It is a trendy osmolyte and compatible solute. It is mainly found in bacteria whilst plants and animals use other compounds for similar tasks. Apart from cosmetics and other dermal products, several pharmaceutical products containing ectoin as active ingredient like nose sprays, eye drops, or lozenges have been popping up in the last few years. These feel ‘comfortable’ but the effect ain’t as good and strong as I expected from marketing claims. Ectoin may have some advantages over other osmolytes such as being less tacky, having a faint anti-allergic and anti-inflammatory activity, and if applied as hypertonic solution won’t sing as unpleasant as salt and even glycerol do.
Maybe one reason for its fame is that it protects from higher heat, pressure, and salinity than other osmolytes and compatible solutes and is hence called an ‘extremolyte’… which is maybe less due to its chemistry rather than the fact that plants and animals couldn’t live under those extreme conditions no matter what even if they were to use ectoin instead of glycerol, glycine betaine, erithritol, taurine, trehalose, proline, or similar compounds.
In my personal opinion, its’ more smoke than fire. Given the high price, my interest in ectoin has faded…