Ku Xing Ren (苦杏仁) — TCM Bitter Apricot Kernel for Cough, Wheezing & Constipation

At a Glance

Herb: Ku Xing Ren
Chinese name: 苦杏仁 (Kǔ Xìng Rén)
Latin name: Armeniacae Semen Amarum
Nature: Slightly Warm
Taste: Bitter
Meridian: Lung / Large Intestine
Category: Herbs that Transform Phlegm and Stop Coughing
Introduction: Ku Xing Ren (苦杏仁) is the dried ripe seed of Prunus armeniaca L. var. ansu Maxim. (apricot), P. sibirica L., P. mandshurica (Maxim.) Koehne, or P. armeniaca L., stone fruit trees in the rose family (Rosaceae) cultivated throughout northern China. Documented in the Shennong Bencao Jing, it is the principal herb for directing Lung Qi downward, stopping cough, and calming wheezing — applicable to virtually all patterns of cough and dyspnea when combined with appropriate pattern-specific herbs. Amygdalin (苦杏苷) is hydrolyzed to hydrocyanic acid (prussic acid) in vivo, which at therapeutic doses suppresses the medullary cough center and has a mild bronchodilating effect; at excessive doses it causes cyanide toxicity — making dosage precision essential. Sweet almond (甜杏仁, Tian Xing Ren) is lower in amygdalin and used primarily as a food-medicine to moisten the Lung and intestines with less cough-suppressing potency.

Wind-Cold cough: combined with Ma Huang, Gui Zhi in Ma Huang Tang
Wind-Heat cough: combined with Sang Ye, Ju Hua in Sang Ju Yin
Lung-Heat cough with wheezing: combined with Shi Gao, Ma Huang in Ma Xing Shi Gan Tang
Dry Lung cough from autumn dryness: combined with Sang Ye, Sha Shen in Sang Xing Tang
Constipation from Lung-Large Intestine dryness: combined with Bai Zi Ren, Huo Ma Ren

Dosage: 5–10 g in decoction; crush before adding to decoction
Toxic in overdose — do NOT exceed 10 g; do NOT use raw unprocessed seeds in large quantities; children are especially sensitive (3–5 raw seeds can be fatal)
Processing (stir-frying, blanching) reduces amygdalin content and toxicity
Contraindicated in diarrhea or loose stools — moistening action worsens
Use with caution in infants and young children — lower toxic threshold
Distinguish from Tian Xing Ren (sweet almond): lower amygdalin, gentler, more for food-medicine use; Ku Xing Ren is the standard clinical medicinal

Ma Huang Tang (麻黄汤) — Ku Xing Ren + Ma Huang + Gui Zhi + Zhi Gan Cao; Wind-Cold cough and wheezing
Ma Xing Shi Gan Tang (麻杏石甘汤) — Ku Xing Ren + Ma Huang + Shi Gao + Gan Cao; Lung Heat wheezing
Sang Ju Yin (桑菊饮) — Ku Xing Ren + Sang Ye + Ju Hua + others; Wind-Heat cough
Sang Xing Tang (桑杏汤) — Ku Xing Ren + Sang Ye + Sha Shen + others; autumn dry-Lung cough
Wu Ren Wan (五仁丸) — Ku Xing Ren + Tao Ren + Bai Zi Ren + others; constipation from dryness

Bitter Apricot Kernel (苦杏仁) + Ephedra Herb (麻黄) + Cinnamon Twig (桂枝) + Licorice Root (甘草) → Ma Huang Tang (麻黄汤) — warm acrid release exterior, stop cough and wheezing in cold-type asthma
Bitter Apricot Kernel (苦杏仁) + Ephedra Herb (麻黄) + Gypsum (石膏) + Licorice Root (甘草) → Ma Xing Shi Gan Tang (麻杏石甘汤) — clear lung heat, calm wheezing, treat heat-type asthma and pneumonia
Bitter Apricot Kernel (苦杏仁) + Mulberry Leaf (桑叶) + Chrysanthemum (菊花) → Sang Ju Yin (桑菊饮) — disperse wind-heat, stop cough
Bitter Apricot Kernel (苦杏仁) + Job’s Tears Seed (薏苡仁) + Round Cardamom Seed (白蔻仁) → San Ren Tang (三仁汤) — transform damp-heat, treat damp-warm febrile disease
Bitter Apricot Kernel (苦杏仁) + Hemp Seed (火麻仁) + Immature Bitter Orange (枳实) → Ma Zi Ren Wan (麻子仁丸) — moisten intestine, treat spleen-constrained bowel dryness; safety note: toxic — amygdalin hydrolyzed to HCN (hydrocyanic acid); max dose 10g; processing: scalding (焯水) or stir-frying reduces cyanide content by 40-60%; distinct from Sweet Apricot Kernel (甜杏仁) (Prunus armeniaca var. dulcis) which is a food supplement, not a medicine

Antitussive
- amygdalin → trace HCN — mildly depresses medullary cough center and respiratory centers
- reduces cough frequency and severity
- classic mechanism validated in animal models
Antiasthmatic
- HCN + benzaldehyde — relax bronchial smooth muscle
- reduce bronchospasm
- combined with麻黄 synergistically in麻杏石甘汤 for asthma
Expectorant
- fatty oils — lubricate respiratory mucosa
- reduce secretion viscosity
- improve mucociliary clearance
Laxative
- fatty oils — lubricate intestinal wall
- promote peristalsis
- moisten large intestine
- used for dryness-type constipation
Anti-inflammatory
- amygdalin and metabolites — inhibit COX-2, reduce PGE2
Antitumor
- amygdalin — historically proposed as antitumor agent ‘Laetrile/Vitamin B17’
- current evidence limited and controversial
- some in vitro apoptosis data
Antibacterial
- benzaldehyde — active against S. aureus, E. coli
Analgesic
- mild
toxicity: >30g raw seeds lethal in adults; children more sensitive; treatment: oxygen + sodium thiosulfate

Shen Nong Ben Cao Jing: ‘Governs cough with counterflow and upward-surging qi, thunderous borborygmus, throat impediment; descends qi; facilitates birth and lactation; treats incised wounds, cold heart, and running piglet disorder.’
Ben Cao Gang Mu: ‘Apricot Kernel can disperse and descend; hence it releases the muscles and disperses wind, descends qi and moistens dryness, disperses accumulations — included in formulas for traumatic injury. For treating sores and killing parasites, its toxicity is utilized. For treating wind-cold lung disease, formulas sometimes use it with skin and tip intact, for the purpose of dispersal.’
Ming Yi Bie Lu: ‘Governs fright epilepsy, vexatious heat below the heart, recurring wind qi, epidemic headache; releases the muscles; relieves urgency below the heart; neutralizes dog poison.’
Ben Cao Qiu Zhen: ‘Bitter Apricot Kernel — possessing both the ability to disperse wind-cold and the power to descend qi and eliminate wheezing — because its pungency disperses evil, its bitterness descends qi, its moisture opens constipation, and its warmth promotes and moves phlegm stagnation.’