You need to be extremely careful when using concealers.
Even if you're not "purposely" or consciously inhaling the fibres, you still do inhale some.
Even if you hold your breath, you still do inhale some fibres.
After you shake the fibres out of the can, then sit (are suspended) in the air, and you will breath them in almost guaranteed.
If you continue using Toppik or any other concealer over time, this could cause lung disease; lung diseases cause increased risk of respiratory infections (like pneumonias) and could ultimately shorten life span and quality of life.
Fibers accumulate along the respiratory tract and could deposit in the alveoli. Your body has mechanisms to defend itself (like mucus and cilia), but over time it will cause damage to the lungs.
(I am in the medical field)
EVERYONE who uses concealers should wear a mask - I am not kidding - I do this myself.
You could buy a pack of masks from any hardware (or similar) store for very cheap.
This could, no joke, have long term effects on your health and life span - it's worth the investment for only a couple of dollars.
Concealers have not been around long enough to see their long term effects on health, but their are other journal published cases of people who have been exposed to fibres over long periods of times (e.g. cotton fibres in the workplace), and these people get lung disease. Again, lung diseases make it difficult to breath (dyspnea), highly increase risk of infections, and increase hospitalizations, and decrease lifespan.
I have absolutely no affiliation with the "mask industry", but am telling you this out of the goodness of my heart (you could buy any brand or company of mask you want - but make sure it's high grade N95 type which seals all around the mouth and protects from fibres like those in concealers)
Moreover, you should wear some sort of eye protector. The fibres could accumulate on the conjunctiva of your eyes. This is not something you'd notice, and again, the body has mechanisms to clean the fibres away (via the liquid of tears) but over time this could certainly be dangerous, and cause eye damage.
I use protective goggles and a N95 mask when I use my concealer.
If you have been or are planning to use a concealer for more than a couple of weeks, using a mask could literally have positive long term effects on your health, quality of life, and survival. I am not kidding by any means, and I could send you published, scientific, journal articles if interested.
This is actually a serious danger that is not at all discussed, and only realized it when I started using concealers myself recently. I'm in the medical field (do not want to disclose any specific info for sake of anonymity), but I am writing about this out of the goodness of my heart. Hope you take something useful from it.
Let me know if you have any questions - I'd be happy to help and give you more specifics on what kind of mask, etc.!