Her hero product

Biologique Recherche’s P50 1970 toner goes against everything modern “green” beauty obsessives stand for. An active ingredient is phenol, an acid banned from cosmetics in the EU, and the burning sensation leaves skin red and blotchy — but it flies off Rescue Spa’s shelves. “I’ve been using it for 25 years . . . So I’m certainly one of the people who [are] responsible for its popularity,” says Mieloch, who advises using the toner after cleansing and before moisturizing. The solution contains a mixture of exfoliating acids, which buffs away dead skin cells. Other ingredients balance the skin’s pH level and lightly moisturize. “If there’s congestion, it helps you to push everything out and clear it out, rather [than] suppressing it with benzoyl peroxide and things like that,” says Mieloch. “It really encourages your own skin to build a healthy skin.” Concerned about phenol? No need to panic, says dermatologist Dendy Engelman, MD. It has been used for over a century as an antiseptic and hasn’t been found to be carcinogenic. “In certain concentrations, phenol can cause chemical irritation and acute chemical burns,” Engelman tells The Post. “In the amount found in P50, this is not the case and most users tolerate the formulation without issue.” If you’re still concerned, opt for one of the brand’s three phenol-free versions. The toner smells strongly of formaldehyde and can leave skin stinging, but Mieloch says it’s not as abrasive as it seems. “It’s not harsh,” she says. “It’s intense, but actually, it helps to rebuild your healthy skin.” She compares it to funky-smelling and -tasting health foods. “When you drink kombucha, it feels a little weird, but it’s good for you,” she says. “Even lemon — it’s so good for us to drink lemon water, but at first it may be a little intense. [It’s the] same approach with P50.”