Can 3 people use one bottle of botox (100 units) for forehead and eye area?

This depends on the number of areas and units being used. I recommend an in-person examination. Best wishes, Dr. Aldo

This ultimately depends on the areas being treated, which will determine the amount needed for each individual. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer

Thank you for your question.It would depend on the number of units used or required to treat each patient. If you used minimal units, it is possible to spread the treatment out to those sites for three people. An in person evaluation would be best to make this determination. Good luck.

I typically inject between 8-15 units in the forehead and 5-10 on each side for the crows. Depending on the severity of the wrinkles, it might work.

That is a very difficult question to answer without doing a face to face consultation. There are patients that may require as little as 20 units and others that need over 60 units. So, it just depends on each individual person. They really need to be evaluated by a trained injector to determine how much will be needed and where it needs to be injected. 

Yes.  The amount is determined by the units needed and there should be no issue getting 3 treatments for this area from one vial

3 people could definitely use just 1 bottle. 32 units is a pretty common dose for my patients, so that puts your right on par to use 1 bottle for 3 patients.
What all of the answers below seem to be missing, which is so critical, is that you need to draw that Botox out into separate syringes. I recommend 10 units per syringe with an insulin needle. Why is that important? 1. Safety - you need to make sure you're not contaminating the bottle 2. Each needle stick dulls the needle of the syringe. Typically, after 5 sticks, you want to change the needle to reduce the discomfort and risk of bruising. Using 10 unit syringes keeps things fresh and comfortable.
Now, will 3 people definitely be able to use just 1 bottle? No, not necessarily. I have a few patients who use 80 units per treatment, and I have many who use 20-30. It just depends on how strong your muscles are, and how relaxed you want them to be. 
A skilled injector can help you relax the muscles without freezing you, and can achieve advanced results, like a browlift. An inexperienced injector can do just the opposite, creating huge problems. This is why I always recommend you see a skilled and experienced injector - someone who injects a lot of Botox (you can tell by their awards from Allergan just how much Botox they are injecting).

Thank you for your inquiry. It is definitely possible if you all require 100 units total together. This amount will be determine by your plastic surgeon according to your muscle activity. Be sure you consult with a board certified plastic surgeon. results will last 3 - 4 months.

Thank you so much for your question.  While everyone seeking Botox should receive an individualized assessment based on their facial needs, the answer to your question is, most likely, "yes".  If you are talking about the eyes as being the area between the eyebrows, also known as the glabellar region, the average amount of Botox needed in this area is 20 units.  For the forehead, somewhere in the range of 8-15 units would be a good treatment.  So, for these two areas, you are looking at around 30 plus units for each person.  If, in the future, you ever want to treat crow's feet on the outer portion of each eye, average treatment would be around 12 units of Botox per eye.  Hope this is helpful!  Wishing you so much bliss on your journey!