Reader question: After a while, some products I have used will start breaking me out around my chin. They were noticeably helping at first and then it just stopped. Is it possible that my skin got immune to it? — Lisa Jean Conrad It’s an all-too-familiar situation: You crack into a brand-new serum and it’s love at first application. Infatuated, you use the bottle religiously for several months…only to discover that your skin looks less glowy and not-so-extraordinary as the calendar pages flip. Are you imagining things or have you grown immune to your skincare? While I wish I could answer this question with a simple yes or no, unfortunately the answer is yes and no. To dive into the yes portion, if you’re using topical steroids or antibiotics like erythromycin or clindamycin, then yes, the bacteria on your skin can become resistant. This weird occurrence is called tachyphylaxis, a fancy term for an eventual tolerance to a medication. Long story short, the body can alter the signaling pathways on a molecular level so that the product is no longer effective. But don’t go purging all your products just yet! Tachyphylaxis is actually very uncommon with general skincare and usually only happens with prescribed ingredients used to treat specific conditions like psoriasis and eczema. If you suspect this is the case, Hadley King, MD, a board-certified dermatologist in New York City, has a good tip: “Concomitantly [simultaneously] using benzoyl peroxide in your skincare routine helps to prevent the development of bacterial resistance.” Now, if you’re referring to general skincare products (i.e., vitamin C, retinol, etc.), there are two things that could have happened. The good news is that you haven’t become immune to your skincare. “Products that increase cell turnover, such as hydroxy acids and retinoids, require an adjustment phase during which time some people may experience skin purging. It’s possible that you think a product is helping for a few days, and then once skin purging starts you think that it has stopped working,” says Dr. King. The truth is that you always get the most robust response to a product immediately upon first use. Don’t worry—even if it isn’t as obvious, the product is still doing its job. What’s more, if you’re a serial skincare switcher-upper, you might be using a mix of ingredients that don’t play well together. For example, benzoyl peroxide will oxidize vitamin C and make it less effective. It’s always a good idea to reevaluate your lineup and confirm everything gets along. That way, you can benefit from all the potent actives without worrying about them cancelling each other out, or worse, breaking you out. The most likely case, however, is that your products haven’t changed—your skin has. It’s rare that your products change nature (unless it’s super old, in which case you should toss it), but your skin is constantly changing based on a number of factors: your environment, the season, fluctuating hormones, etc. In other words, the products you need to use will need to change over time. You might want to switch up your skincare as the seasons change—this includes switching from serums to lotions or lotions to creams during the drier winter months, or adding glycolic or salicylic acid right before your period, when your oil production is at its highest. To make your products the most effective they can be, try exfoliating one or two times weekly to shed the layers of dead skin cells and allow the active ingredients in your product to penetrate deeper. Make sure there isn’t anything else in your skincare routine—or lifestyle—that could be breaking you out. And when all else fails, consult a dermatologist. They can help streamline your skincare routine via an individualized approach that best matches whatever your current needs may be.