From choosing the right moisturizer for your skin type to getting your makeup collection summer ready, finding the right skincare products and treatments can be a challenge. Procuring your beauty arsenal is just the first step, however! We must also consider how and when to use our carefully selected skincare products.

 

While the general rule of applying products from lightest to heaviest still applies (e.g., toner, serum, then moisturizer), a product’s formulation will determine what other products and treatments it can be combined with. Properly combining products can help prevent over-sensitizing your skin – over-sensitized skin may be more vulnerable to irritation and UV damage. Furthermore, understanding how your products work together (or don’t) will help you get the full benefit of their active ingredients.

 

1. Benzoyl peroxide and antioxidants

While the debate over the safety of benzoyl peroxide is never ceasing, BP is undeniably one of the most popular and affordable over-the-counter acne treatments. Benzoyl peroxide is an oxidant that produces phenyl radicals, a type of free-radical that kills acne bacteria.

 

Combining benzoyl peroxide with antioxidants, which fight free radicals, results in both products losing their effectiveness. In other words, the active ingredients cancel each other out. There is one exception, however. Benzoyl peroxide and resveratrol (an antioxidant found in the skin of grapes) do not completely get in each other’s way, making the combo a potent acne-fighter (according to a UCLA study).

 

2. Vitamin C and exfoliating acids alpha hydroxy acid (AHA) and beta hydroxy acid (BHA)

 

A common concern about vitamin C (often listed as “l-ascorbic acid”) and exfoliating acids (such as AHA and BHA) is that the pH of the acids renders vitamin C inactive. Dermatologist Paula Begoun points out that this concern has roots in a 1990 study that was never successfully repeated and argues that layering skincare products with different pH requirements may actually be OK.

 

Even if pH isn’t an issue, dermatologist Joshua Zeichner suggests exfoliating acids may overpower vitamin C because it’s rather unstable. Because the efficacy of combining vitamin C and exfoliating acids is an ongoing debate among skincare specialists, it may be worth it to play it safe and space out your products, morning and night.

 

3. Alpha hydroxy acid (AHA) and water

 

 

AHA is a water-soluble acid, meaning it dissolves in water. For this reason, an AHA-containing cleanser may not be the smartest buy. If your cleanser contains AHA, leave the cleanser on your skin for at least one minute so the product has a chance to do its job (chemically exfoliate skin) before being rinsed off.

 

If you do want to include AHA in your skincare regimen, find and use it in serum form.

 

4. Probiotics and antimicrobials

 

 

Probiotics in topical skincare products are making a big splash – and with good reason. Although research on this treatment is still budding, regular use of topical probiotics has been associated with clearer, less inflamed skin and reduced instances of dermatitis. Probiotics are living bacteria, so we want to be careful about using any products that kill bacteria. Pay extra attention to the bacteria-busting ingredients in your anti-acne products. Common antimicrobials include tea tree oil, sulfur, and benzoyl peroxide. Essential oils containing limonene, a compound present in most citrus oils, also have strong antimicrobial action and shouldn’t be combined with probiotic-infused products.

 

5. Microdermabrasion (PMD) and retinol

 

 

Microdermabrasion (including personal microdermabrasion devices (PMD)) deeply exfoliates skin by using a combination of suction and a fine-grit crystal disc to slough off dead skin cells and improve the appearance of fine lines and hyperpigmentation. This treatment is more abrasive than the typical physical exfoliate (scrub).

 

Therefore it’s wise to avoid the use of retinol, which sensitizes skin, for the week prior to a microdermabrasion treatment. If your skin feels a bit tender after the treatment, continue to avoid retinol-containing products for a few days. Slowly reintroduce retinol into your skincare regime by alternating application days.