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 completely 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, then go about 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 pretty much any other problem you can imagine.
The first school of thought is actually 100% correct. Oil pulling is a primitive form of mouthwash, similar to how chewing on certain sticks acted to improve oral health before the introduction of toothpaste and toothbrushes. Medical studies have shown that there is a statistically significant reduction in the amount of certain types of bacteria in the mouth after performing the oil pulling technique. However, it is less effective than spending 2 minutes with a traditional antiseptic mouthwash. It also has the rare chance of causing pneumonia if the oil is accidentally inhaled .
If mouthwash was difficult to find, I could understand using the oil pulling technique. However, just stick to traditional mouthwash. It’s been engineered to work better.
The second school of thought is what concerns me the most. There is absolutely 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 even specify which “toxins” that the oil pulling method was supposed to draw out. In fact, 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 a little bit of common woo. It’s true that gingivitis can lead to other, more serious medical complications but 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 definitely 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.