Can Botox in the Forehead Cause a Numb Feeling in the Lips?

Botox will block the signal from nerve to muscle but doesn't block the signal frm skin to nerve in the sensory (pain) pathway.  In addition, treatment of the forehead nerves utilize different nerves from those that supplies sensation to the lip.  Was there treatment such as fillers that you had injected in the lips? Are you getting a fever blister on the lips that can cause strange tingling prior to the eruption of the cold sore? You may want to see a neurologist for an examination.

Botox is a great product for forehead wrinkles.  It works on the neuromuscular receptor site and blocks the message from the nerve to the muscle fibers to fire.  It should have a minnimal effect on sensory nerves.  I have had a few patients that felt numb on the forehead after injections for a few days/weeks afterwards.  There is not a anatomic reason to have numbness of the lips from injections to the forehead.   

Presumably this is your first BOTOX treatment.  It is understandable to be a little anxious about the treatment.  Hyperventilating occurs when we are nervous.  We breath just a little too fast.  This blows off CO2 in the blood.  You may not even be aware of this.  This causese tingling and numbness in the fingers and lips.  Your GP can confirm this by using a capnograph if they have one, or more painfully, a blood gas.  My advice is try to relax about your treatment and I suspect that your symptoms will resolve.