1.5% is a very high over-the-counter dose, and Peter Thomas Roth discloses it. That combination — high and honest — is rare. Most brands that go this strong hide behind a "complex."
Fragrance-free, in an opaque pump bottle rather than a jar. The packaging is right.
The ingredient list is short — twelve items — which means little to react to beyond the retinol itself.
Encapsulation is a real technology, and it does two things: it protects the retinol from air and light, and it slows the release, which flattens the irritation peak. It does not make retinol stronger.
Irritation is expected, not a sign it is "working." Redness, flaking and stinging in the first weeks are common with any real retinoid. Start twice a week and build up. If it is still angry after a few weeks, the dose is too high for you.