I have a deep line across my forehead. What treatment would you recommend?

I’d suggest you made an appointment with a great practitioner to get their view on what has caused the line, and what the best way to soften it might be. Most of the horizontal lines on our foreheads are from the way we raise our eyebrows, and the lines settle into place over the years. Because these lines are caused by muscle movement, wrinkle relaxing injections of botulinum toxin A should help soften your line. For lines which are really deep, it may make sense to treat it with a soft kind of hydrating filler, but a skilful practitioner will know just what to do.