Something that came across my desk recently was the idea of using coconut oil or other vegetable-based oils as a kind of mouthwash.
The process goes something like this:
You either fill your mouth thoroughly with the oil of your choice or use just a tablespoon, depending on which source you're reading. Next, swish your mouth with the coconut oil for 10-20 minutes. Spit out the oil, rinse with salt water, and do your business.
There are two schools of thought as to what this will do:
1) This will clean your teeth.
2) This will "draw out" toxins in your body and prevent or cure asthma, cancer, diabetes, acne, migraines, and any other problem you can imagine.
The first school of thought is 100% correct. Oil pulling is a primitive form of mouthwash, similar to how chewing on specific sticks improved oral health before introducing toothpaste and toothbrushes. Medical studies have shown a statistically significant reduction in certain types of mouth bacteria after the oil-pulling technique. However, it is less effective than spending 2 minutes with a traditional antiseptic mouthwash. It also has a rare chance of causing pneumonia if the oil is accidentally inhaled .
If mouthwash was challenging to find, I could understand using the oil-pulling technique if mouthwash was difficult to find. However, stick to traditional mouthwash. It's been engineered to work better.
The second school of thought is what concerns me the most. There is no evidence that putting any particular oil in your mouth will cause anything to be "drawn out" of your body. Every website I found could not specify which "toxins" the oil-pulling method was supposed to draw out. The term "toxin" is never elaborated on or explained. Are they talking about heavy metal poisoning? Venom from a spider? Cholesterol? Bad vibes? That lovin' feelin'?
It sounds like someone read an article on osmosis (the process by which chemical concentrations will equalize across a permeable membrane in a fluid) and got it mixed up with some common woo. Gingivitis can indeed lead to other, more serious medical complications. Still, traditional brushing and flossing will be far more effective than swishing your mouth out with random things from the pantry.
Every study has shown no medical impact from oil pulling beyond what would be expected from a mildly effective version of mouthwash .
The process of "film blocking" claimed by oil-pulling adherents where plaque formation is blocked due to ... some unnamed property of the oil... has not been successfully demonstrated.
The idea of a toxin is nebulously defined at best.
The mechanism for any significant whole-body chemical transfer from saliva to oil held in the mouth does not exist.
Summary: Harmless, ineffective junk pseudoscience. It probably won't hurt you (unless you inhale the oil and die of lipoid pneumonia), but you could find better ways to spend your time and money.
 Kim JY, Jung JW, Choi JC, Shin JW, Park IW, Choi BW."Recurrent lipoid pneumonia associated with oil pulling."Int J Tuberc Lung Dis. 2014 Feb;18(2):251-2. doi: 10.5588/ijtld.13.0852.
 Hannig, C., Kirsch, J., Al-Ahmad, A., Kensche, A., Hannig, M., Kümmerer, K. (2013). "Do edible oils reduce bacterial colonization of enamel in situ?". Clinical Oral Investigations 17 (2): 649–658.