Old way is to blow your breath into cup of hand, and let horse smell to get your scent. I do this when meeting a new horse.
As for letting a horse under saddle, or being handled from ground do any of this?
Good way to get skin peeled off shin if standing in wrong place when one strikes.
And, as food for thought? This is very bad manners to let a horse do this when they are under control of human, unless handling a horse to tease.
Horses can understand that when in new group of horses, they are to keep noses to themselves, and their mind on business.
Horses make me a better person.