When an ingredient best known for its health benefits gains traction for topical uses, too, it causes a slight reconfiguring of everything you thought you knew of it. Take vitamin C, for example. Even those who occasionally dabble in skincare are aware of how important the ingredient — once recognized solely for its spot in your immune-boosting morning OJ — is in a serum.

Collagen is similar in the sense that it's famous for promoting skin and hair health in its pill and powder forms, but it also offers benefits when applied topically. And according to the more than 13,900 Amazon shoppers who've already tested the waters and given it a perfect rating, Elizavecca's CER-100 Collagen Coating Hair Protein Treatment is "magic in a bottle."

Shop now: $7 (Originally $8); amazon.com

But first, let's talk more about collagen. According to New York City-based dermatologist Dr. Debra Jaliman, MD, collagen peptides supply necessary proteins and amino acids that may help you achieve healthier skin and hair.

The best-selling (and TikTok-famous) $7 hair mask creates results so impressive, shoppers even say it's a great alternative to pricier hair care treatments. "I bought Olaplex from Sephora and put it in my hair after bleaching it: no difference," one wrote. "It didn't even feel smooth going onto my hair, but this one smells amazing and already felt smooth and untangled my freshly bleached roots (which would normally be impossible to run my fingers through) and honestly my hair has never felt this smooth and soft after bleaching it and I've been all over platinum for 6+ years. If you care about your hair at all, BUY THIS."

Because the Elizavecca serum isn't a bond repairer like the Olaplex 3 treatment — but instead a protein treatment — its formula is made up of pig collagen and keratin. While the collagen derivative is clearly not vegan, Dr. Jaliman does note that when it comes to collagen products, an animal-based formula like this one ensures you're getting the ingredient in the highest amount.

So if you're curious about the next vitamin-gone-topical product, head to Amazon to try the $7 repair mask reviewers swear by for "silky, smooth, and shiny hair."