Flash a before-and-after in front of the eyes of any passerby and you’re likely to get an oooh or an ahhh from the difference that a robust skin-care product can make. Ask the same of someone monitoring daily complexion progress and the results will probably be closer to a shrug. Sure, it’s easy to spot the tell-tale signs that a skin-care regimen isn’t working (read: dryness, irritation, acne), but to decipher those early clues that one is doing its job? That’s all the harder.

Skin-care pros say that to give any product due diligence, you’ve got to use it for 28 days, which is the cycle with which new skin cells form and old ones slough off. “It usually takes 3 to 4 months to evaluate whether a skin-care change is working to improve the overall appearance of the skin,” says Melanie Palm MD, MBA, FAAD, FAACS of Art of Skin, a dermatologist in California. “It takes a full month for the top layer of the skin, the epidermis, to turn over. Three to four cycles of this turnover allows adequate time to demonstrate a qualitative change in the skin.”

Once you’ve given it some time, however, you can make harder decisions on whether or not a specific tube or bottle might be right for you. If that sounds like a long time to wait, well, it is. So, I tapped top experts to hear about the early signs that a skin-care product is a fit. Here’s how to tell.

How to know if your skin-care regimen is working

Let’s get really basic with this: If your skin is happy, your products are doing their job. “You can tell that your skin-care routine is working if your skin is balanced,” says Shani Darden, celebrity facialist and ambassador for Lumity supplements. “Your skin is hydrated, but not oily. And you’re not breaking out.”

More specifically, you’ll know things are benefitting you if your topicals do what they say they’re supposed to, which feels like a no-brainer, but as more and more products become “multitaskers” it isn’t always so straightforward. “If it’s a brightening formulation, lightening of brown spots should occur,” says Dr. Palm. “If the formula targets inflammation, skin will appear less red and more uniformly even in tone. Skin dryness and flakiness is likely to improve.”

This can also come down to knowing exactly what to expect of different ingredients when product claims are less clear. If vitamin C is a hero ingredient, expect for brightening results. Slathering on hyaluronic acid? Expect a more hydrated, plump complexion. Have aloe on hand? Expect for skin to feel soothed and more chilled-out.

Building a skin-care regimen should be a patient process in which you introduce products slowly and gradually into your regimen to see how your complexion reacts to them. If all is well after a month, consider building on to your routine, but always do so gradually. Nothing really deserves a toss-out if there’s no drama on your skin. “If your skin is balanced and happy, you should absolutely stick to that regimen,” recommends Darden. “At that point, if you add something new and experience issues, it’s so much easier to pinpoint what products are causing issues.” It’s like as they say: If it ain’t broke, don’t fix it.

When to ditch a product

Whenever problems start to arise in your complexion, it’s good to question things. “If you’re breaking out, don’t continue to use [that product],” says Darden. But that’s not always the case—it depends on what the product is. “If you’re using a topical medication prescribed by a dermatologist, that’s the only time you should stick with a product that’s making you break out,” she adds. “Sometimes your skin will get worse before it gets better.” If it’s really bad though, check in with your derm.

Also, products like retinol can take a while to work. “For topical acne preparations such as retinoids, occasionally people can breakout three to six weeks into use, but it subsides with continued use,” says Dr. Palm. “Continued, sustained, and worsening acne for a longer period of time could be related to a product being comedogenic.”

When all else fails, check with your dermatologist or an esthetician. “They can provide some meaningful insight on what to add to an existing regimen, and how to provide meaningful seasonal changes for the skin,” says Dr. Palm. “Every individual’s skin is unique, and recommendations for skin care are best done in conjunction with a dermatologist to create a personalized approach to skin-care products.” Because you want your skin care working for you, not against you.

And here’s the truth on whether your skin develops immunity to your skin care. Plus, these are dermatologist-approved picks for night creams and serums that work wonders.