Yarrow, a member of the aster family, is closely related to chrysanthemums and chamomile. It flourishes in a sunny and warm habitat, and is frequently found in meadows and along roadsides, as well as on dry, sunny slopes. It grows as a simple, upright, and hairy stem, usually under 3 feet. Yarrow blooms between June and September. The flowers are typically white, but either pink or pale purple flowers are common in mountain areas. The petals are densely arranged in flattened clusters, and the leaves look like feathers. The plant spreads rapidly. There is substantial genetic variation in the plant's beneficial properties.

The flowers, leaves, and stems of the yarrow plant are used as medicine. Yarrow is collected while in bloom.

Pediatric

There have been no studies to determine whether yarrow is safe for children, so it is not recommended for pediatric use. Talk to your child's health care provider before giving yarrow to a child.

Adult

Ask your provider to help you determine a dose.

The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, you should take herbs with care, under the supervision of a health care provider.

If you are allergic to plants in the aster family (chrysanthemums, daisies, and ragweed), you may be allergic to yarrow, either taken by mouth or applied to the skin.

Yarrow may make your skin more sensitive to sunlight.

Pregnant women should not take yarrow. Its ability to relax the smooth muscle of the uterus could cause miscarriage. At least one study found that yarrow was associated with reduced fetal weight in rats. Other studies have shown an increase in the percentage of abnormal sperm among male rats treated with yarrow extract.

No studies have been done to know whether yarrow is safe in breastfeeding women. If you are nursing, talk to your health care provider before taking yarrow.

Because of the potential for side effects and interactions with medications, you should only take dietary supplements under the supervision of a knowledgeable provider.

Yarrow may interact with the following medications:

Blood-thinning medications

High doses of yarrow may slow down blood clotting. If taken with medications that thin the blood, such as aspirin, clopidogrel (Plavix), and warfarin (Coumadin), it may raise the risk of bleeding.

Lithium

Yarrow may increase the amount of lithium in the body, leading to dangerous levels.

Medications to reduce stomach acid

Because yarrow may increase the production of stomach acid, it can interfere with both over-the-counter and prescription drugs, including:

• Cimetidine (Tagamet)
• Famotidine (Pepcid)
• Ranitidine (Zantac)
• Esomeprazole (Nexium)
• Omeprazole (Prilosec)
• Lansoprazole (Prevacid)

Medications for high blood pressure

Yarrow may lower blood pressure slightly, and could strengthen the effects of prescription drugs taken to lower blood pressure.

Drugs that cause sleepiness

Because yarrow is a mild sedative, it can increase the effects of other drugs you take for anxiety or sleepiness. These include:

• Anticonvulsants, such as phenytoin (Dilantin)
• Barbiturates
• Benzodiazepines, such as alprazolam (Xanax) and diazepam (Valium)
• Drugs for insomnia, such as zolpidem (Ambien), zaleplon (Sonata), eszopiclone (Lunesta), ramelteon (Rozerem)