There's a few, but they are all pretty minor. It doesn't mix well with water (rash), so make sure to put it on right before you go to sleep. It can increase sun sensitivity of your skin, making it easier to have sun burn or additional sun damage, so again, put it on before bed. It can sometimes cause breakouts especially when you start using it, including a red bumpy rash. But after a few weeks, your skin typically adapts to it and the rash goes away.

The tricky part is there's all sorts of people that sell Retinol products but the amount of retinol is OTC. This isn't typically good enough, but you can go to your dermatologist to get a prescription strength that really works, and it's cheap.

FWIW, Adapalene (sold OTC as Differin) is a third generation retinoid that is less irritating than the original formulations.

They're minimal; retinol is usually mixed with a carrier oil or cream in various concentrations and applied topically. I would be surprised if it has an impact on the superficial musculoaponeurotic system (SMAS) referred to in the article, however.

For me it’s uncomfortably dry skin on my cheeks.