Hai Tong Pi (海桐皮; Hǎi Tóng Pí; Latin: Erythrinae Cortex; English: erythrina bark) in the current pharmacopoeia is the dried bark of the coral tree Erythrina variegata, or the arbor coral tree, of the Fabaceae family — a deciduous tree with conical sharp thorns on its trunk and branches — harvested in summer or autumn, when the bark peels easily, usually used raw after impurities are removed, washed, cut into strips, and dried. It is neutral, bitter, and acrid, enters the Liver and Kidney channels, and its core actions are to dispel wind-damp and unblock the channels, and to stop pain and dry damp for itch. It usually goes into decoctions, light teas, or warm washes. The usual amount is 5–10 g; a home cup of tea uses a milder 3–5 g. It needs no pre-decocting, late addition, or wrapped boiling — soaked half an hour first, then simmered twenty to thirty minutes. External use is a suitable amount of strong decoction, cooled to warm, washed over itchy skin and aching joints.
It is not Wu Jia Pi. Wu Jia Pi (Acanthopanax Bark) is warm, acrid, and bitter, suiting cold-damp bi while also tonifying the liver and kidney and strengthening the tendons and bones; this coral tree bark is neutral, leaning to unblocking channels and stopping pain when there is no clear cold or heat. Heat bi, with red swollen hot joints, is a poor match. Use caution in pregnancy and breastfeeding. Broken, oozing skin lesions should not be washed with it on your own. Blood-deficiency dry itchy skin needs nourishing first, not this drying bark. Anyone allergic to Fabaceae plants should skip it. Do not keep brewing it daily for more than a few days at a stretch.
It is used most often for three patterns:
-
Wind-damp bi — aching heavy joints, worse on rainy days, numbness, limited movement
- Waist-leg soreness from long sitting or standing, calf tightness and cramping
-
Damp skin itch — eczema rashes, scabies, or ringworm with scaling and itching
Bitter, acrid, and neutral, it is not a daily “joint opener” tea to keep brewing. A scattering, drying bark with no wind-damp blockage present consumes fluids and irritates a weak stomach.
When wind-damp blocks the channels of the limbs, or damp-toxin gathers on the skin, aching tight joints and itchy rashes are common. Hai Tong Pi is neutral, bitter, and acrid. It dispels wind-damp, unblocks the channels, dries damp, and stops itch, which is why it appears in Hai Tong Pi Tang (Erythrina Bark Decoction)–type formulas. It unblocks more than it tonifies. A heat-type red swollen joint, or blood-deficiency dry skin, gets worse if more is added.
Hai Tong Pi is not a catch-all joint pain bark. In heat-type bi, with red hot swelling, or in pregnancy, using it alone is a poor match. Raw cut or washed clean, and whether it belongs in a formula, should be decided by a licensed Chinese medicine practitioner after pattern diagnosis.