1.) I don’t believe there is a straight yes or no answer to this question, as it would depend on the individual and dosage! However, in general, I recommend only taking elderberry if you feel that you are about to get sick, during acute illness, or if you are traveling or have a sick child. For folks who have an autoimmune disease, I don’t believe taking elderberry to prevent illness would cause any harm taken in the short term. If one is taking immunosuppressant medications every day for a serious condition, I am always extra cautious with immunomodulators and tend to avoid them, but I have absolutely given elderberry in the short term for virus prevention.
2.) Keep all cold infusions in the fridge for up to 48 hours. I’d recommend dating it and discarding it after this allotment of time.
3.) Because there is an infused oil in this scrub recipe, and herbal infused oils generally keep for 1 year, I would use this timeline for the scrub as well. Keeping it in the fridge helps as well.
4.) Cloudy lavender-infused oil could indicate the presence of bacteria, so I would recommend throwing it out. You can usually tell by the smell if it has gone rancid. What type of oil did you use? Some oils, like olive oils, can become clumpy/cloudy when they are cold.