So what is the right amount? “The goal is consistency and tolerance, not intensity,” said Dr Ho.

1. Vitamin A (retinol and retinoid) 

Optimal concentration: 0.25 – 0.5 per cent for retinol; 0.025 – 0.05 per cent for retinoid, depending on skin type. 

Application: A pea-sized amount for the entire face, twice to three times a week at the start, increasing to nightly if the skin is able to tolerate it. 

Best time: Only at night as retinoids break down under UV and can make skin more sun-sensitive. 

Potential side effects: Retinoid dermatitis (dryness, flaking, redness and a burning sensation) 

2. Vitamin C (L-ascorbic acid, sodium ascorbyl phosphate and magnesium ascorbyl phosphate)

Optimal concentration: Ten to 20 per cent for most skins and 5 to 10 per cent for sensitive skins. Anything above 20 per cent doesn’t necessarily improve efficacy.

Application: A thin, even layer for the face. 

Best time: Mornings to boost your sunscreen’s UV protection and fight daytime free radical damage. 

Potential side effects: Stinging, redness, dryness and even breakouts from overly acidic or high-strength formulations, especially over 20 per cent.

3. Alpha Hydroxy Acids (glycolic acid, lactic acid and citric acid)

Optimal concentration: Five to 10 per cent as a daily leave-on and up to 20 per cent for weekly exfoliating treatments.

Application: A 20-cent coin-sized amount applied in a thin, even layer; avoiding around the eyes and mouth, which can be more sensitive.

Best time: At night as it can increase sun sensitivity during the day. 

Potential side effects: Over-exfoliation can lead to skin tightness, peeling or micro-tears, heightened sensitivity and increased risk of hyperpigmentation. 

4. Beta Hydroxy Acids (salicylic acid)

Optimal concentration: 0.5 to 2 per cent for most skins.

Application: Two to three times a week initially, increasing to daily or every other day. In addition, start at the affected areas (clogged pores and breakouts) or over oilier areas such as the forehead or nose, before extending to the rest of the face. 

Best time: Either morning or night. 

Potential side effects: Excess dryness, irritation and peeling, especially around the nose and mouth. In darker skin tones, it may also trigger post-inflammatory hyperpigmentation. In addition, combining multiple exfoliants, such as BHA with AHA and retinol, can compound irritation risk. 

5. Niacinamide

Optimal concentration: Five per cent, though sensitive skins should opt for 2 to 3 per cent. 

Application: One pump or four to five drops for full-face coverage. 

Best time: Morning and night. 

Potential side effects: While generally well-tolerated, however, too much can over-stimulate the skin and disrupt its natural pH balance. 

Caution: Concentrations above 10 per cent can cause flushing, itching or irritation, especially in sensitive skins. 

6. Hyaluronic Acid 

Optimal concentration: One to 2 per cent. Look for multiple molecular weights of hyaluronic acid for best results. 

Application: One to two pumps onto damp skin to boost hydration effects.

Best time: Twice daily. 

Potential side effects: Though inherently gentle, using too much without proper hydration (that is, sealing with moisturiser after) can paradoxically dehydrate the skin as it’s a humectant that can pull water from the deeper skin layers when skin is dry.

7. PDRN

Optimal concentration: 0.5 to 1 per cent, which translates to 5,000ppm to 10,000ppm.

Application: One pump for the whole face after cleansing and before moisturiser.

Best time: Nightly to support skin repair. Also ideal for post-aesthetic treatment recovery too. 

Potential side effects: Overuse or unregulated concentrations may lead to congestion or temporary breakouts due to its regenerative property. 

5 MORE FACTORS TO CONSIDER TO BOOST SKINCARE EFFICACY