I sell several bars with loofah in them, so take this in the spirit it is offered: most people exfoliate their body more often than they need to, and the ones getting the worst results are usually the ones doing it the most.
Exfoliating means removing dead cells from the surface of the skin, either mechanically with something textured or chemically with an acid. Your skin sheds those cells on its own anyway, on a cycle of roughly a month that gets slower with age. Exfoliating hurries the surface along. It does not do anything the skin was not already doing.
Which is worth holding on to, because it sets the ceiling on how much good more of it can possibly do.
How often should you exfoliate your body?
Two or three times a week for most people, on most of the body. Once a week if your skin is dry or reacts easily. Every day only where the skin is thick and loaded — heels, elbows, knees. If you are unsure, start at twice a week and add rather than start daily and cut back, because the second route means noticing you were wrong the uncomfortable way.
Is exfoliating every day bad?
On the body, for most skin, it is not dangerous, it is just pointless past a certain point — you are removing cells that had not finished being useful yet. On a face, on dry skin, or with anything genuinely abrasive, daily is where people get into trouble. The tell is skin that looks shiny and feels tight at the same time.
Is a loofah bad for your skin?
The complaint you have read about is really a complaint about a hanging loofah sponge that never dries between showers, not about loofah as a material. Loofah is a dried gourd, a vegetable, not a plastic mesh. A slice of it set inside a bar of soap dries out with the bar and gets used up with it, which is a different object with a different problem.
What is fair criticism: a big natural sponge scrubbed hard on dry skin is rougher than most bodies want twice a day. Use it on wet skin, with lather, and let the pressure come from the lather rather than from your arm. The bars are in the loofah collection, and the gentlest of them for daily use is the Rose & Calendula Loofah Soap.
How do you know you have overdone it?
Skin that stings when you put on something that never used to sting. A shine that reads as tight rather than as healthy. Patches that stay pink for hours after a shower. Things that used to be fine suddenly are not. None of that requires a diagnosis to act on — it requires stopping for a week and then coming back at half the frequency.
The recovery is boring and it works: nothing textured for seven days, lukewarm water, something rich afterwards, and no new products in the meantime so you can tell what changed.
Does your face follow the same schedule?
No. Less, always, and with something gentler than you would use on a shoulder. Whether a body bar belongs on a face at all is a separate question and I have answered it separately in can you use a body soap on your face. The short version for this page: use the smooth side of the bar, and save the loofah face for below the jaw.
What about heels, elbows and knees?
Those can take daily, and heels in particular need it, because the skin there is thick, has no oil glands under it and is under load all day. That is its own piece: why heels get rough and crack. The general rule holds though — a little, often, on damp skin, is better than a lot, occasionally, on dry skin.
Does it matter when you do it?
At night, if you have a choice, and follow it with something. Exfoliated skin is skin you have just taken a layer off, and the twenty minutes after a shower is when a cream does the most obvious work. If you exfoliate in the morning and then go out in the Florida sun with nothing on, you have chosen the worst available version of this.
How the two halves of the day differ, in general, is the longer story in my day and night routine.
Cosmetic products. Not intended to diagnose, treat, cure or prevent any disease.