How do we feel about science these days? On the one hand, most of us rational folks would like to say we believe in it, at least when it comes to engineering, the climate, space, and medicine. But when it comes to squishier things, like the stuff that we put on our faces, we tend to get a little bit suspicious. And then, some of us decide that, rather than trust our skin and hair to chemists mixing up unpronounceable ingredients, we’d rather look back to our witchy ancestors and make our own.

“You know exactly what’s being put into them, so there’s a huge advantage to making your own skin-care products,” says dermatologist and RealSelf contributor Michele Green, M.D.

The thing is, sometimes the old wisdom is spot on, and sometimes it isn’t. “A lot of those natural ingredients are so incredibly allergenic that my patients will frequently come in with insane allergic contact dermatitis,” says Adarsh Vijay Mudgil, M.D.

Yikes. With those pros and cons in mind, we asked Green and Mudgil to help evaluate the ingredients that will help us on our way beautiful skin and hair, and the ones that we’d better just leave in the pantry.

Use With Abandon

Milk and yogurt: Like Queens Elizabeth I and Cleopatra before her, Green loves a good milk bath, and she recommends applying milk directly to the face when you’re experiencing a breakout or dryness. “It really calms down the skin,” she says. Research has shown that cow’s milk helps human skin cells (in a lab, not on living humans) grow. The lactic acid in milk is an alpha hydroxy acid (AHA) that exfoliates, moisturizes, and reduces sun damage in skin.

When that milk is fermented into yogurt, you may get even more benefits, as clinical trials have shown yogurt masks improve skin elasticity, moisture, and brightness.

Oatmeal: Oats contain antioxidants (including some that protect against UV rays), anti-inflammatory molecules, water-holding beta-glucans (sugars), and cleansing saponins. That means scientists and Earth mamas are on the same page about how good it is for the skin. “It’s pretty effective and soothing,” Mudgil says.

The labs have a better handle on how to make colloidal oatmeal, which is ground to super-fine particles that scientific studies have shown to help soothe eczema and other itchy, inflammatory skin conditions as well as plain old dryness. Your at-home recipes will probably call for putting rolled oats in a blender, and you’ll get many of the same benefits. However, if you have celiac, avoid using oats that aren’t gluten-free.

Turmeric: If you don’t mind turning every surface in your home lab yellow, this lovely little root may reward you for your efforts. Studies of topical applications of turmeric, or its active ingredient curcumin, show its effectiveness in treating acne, hair loss, sun damage, psoriasis, and more. “Turmeric has tons of antioxidant properties and is fairly inert,” Mudgil says, and coming from a doctor who sees all those DIY efforts gone wrong, “fairly inert” is high praise.

Argan oil: The Moroccan people, who have been using this nut oil in food, on their hair, and on their skin for centuries, might just know what’s up. Argan oil is packed with vitamin E and squalene (a protective lipid), and it’s been shown to help with skin elasticity and sunspots. “It restores your hair and your skin, and you can put it in a moisturizer or deep conditioning for your hair,” Green says, giving us the go-ahead to scour Pinterest for its best argan oil recipes.

Green and white tea: We’re so relieved to hear that both docs are in favor of using tea in our skin care—there are few remedies as easy and pleasant-smelling as using nice, cold tea bags on our eyes after a rough night. Plus, the pretty tint it can give our lotions and potions makes it all seem like it came from a fancy spa.

“I like tea for the antioxidant properties,” Green says. That’s why tea extracts help protect skin from pollution and the sun. Tea also has anti-inflammatory and antimicrobial properties, which is why it may be effective in treating acne. A few studies have also shown that topical application of caffeine increases the blood flow in skin, which sounds promising.

Try at Your Own Risk

Honey: As much as we absolutely want to believe every word the inimitable Jonathan Van Ness has uttered on Queer Eye, honey masks may not be for everyone. Actually, Green and Mudgil were in disagreement over the safety of lathering it on your face. “It has antioxidants and anti-inflammatory properties, so it soothes irritated skin,” Green says.

Manuka honey from New Zealand has been the most widely hyped, and studies have shown various types of honey have antimicrobial properties. That’s why the ancient practice of using honey to heal wounds has been making a comeback. On the other hand, counters Mudgil, “Propolis can cause allergies, and it’s one of the active ingredients in honey.”

Coconut oil: Every other home hair and skin treatment seems to include coconut oil these days, with good reason. Not only does it feel soft and silky, but it’s also laboratory approved as effective against dry skin and certain strains of bacteria. “It has natural antifungal, natural antibacterial properties, and it’s very absorbent,” Green says.

But both Green and Mudgil raised concerns that putting any kind of oil on the skin can clog pores. Plus, there’s the risk of an underlying allergy being made into a full-blown one because of daily use. “People may have had a subclinical allergy that doesn’t have symptoms for years and years and years and years, and finally, the immune system hits a threshold of tolerance,” Mudgil says.

Try to Avoid

Lemons and other citruses: While the acids in citrus fruits seem like a great way to naturally exfoliate and add vitamin C the skin, Mudgil warns that they also might irritate it and increase sensitivity to the sun. The possible resulting burns are probably not what you were trying for in that home mask. Lemon juice also has a pH around 2, and your skin’s acid mantle has a pH of 4.5-5.5, so lemon juice can really mess that up.

Essential oils: Tea tree, rose, lavender, ylang-ylang… they all smell so good, and so many Pinterest-perfect recipes contain them. But dermatologists are certainly not fans of applying these oils to the skin, again because of their tendency to cause nasty allergic reactions.

“When a patient has a new onset rash on their face—the skin’s really dry and flaky, itchy, and irritated—it’s invariably some new product they’re using, like a $200 serum that probably has some kind of essential oil in it,” Mudgil says.

Not to make enemies of an entire burgeoning industry of home beauty gurus, but some of us would like to avoid dry, flaky rashes. Maybe the key here is to have fun with a DIY treat once in a while but then turn to the experts for our daily care.

Sabrina Rojas Weiss lives in Brooklyn, surrounded by her fellow freelance writers and competitive stroller-pushers. Her work has appeared on Refinery29, Yahoo, MTV News, and The views expressed herein are her own and are meant to be taken with a grain of salt. Follow her on Twitter @shalapitcher.