Occlusion means creating a layer on the skin surface that physically slows water evaporation. Occlusive ingredients form a film that reduces trans-epidermal water loss (TEWL) — one of the oldest and most direct moisturising strategies.
Classic occlusives include mineral oil, paraffin and petrolatum. They are effective at holding water in, but are foreign to skin: they don't join the barrier's own lipid structure, they merely cover it. Some find them heavy.
The modern barrier-friendly approach prefers compatibility over covering. Formulas with skin-identical lipids slow water loss by joining the barrier's natural composition — supporting skin without clogging it. This distinction underpins Zeitschild's philosophy.