★☆☆☆☆
After doing extensive research in scientific papers, I am pretty certain that the observed effects of GSE are not due to it but to added synthetic microbicides. One of those was always present when GSE was analyzed, whereas no verifiably beneficial compounds could be found by simply analyzing extracts produced without those microbicides. More to the point, the specific synthetic microbicide present changed over time, with some falling out of favor over the past 25+ years.
Please read these statements by the American Botanical Council and see the studies:
and
https://pubmed.ncbi.nlm.nih.gov/9037863/
and
Grapefruit Seed Extract
★☆☆☆☆
I bought grapefruit seed extract (one that is recommended in blogs in Germany) because of positive comments here and I am using it now for 1 week. I have a chronic sinusitis for around 20 years and I have been operated three times on my sinuses. Unluckily, I couldn't see any benefit of the grapefruit seed extract nor for my sinusitis neither for anything else. I drink it with water (20 drops in 1 glass 2 times per day). Since three days I use it also as nose spray. I mixed 10 drops in 20 ml water and spray it three times a day. But using it as nose spray irritated my nose and I feel more bad than before using it. I will stop using it.