i've seen this interesting post which explains how to easily make a homemade bitters
but, would be possible to make without alcohol for a person who is allergic to alcohol?
how it would be?
It can be done, such as making a glycerite. To do it properly though takes some specialized equipment that you likely would not have. This process would involve extracting the herbs in alcohol, adding the glycerin then vacuum distilling off the alcohol.
An easier thing to do it to take a bitter herb such as gentian root, andrographis, etc. Take a pinch of the herb powder and put it on your tongue. Suck on the powder for 5-10 seconds so the saliva can extract the bitterness then swallow.