Citrus medica.  香櫞 Xiāng yuán, Fo shou   Citron Family: Rutaceae   
PART USED: The citron is unlike the more common citrus species, such as the lemon or orange. While those more popular fruits are peeled to consume their pulpy and juicy segments, the citron's pulp is dry, containing a small quantity of insipid juice, if any. The main content of a citron fruit is the thick white rind, which adheres to the segments, and cannot be separated from them easily.
Nature: Warm    FLAVOR: Pungent, bitter, sour.
FUNCTIONS
1. Promote flow of Energy, relieve energy congestion, transform sputum.[1]
2. Expand middle region.[1]
INDICATIONS
1. Congested chest. Nausea, cough with abundant sputum. Chest pain, abdominal swelling, belching.[1]
COMBINATIONS
- Liver Qi Stagnation: Spreads the Liver Qi and regulates the Stomach Cyperus & Peony- Shu gan wan. 
PREPARATIONS:  Decoction.  Dry fruit  3-9 g.[1]

References
Inner Path can not take any responsibility for any adverse effects from the use of plants. Always seek advice from a professional before using a plant medicinally.
Research

Effect of a traditional syrup from Citrus medica L. fruit juice on migraine headache: A randomized double blind placebo controlled clinical trial.
Jafarpour M, Yousefi G, Hamedi A, Shariat A, Salehi A, Heydari M.
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE:
In Persian ethnomedicine several herbal remedies and functional foods have been used to treat migraine headache which are mostly summarized in Qarabadin-e-kabir (Aghili-Shirazi MH, 1773). One of them is Citron syrup (Sharbat-e-Balang) containing edible Citrus medica L. fruit juice and sugar. The present study was designed to assess the efficacy and safety of Citron syrup on patients with migraine headache.
MATERIALS AND METHODS:
Citron syrup was prepared as described in Qarabadin-e-kabir. In this double blind randomized placebo-controlled clinical trial, ninety patients with migraine headache were allocated to three parallel groups (Citron syrup, propranolol or placebo). Patients received 15ml of Citron syrup, placebo syrup or 20mg of propranolol tablet three times daily after a meal for 4 weeks. Primary outcomes were obtained from three measures: the frequency (per month), mean duration (hour) and mean intensity (visual analogue scale "VAS" 0-10 score) of headache attacks evaluated prior to and following 4 weeks of the intervention.
RESULTS:
Citron syrup was superior to placebo in reduction of headache attacks intensity (P<0.01) and duration (p<0.0001) and as effective as propranolol in patients with migraine headache (P>0.05). However, unlike propranolol, Citron syrup could not significantly reduce the frequency of attacks compared to placebo. No indication of any serious side effects from Citron syrup was observed.
CONCLUSION:
According to obtained results, Citron syrup as a traditional Persian remedy can be suggested as an effective treatment for decreasing pain intensity and duration of attacks in migraine headache and the effectiveness is comparable to propranolol. However, the syrup did not show significant effect on frequency of attacks.
PMID: 26721220 DOI: 10.1016/j.jep.2015.12.040  J Ethnopharmacol. 2016 Feb 17;179:170-6. doi: 10.1016/j.jep.2015.12.040. Epub 2015 Dec 22. ncbi.nlm.nih.gov