Folk beliefs (superstitions has a pejorative connotation) cover all kinds of things, from seeing the face of one’s future husband to scaring away witches. However, not all of these beliefs are silly. Some, especially the ones relating to health, have arisen from trial and error or simple observation.
For example, the Navahos have a prohibition about sweeping their hogans at a certain time of the year. Come to find out the hanta virus is spread in mouse excrement which, at that time of the year, dries up and goes into the air. So what seemed like a superstition actually had a scientific basis. Another such example is willow bark tea for aches and pains. Since willow bark contains the active ingredient found in aspirin, another true belief. And drinking rose hip tea is good for what ails you. Rose hips are a great source of Vitamin C.
Other beliefs, not so much. You can remove warts by rubbing it with a live toad until they are drawn into a toad’s skin. (really!) You will never have arthritis if you wear a ring of dried raw potato on the middle finger of your right hand. You can cure a simple headache by wearing a necklace of corn kernels. You can cure respiratory illnesses by placing the skin of a black cat on the afflicted person’s chest for three days. If you place an ear of corn between a mother and her baby, he will have a long and prosperous life.
Other beliefs I think need some investigation. Wounds will heal much faster if you place cabbage or plantain leaves on the affected area. This one sounds to me like it might actually work. Another is curing sunburn by placing a mash of wet tea leaves on the area. Since tea leaves are full of antioxidants this one may work as well. You can cure diarrhea or colic by drinking a tea made of blackberry leaves. This treatment at least would do no harm. Diarrhea was a killer of babies back then and one of the other treatments of choice was giving them opium.