Asthma Support Group
Asthma is a disease of the human respiratory system where the airways narrow, often in response to a "trigger" such as exposure to an allergen, cold air, exercise, or emotional stress. This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing, which respond to bronchodilators.

Pyunkang-hwan sounds terribly expensive and it was hard to find details, but there are some journal articles (co-written by the man that I think markets it, Hyo-Seok Seo), that begin to break down the ingredients and active principles. I am not sure what to make of some of his statements about curing things, but the science in the journal articles is very interesting and probably harmonious with some of other people's findings?
Quercetin is at your link also but it doesn't seem to do much to me or for me, and I think I may have conflicting reports on how it's supposed to help with allergies?
I am curious about trying some of these - things that stop mucus production might be better than things that dry up mucus?
Pyunkang-hwan (Pyunkang-tang) Regulates Hypersecretion of Pulmonary Mucin from Rats with Sulfur Dioxide-Induced Bronchitis and Production and Gene Expression of MUC5AC Mucin from Human Airway Epithelial Cells
Hyo-Seok Seo , Hyun Jae Lee , Choong Jae Lee
Natural Product Sciences. 2014. Sep, 20(3): 196-201
http://kpubs.org/article/articleMain.kpubs?articleANo=E1HSBY_2014_v20n3_196
Apigenin Inhibits Tumor Necrosis Factor-α-Induced Production and Gene Expression of Mucin through Regulating Nuclear Factor-Kappa B Signaling Pathway in Airway Epithelial Cells
Hyo-Seok Seo, Mohamed Asaduzzaman Sikder, Hyun Jae Lee, Jiho Ryu, and Choong Jae Lee
Biomol Ther (Seoul). 2014 Nov; 22(6): 525–531.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4256032
"Also, apigenin was isolated as the active component from Selaginellae Herba (Selaginella tamariscina Spring, Selaginellaceae), the major medicinal plant of Pyunkang-hwan (Pyunkang-tang), an herbal medicinal preparation used for controlling the hypersecretion of airway mucus observed in bronchitis, tonsiltis and pneumonitis in folk medicine (unpublished data)."
Luteolin inhibited the gene expression, production and secretion of MUC5AC mucin via regulation of nuclear factor kappa B signaling pathway in human airway epithelial cells.
Lee HJ, Seo HS, Ryu J, Yoon YP, Park SH, Lee CJ.
Pulm Pharmacol Ther. 2015 Apr;31:117-22.
https://www.ncbi.nlm.nih.gov/pubmed/25285988
"Luteolin, a flavonoidal compound derived from Lonicera japonica Thunb. and Chrysanthemum indicum L., has been reported to show anti-inflammatory, anti-oxidative and anti-carcinogenic effects... Luteolin inhibited PMA-induced phosphorylation and nuclear translocation of nuclear factor kappa B (NF-κB) p65. This result suggests that luteolin can regulate the secretion, production and gene expression of mucin by acting on airway epithelial cells via regulation of NF-kB signaling pathway."
I'm not sure if resveratrol is part of Pyunkang-hwan but I also found this:
Resveratrol inhibits mucin gene expression, production and secretion from airway epithelial cells.
Lee SY1, Lee HJ, Sikder MA, Shin HD, Kim JH, Chang GT, Seok JH, Lee CJ.
Phytother Res. 2012 Jul;26(7):1082-7.
https://www.ncbi.nlm.nih.gov/pubmed/22213337
"(1) resveratrol inhibited the expression of MUC5AC gene induced by EGF or PMA or TNF-α from NCI-H292 cells; (2) resveratrol also inhibited the production of MUC5AC mucin protein induced by the same inducers from NCI-H292 cells; (3) resveratrol inhibited the activation of NF-κB p65 by TNF-α or PMA in NCI-H292 cells; (4) resveratrol significantly decreased ATP-induced mucin secretion from cultured RTSE cells. This result suggests that resveratrol can regulate mucin gene expression, production and secretion, by directly acting on airway epithelial cells."
In recent years it's seemed that resveratrol might be making my lung troubles worse, even though prior to that I took it for at least several years without it causing any problems I'm aware of. It used to help me feel like I could move around more and do more.