If you've ever noticed that the potent anti-aging serum you've been using for ages just isn't what it used to be, you're not going crazy—you may have built up a tolerance to the product. "It is definitely possible to build a tolerance for a product you have consistently used for one year or more," says Miami-based dermatologist Dr. Jegasothy. "This is a commonly-known phenomenon called 'tachyphylaxis,' and it's seen with medication of all sorts, including skincare." The underlying reason is due to the enzymes in your body. Specific ingredients in your products trigger an enzyme to attach itself to a receptor within the skin cell, and once the two are bound, nothing else can enter the receptor. The enzymes become overactive, and with no receptor it can attach itself to, the molecular reactions stop and cause the product becomes less effective.
Unfortunately, there isn't a way to avoid this, and Dr. Jegasothy advises changing up your products every 6 to 8 months, which sort of lines up with the seasonal switch we make to our lineup anyway. "This way, the enzymes increased by the first set of products becomes normalized, and another set that binds to different receptors gets revved up," she explains. You're more likely to encounter this problem with products that claim to build collagen or smooth over your skin cells, but don't lose all hope just yet—Dr. Jegasothy notes that, although an ingredient like vitamin C or retinoids are common across the market, different brands use formulations that activate slightly different enzymes. If you're particular to the effects of a certain ingredient, switching to a different brand could be all you need to do to get your groove back.