Pharmaceutical companies can make no profit from herbs which humans have historically consumed. Instead, they create new molecules. They have a hard time creating molecules that affect only the system they want to affect, therefore there are inevitably side effects.
Nature, evolution, has done a better job at creating beneficial molecules. All life is based on DNA, and molecules that are beneficial in one organism are likely to be beneficial for other organisms, which is why they consume each other for nutrients (not just for energy).
I hypothesize that all too many of these side effects created by pharmaceuticals are allergic in nature. You are taking a fabricated molecule that has never been seen before by human cells. You could be messing with your immune system by creating an allergic reaction to a molecule that has never been in use by any organism. There are no reliable studies for the long term changes at the molecular level to your epigenome, including your immune system, brain function, and aging effects. I believe the age of pharma will be an embarrassment to humanity, much like the former practices of bloodletting and labotomies. You think people aren't like this in the present age? Think of all the Germans that were following Hitler. Actually, Hitler got a lot of his ideas from practices that were the norm in the United States.
“behavioral ethics research suggests that an especially large proportion of the population (in some studies more than 50%) may behave unethically, because their ability to objectively interpret the ethicality of their own behavior is highly limited.” source
It would be wise to perform an allergy test for any drug you might take, just like you would to find out if you have a food allergy.
Pharmaceutical drugs usually have a lot of unwanted side effects. So when your doctor suggests you take a certain drug, just tell them you'd like to first get an allergy test on that drug. There will likely be resistance and excuses towards not doing so, like trying to tell you that side effects are not allergies.
You shouldn't be allergic to any drug you take, so what's the harm of a small test? Never mind that if you chew the pill in your mouth and let it sit for a minute, it leaves a burn on your gums. Maybe the digestion process changes the nature of the molecule, but maybe it doesn't? Your gums are made of cells just like the rest of your body. They test for food allergies by placing the food on your skin, so why shouldn't it be the same for a drug? If I learn more about this, I will add the info here.