In the 1960s, Albert Kligman and James Fulton at the University of Pennsylvania developed tretinoin as an acne treatment. The US FDA approved it in 1971. It is a small, slightly clinical origin for something that now sits in ordinary bathroom cabinets, and it is why the whole retinoid family carries a reputation for being effective and a little demanding at the same time.

Retinol is the gentler branch of that family, and for years we kept it to our faces. The body was an afterthought. DRMTLGY is one of the brands changing that. It was started by Scott Futterman, co-founder and CEO, and Samuel Raoof, co-founder and COO, who cite more than 22 years of formulation experience and an FDA-registered facility in Los Angeles. The brand says its formulas were originally developed for dermatologists and plastic surgeons, and that a board of dermatologists oversees them. I read that as the brand's positioning, not proof, but the line is focused and doesn't sprawl.

The DRMTLGY retinol body lotion is the anchor of the first grid. The brand says it firms, improves elasticity and reduces the look of crepey skin, sun damage and dark spots, and its ingredients include retinol, glycerin, caffeine, ceramide NP, centella asiatica, shea butter and vitamin E. The page does not state the retinol percentage. The brand recommends evening use, SPF 30 or higher if you use it in the morning, and no use during pregnancy or breastfeeding.

The trick is to see the lotion as the start of a small routine. Around it sit the Neck and Décolletage Cream and Peptide Night Cream, the two Needle-less serums, the SmrtSun SPF 45, the Microdermabrasion Scrub and the FacialRX Brightening Moisturizer with vitamin C.

Start with a patch test on your inner arm, and then use the product every third night for two weeks. Body skin is thicker than facial skin, but it can still get irritated, and you learn more from a slow start than from a rash.

Compare formats before comparing claims. Versed's Press Restart Gentle Retinol Body Lotion and Nécessaire's The Body Retinol are the closest in spirit to a plain evening lotion. Josie Maran's Pink Algae Pro-Retinol Body Butter is the richer butter, named for anti-aging and KP, and Sol de Janeiro's Beija Flor Elasti-Cream, which the brand says boosts collagen, is a lotion you will want to use for the scent alone.

Murad's Retinal ReSculpt Firming Body Treatment Cream brings retinal, a cousin of retinol, and StriVectin's Crepe Control Tightening Body Cream goes for the softening-and-tightening angle. Topicals' Slather Exfoliating Body Serum uses retinol and AHAs together, and U Beauty's The SCULPT Arm Compound has retinol and caffeine for the upper arms.

A pairing I like: a retinol body treatment at night on the arms and thighs, then a plain, fragrance-free lotion on the days you skip it.

What I would skip: starting a body retinol the week before a beach holiday. Give the skin a few months to settle first.

One rule for rough, bumpy skin: exfoliate gently and moisturize more than you scrub. KP, the small bumps on upper arms and thighs, tends to get worse when you sand it with a rough scrub.

First Aid Beauty's KP Bump Eraser Body Scrub with 10% AHA is the classic reach. Nécessaire's Body Exfoliant Bar is an in-shower KP treatment you rub on, and cocokind's KP Smoothing Stick is easy to keep by the bed. The INKEY List's Glycolic Acid Exfoliating Body Stick works the same way.

For lotions, Naturium's Urea 5% Body Serum and its Smoother Glycolic Acid Body Lotion divide the job into hydration and exfoliation. Skinfix's KP+ Psoriasis Smoothing Treatment Body Lotion is worth reading the label on before you use it, and Glow Recipe's Watermelon Glow AHA Pink Dream Body Cream is the prettiest of the group, ideal if you want a smoothing routine that feels indulgent.

A pairing I like: an AHA product two or three nights a week and a retinol body lotion on the others, never both on the same night.

What I would skip: acids and a retinol on the same evening, especially if your skin is already stinging. Alternate them.

A habit worth borrowing from the dermatology aisle: put the sunscreen on the body parts you exfoliate and treat. Retinoids and acids make skin more sensitive to sun, so if you use a retinol body lotion, this grid is not optional.

Supergoop's PLAY Everyday Lotion SPF 50 works on face and body, and its PLAY Antioxidant Body Sunscreen Mist SPF 50 is the quick spray for shoulders. Vacation's Classic Lotion SPF 50 has the retro pool-day feel, and its Chardonnay Oil SPF 30 is the glowy one. Shiseido's Ultimate Sun Protector Lotion SPF 60+ is the serious, all-day choice.

Sol de Janeiro's Rio Radiance line is the shimmery end: an SPF 50 Shimmering Body Oil Sunscreen and an SPF 50 Body Spray with niacinamide. Kopari's Golden Sunglaze Body Mist SPF 50 is the golden-hour finish for legs and chest.

A pairing I like: retinol at night, an SPF 50 lotion the next morning on the same areas, and a mist for reapplying at midday.

What I would skip: relying on a shimmering oil alone for a day outdoors. Apply enough of the lotion first, and use the oil as a finish.

I think the DRMTLGY retinol body lotion makes sense for anyone who is already comfortable with retinol on their face and wants to keep going below the jawline. Begin slowly, use it at night, and treat the body sunscreen as part of the routine and not an extra.

The rest is patience. Retinoids reward the people who keep showing up for months, not the ones who chase results in a week. Kligman and Fulton had a lab in Pennsylvania. You have a bottle by the bed and a calendar.

And if you are pregnant, breastfeeding or unsure, ask your doctor before you start. If you want to keep browsing, I also put together The Best Body Lotion Is the One You Reach For Wet and Tanning Lotion Without the Sun.