Can Botox Injected into the Forehead Go Through and Get into the Bloodstream?

If the injection damages a vein then it can go into your bloodstream, but this is rare. Some patients do experience a mild headache and feel a little "out of it", but it only lasts a day or two.

When symptoms have been attributed, extremely rarely,  to systemic effects, from possible circulatory absorption, the flu-like symptoms or headache these symptoms seemed to resolve after a couple or few days, not much longer. Again, this is very rare. It certainly is not an allergic reaction and you can have further treatments when this one wears off if you're comfortable with that option.

It is very unlikely the botox gets into the general circulation. Even if it does, only a small amount can get there when injected from the forehead and it should not have any systemic effects. It is possible to get a headache from the injection and there have been some isolated reports of flu-like symptoms but those usually go away after several weeks. I would check back with your treating physician to express your concerns.