Marjoram is likely safe in food amounts and possibly safe for most adults when taken by mouth in medicinal amounts for short periods of time.
Marjoram is possibly unsafe when used long-term or when applied to the eye or skin as fresh marjoram. There is some evidence that marjoram could cause cancer if used long-term. Applying fresh marjoram might cause eye or skin irritation.
Special Precautions & Warnings:
Pregnancy and breast-feeding: It is possibly unsafe to use marjoram in medicinal amounts if you are pregnant. It might start your period and that could threaten the pregnancy.
Not enough is known about the safety of using marjoram in medicinal amounts if you are breast-feeding. Stay on the safe side and avoid use.
Children: Do not give marjoram to children in medicinal amounts. It is possibly unsafe for them.
Bleeding disorders: Taking medicinal amounts of marjoram might slow clotting and increase the chances of bruising and bleeding in people with bleeding disorders.
Slow heart rate (bradycardia): Using medicinal amounts of marjoram might slow down the heart beat. This could be a problem in people who already have a slow heart rate.
Allergy to basil, hyssop, lavender, mint, oregano and sage: Marjoram can cause allergic reactions in people allergic to these plants and other members of the Lamiaceae family of plants.
Diabetes: Marjoram might affect blood sugar levels in people with diabetes when used in medicinal amounts. Watch for signs of low blood sugar (hypoglycemia) and monitor your blood sugar carefully if you have diabetes and use marjoram medicinally.
Gastrointestinal tract blockage: Marjoram might cause “congestion” in the intestines when used in medicinal amounts. This might cause problems in people who have a blockage in their intestines.
Ulcers: Marjoram might increase secretions in the stomach and intestines when used in medicinal amounts. There is concern that this could worsen ulcers.
Lung conditions: Marjoram might increase fluid secretions in the lung when used in medicinal amounts. There is concern that this could worsen lung conditions such as asthma or emphysema.
Seizures: There is concern that using medicinal amounts of marjoram might increase the risk of seizures.
Surgery: Taking medicinal amounts of marjoram might increase the risk of bleeding during and after surgery. Stop using marjoram medicinally at least 2 weeks prior to a scheduled surgery.
Urinary tract obstruction: Marjoram might increase secretions in the urinary tract when used in medicinal amounts. There is concern that this could worsen urinary obstruction.