although it can be due to reflux or the employment of certain prescriptive antihistamines, it is commonest in people who use their voice heavily across the day or those that are talking in a loud voice for great lengths of time. Powering your voice by way of your chest hole rather than just your throat, mouth, and / or nose, 2. The majority are oblivious of and not using their chest hole as their major sounding board. For ordinary voice use, not using the chest is no problem though your vocal quality will never be very dynamic. This is effective enough to withdraw the allergens in the air significantly so that folks will hardly see them.
It should employ a HEPA filter and likewise have an inner filter. While the HEPA filter will target the allergens in the air this other filter will help to take away odours, mould, and dust.