I think, in general, they are probably not harmful and may in fact be beneficial, but I really look into the company's manufacturing practices and ethics. Anyone can claim their products are "natural" or "organic" or "safe" but not have to substantiate it. It also matters where the products are manufactured - a lot of products like this are made by 1 or 2 companies, and then a whole bunch of sellers put their own label on them. Several companies have been written up by the FDA (doTerra and another one) because their consultants made unsubstantiated health claims re oils and diseases.
Based on my work in food science, I'm also suspicious of a "quick fix" or any company that has you buy a whole bunch of different things - take this for headaches and that for menstrual issues, this for colds/flu and that for stress. Biology, epigenetics and cellular nutrition don't work that way. Anything that has you only treating the symptom and not doing a comprehensive approach for prevention is probably not the best use of the consumer's money. I think you have to evaluate the latest fads and see which ones really have staying power and a scientific basis for their claims.