Nine out of 10 little sisters agree: Big sisters are expert authorities when it comes to discovering cool new stuff first. I read my sister’s books after she finished reading them, I wore her clothes after she outgrew them, and I listened to the music that she played in the car. So when I visited my sister a few weeks ago, I was more than happy to try out a new product that she picked up a Costco: the Karuna exfoliating foot mask.

Preservatives are necessary ingredients in personal care products. Would you want to find mold thriving in your face cleanser (or in anything else you’re applying directly to your skin)? Even so, it’s probably still better to ensure that your skincare and beauty products don’t contain preservatives that are likely to irritate your skin. I didn’t even know that some ingredients were only permitted in “rinse-off” products (like shampoos), until I asked my dad…

If you don’t mind using the same shampoo and conditioner for weeks on end, buying hair care in bulk will save you a lot of time and money. Kirkland Signature (Costco) makes its own brand of color-safe hair care products that describe themselves as “professional salon formulas” that are safe for color-treated hair. I highly recommend buying this pair of hair care products, particularly if you don’t want to think about repurchasing a refill of conditioner or shampoo for…