrance - Dried leaf sold for brewing old-style gruit ale, where local rules allow

The whisk and the bath bag are the common Nordic uses. Both are low-strength, short-contact ways to use the plant.

The essential oil is the strongest form by far. It is meant for the skin in dilute form, or for scenting a room. It is not a drink.

Where it comes from:

Bog myrtle has a long record across the north. Brewers used it in gruit ale for centuries before hops took over. The Icelandic name mjaðarlyng points to mead.

In Finland, sprigs were bound into the sauna whisk along with birch. Bathers valued the sharp, sweet smell in the steam.

Farm and croft households rubbed the leaves on skin against midges and gnats. Dried bunches went into linen chests to keep moths out.

Folk healers used warm washes for sore skin and tired limbs. The plant was also reputed to bring on a late period. Old herbals warned pregnant women to keep away from it.

What does Sweet gale / bog myrtle (bath herb, whisk additive) help with?

• Keeping midges and gnats off skin: This is the only use with real human testing. In small field tests, dilute bog myrtle oil on skin reduced midge bites. Protection was shorter than with DEET. The tests were small and not all were well controlled. Treat it as promising, not settled. Dried leaves in a bath will not repel anything on a walk.
• Scenting a sauna whisk, steam water or bath: This works in the plain sense that it smells strong and pleasant. That is the long-standing Nordic use. No trial has looked at mood, sleep or stress from bog myrtle steam. If you enjoy the smell, that is a fair reason to use it. It is not a treatment.
• Traditional wash for aching muscles after heat: Folk practice paired the herb with heat and a whisk for stiff limbs. No human study backs the herb itself. Heat, water and gentle slapping with a whisk account for much of what people feel. Any extra effect from bog myrtle is unproven.
• Traditional wash for itchy or sore skin: Washes were used in folk practice for rough, itchy skin. The tannins are astringent, which can feel tightening. In lab tests, the oil slows some bacteria and fungi. Whether that helps real skin problems has not been shown. Strong washes can irritate instead of soothe.
• Keeping moths out of stored clothes and linen: Dried bunches were a standard household moth deterrent in the north. The scent is the reason. There is little modern testing on fabric pests for this plant. It is a low-risk household habit, not proof of pest control.
• Flavouring old-style ale and mead: This is history and craft brewing, not health. Bog myrtle was a core gruit herb before hops. Folklore says the ale was more heady. That has never been measured. Some countries limit bog myrtle in food and drink, so check your local rules.

Which foods are rich in Sweet gale / bog myrtle (bath herb, whisk additive)?

Bog myrtle is not a nutrient and not a normal food. Historically the leaves flavoured gruit ale and mead, and small amounts were used as a cooking spice in the north. Some countries limit its use as a food flavouring, so rules differ by place.

What are the side effects of Sweet gale / bog myrtle (bath herb, whisk additive)?

• Redness, itching or stinging where the herb or oil touches skin
• Allergic rash, which can spread beyond the contact area
• Eye stinging if oil or steam water splashes in
• Headache or a blocked, stuffy feeling from strong steam
• Coughing or chest tightness in people with sensitive airways
• Dizziness or faintness from the hot bath or sauna itself
• Dry, tight skin after repeated strong washes

Good to know:

Most reactions are skin reactions, and they are usually mild. They settle once you rinse off and stop using it.

The serious risks sit elsewhere. Pregnancy is the main one, and swallowing the essential oil is the other. Both are avoidable.

If you have never used it, try a small patch of skin first and wait a day.

How much Sweet gale / bog myrtle (bath herb, whisk additive) should you take?

• Recommended daily: Bath herb labels usually suggest a handful of dried stems per bath, or a few sprigs tied into a whisk. Essential oil labels usually give a few drops in a carrier oil or in a full bath, never neat on skin. This page gives no amount to take by mouth. No safe internal amount has been set for bog myrtle. The essential oil should never be swallowed. Treat any label figure as a product instruction, not personal advice. If you are unsure, ask a pharmacist.
• Best time of day: Time of day does not change anything about the plant. Many people use it in an evening sauna or bath, simply because that is when they bathe. A hot bath late in the evening can help some people wind down, with or without the herb.
• With or without food: Food does not come into it. This is a bath, steam and skin herb. Do not drink bath water or steam water that has held it. Do not swallow the essential oil. If you eat or drink anything flavoured with bog myrtle, treat it as a food and follow local food rules.
• Time to effect: The smell is there as soon as the hot water hits the leaves. As a skin repellent, dilute oil starts working at once. In field tests, the effect wore off within a couple of hours. For aches, sleep or skin, it may do nothing at all. No trial has shown a health effect from bathing with it.
• How long to take it: There is no tested course length, because there are no trials of bath or sauna use. In practice it is used now and then, for a single bath or sauna session. Nothing supports daily use over weeks. Stop using it if your skin reddens, itches or stings.