What is Biotin?
Biotin is a water-soluble vitamin, also known as vitamin H or vitamin B7. It's sold in many stores along with all of the other vitamins and supplements.
It's marketed for skin, hair and nails because it's said to improve our keratin infrastructure — and keratin is a protein which makes up those three things.
Biotin is naturally-occurring and our bodies produce more than required for cell growth.
What will it do for my Beard?
Honestly, probably not much. From everything we've seen, men that take biotin don't notice any additional benefits to the beard. Some mention lessened shedding of beard hair, but there's not enough evidence to really support it.
Biotin itself is healthy to take, so there's nothing wrong with doing so. It may even provide additional health benefits to those that have deficiencies.
Most people do notice the benefits to their nails, which happens after about three months.
Remember, most methods of trying to improve your hair and beard will take months to see visible results, aside from the method of using minoxidil for your beard, which varies among each individual.
Anecdotally, men have said that after taking biotin for a few weeks they notice lessened hair shedding. This implies that it may help with creating a stronger bond between the follicle and the hair. Since there's no clinical trials, we only have the word of those that have tried the vitamin — and the claims from companies, that sell it, make.
Biotin can also indirectly cause acne, so be aware of that. As it may compete with B5, lowering this vitamin by consuming biotin leads to breakouts in many individuals. For many, this clears up after a while, but is not the case for everyone.
The verdict: At best, I believe biotin works well for those with deficiencies in it, but is likely not going to be helpful for a healthy individual. Don't take biotin in the hopes of improving your beard, but only to improve your overall health.