Best for: Weak nails that won't grow

A nail serum can be a lifesaver if you're trying to figure out how to make your nails grow when they're weak and brittle. Like serums for your face, nail serums provide superconcentrated amounts of good-for-you ingredients that absorb quickly.

Try:
Londontown Kur Regenerating Nail Serum, $35, is a vegan, non-toxic serum that contains a blend of moisturizing waxes and oils. They act like a deep conditioning mask for your nails, keeping them nourished and healthy, which promotes nail growth.

Best for: Peeling, weak nails

Cuticle oils and creams do so much more than make your raggedy, ravaged cuticles look as nice as your manicure. Your cuticles protect the growth matrix of your nails. Translation: Healthy, moisturized cuticles equal longer, stronger nails.

Try:
CND SolarOil, $8.50, made with jojoba oil and vitamin E that deeply conditions cuticles and keeps them in tip-top condition. Use every day for best results.

Dior Créme Abricot Fortifying Cream for Nails, $27. This luxe balm has been around since 1963, and has become a cult classic. Apply it at night, and wake up to gorgeous, soft, healthy cuticles.

Best for: Nail biters

One of the trickiest questions to answer is how to make your nails grow when you're an obsessive nail biter. I used to bite my nails, and most of the time I wouldn't even notice I was doing it. Nothing makes you pay attention like a sour, disgusting taste in your mouth. There are many foul-tasting deterrents that can help you quit nail-biting like, well, a bad habit.

To stop nail-biting and make your nails grow, Far also recommends regular manicures. "It is a lot less tempting to bite your nails when they are perfectly polished. Nobody wants to ruin a fresh manicure!" (My advice: book one a few weeks in advance so you have a goal to reach.)

Try:
Mavala Stop, $16.50, a sour concoction that you definitely don't want in your mouth.

Best for: All nails, but especially those that are weak and peeling

Base coats with protective ingredients like keratin and biotin not only elongate the life of your manicure, they also help keep your nails from splitting and peeling -- resulting in longer, healthier nails.

Try:
Nails Inc. NailKale Superfood Base Coat, $15, a nourishing, polish-prolonging base that contains hydrating botanical extracts and nail-strengthening keratin.

Deborah Lippmann Hard Rock Hydrating Hardener, $20, can be used as both a base and a top coat. It was designed to help repair and strengthen nails that have been ravaged by gel nail polish. It contains biotin and a blend of seed oils and leaf extracts.

Best for: Nails that just won't grow

"Nails take an average of 10 to 18 months to grow out. Biotin (aka vitamin B7) helps them grow a little bit faster," says Downie. Biotin can also help strengthen your nails, but keep in mind that it's working on the nails growing, not the nails you can see (because those are technically dead cells), so be patient with results.

Try:
Hum Nutrition Killer Nails, $20, a vegan, gluten-free supplement that you take once a day with food.