Rehmannia is the most important Chinese herb for disorders of the kidneys and adrenal glands.
It also appears to combat adrenal suppression caused by steroid hormones and has a similar tonic effect on the adrenal cortex as licorice.
Used to combat the symptoms and progression of these illnesses, anti-inflammatory herbs used include rehmannia, Indian sarsaparilla (Hemidesmus indicus) and bupleurum (Bupleurum chinense).
Rehmannia also hinders the breakdown of cortisone products in the body, which lengthens the effect of this herb.
In one study, patients with rheumatoid arthritis were treated with rehmannia and experienced good results, including a reduction of joint pain, swelling, and increased joint movement.
The herb also improved the general symptoms of asthma and urticaria. Mild edema developed in a small percentage of patients which is a similar reaction to that induced by adrenocortical hormones.
In traditional Chinese medicine (TCM) the unprocessed rehmannia root is used to reduce heat in the blood, to nourish yin and promote the production of body fluid. Indications for TCM use include febrile diseases, skin eruptions, and nosebleed.
In Western herbal medicine, rehmannia root extract is looked upon as an adrenal tonic; and is believed to support the cells of the adrenal cortex and pituitary during times of prolonged stress.
Oral doses (10-500 mg/kg) of rehmannia fluid extract had an immune modulating effect in an experimental model.
Rehmannia root could, therefore, be helpful in addressing autoimmune conditions of the adrenals and thyroid.
Unlike liquorice (also an adrenal tonic), rehmannia root is suitable for use in patients with hypertension (high blood pressure).
The herb’s main active principles are iridoid glycosides. Catalpol was the first of these isolated from the herb, and it appears its main function is to stimulate the production of adrenal cortical hormones.
These hormones are anti-inflammatory and explain the use of the herb in treating asthma, skin diseases, and arthritis. Catapol is also used to increase the production of sex hormones and in TCM.