I reckon the use of concealers is slightly different to treatments like minoxidil and finasteride... That's something I wouldn't really tell anyone if I used it. It's more of a day-to-day quick fix, much like wearing a piece.
Keeping it from your wife or long term partner is another thing though. This is the person you are meant to share a profound understanding with, and you'd think if there's anyone you could tell, it would be them...
If you did keep it from your wife, you'd wanna make damn sure she never found out - I know I'd be slightly disappointed if my girlfriend suddenly announced that she's been using botox or having collagen injections or something like that without ever telling me. Even worse would be if I found out by myself...
I tell my girl everything about my treatments and she is very supportive. We often joke about it, while I'm chasing her around the room with my eye dropper full of "hair"... I swear she's under the impression that if even a drop of minoxidil touches her skin she'll sprout tufts of uncontrollable hair in a matter of hours (if only!)
I really wish more women were as supportive and understanding as she is. Then again, her dad's pretty much bald, and she has a brother who has also started losing hair slightly...
As far as telling my mates about treatments, I actually don't mind at all now. Most of them would be understanding, and if they did think it was strange, I would simply explain the situation in a way they would see the importance. Most of them are pretty health-conscious and into keeping up appearances so I couldn't see them taking it the wrong way.
