Proponents claim that CBD oil can treat a wide variety of health problems, including:
The tricky part is calculating the exact amount of CBD per milliliter of oil. Some tinctures have concentrations of 1,500 mg per 30 mL, while others have 3,000 mg per mL (or more).
Part of this response could be explained by the way that CBD acts in the brain. In low doses, CBD may act as an agonist to several receptor sites, meaning it acts similarly to surrounding molecules that normally bind to the receptor, enhancing the signalling of those receptor sites. At higher doses, however, too much activity at the receptor site can lead to an opposite effect, negating the beneficial effects of CBD.
Outside of these two disorders, CBD’s effectiveness in treating seizures is uncertain. Even with Epidiolex, it is uncertain whether the anti-seizure effects can be attributed to CBD or some other factor.
CBD oil can interact with certain medications, including some drugs used to treat epilepsy. CBD inhibits an enzyme called cytochrome P450 (CYP450), which metabolizes certain drugs. By interfering with CYP450, CBD may either increase the toxicity or decrease the effectiveness of these drugs.
Oral-mucosal drugs are absorbed directly into the blood vessels in the mouth and under the tongue. If sprayed under the tongue, the patient should try to wait at least one minute before swallowing (see Accidental Ingestion below.) Effects usually start after 15-30 minutes and peak around an hour and a half after administration. For consistency, it is best to avoid eating immediately before or after using a tincture. 
When drugs are inhaled through the lungs, they are sent to the brain before getting metabolized by the liver. This makes inhalation the fastest method for administering cannabis. Usually, between 20-30% of the phytocannabinoids like THC and CBD are absorbed this way. The heat from either smoking or vaporizing cannabis converts the acid cannabinoids into their neutral forms.
Inhalation: Smoking and Vaping
Topicals and rubs are one of the more common kinds of cannabis products. They can be used effectively for skin or joint issues, but will not be absorbed into the bloodstream. The presence of terpenes or non-intoxicating acid cannabinoids ( THCA and CBDA ) seem to increase skin permeation, but still not enough to get it into the blood. Large concentrations of terpenes in topical products may irritate and damage the skin.
Oral mucosal tinctures usually come in one of two forms: an under-the-tongue spray or a dropper with a marking at a specific volume (usually 0.5 ml or 1.0 ml). This allows for consistent, measurable dosing. Pay close attention to the labels on these products. Products should be labeled with the dose of cannabinoids per spray or per ml.
The process of solubilzing CBD and/or THC can reverse over time, so groups developing water-soluble formulations need to ensure the stability of their product. On the whole, ingesting water-soluble cannabinoids shouldn’t be much different than ingesting an edible, though the former may turn out to be faster acting and a bit more potent.