La Roche-Posay Toleriane Double Repair UV SPF Moisturizer for Face, Daily Facial Moisturizer

What is lactic acid and who should use it?

Lactic acid is a gentle AHA derived from milk that exfoliates the skin's surface while also acting as a humectant to attract moisture. Its larger molecular size means it penetrates less deeply than glycolic acid, resulting in a milder exfoliation with less risk of irritation. It is an excellent choice for dry, sensitive, or beginner skin types, and is particularly effective for improving texture and mild hyperpigmentation.

What is squalane and is it good for oily skin?

Squalane is a lightweight, stable plant-derived oil most often from sugarcane or olives that closely mimics the skin's own sebum. It provides moisture and softness without clogging pores, making it non-comedogenic and suitable for all skin types including oily and acne-prone. Oily skin often benefits from squalane because it can help regulate sebum production by signaling that the skin is already adequately moisturized.

Does pH matter when layering skincare products?

Yes, pH is relevant for certain actives. Vitamin C (L-ascorbic acid) requires a low pH below 3.5 to be effective, and AHAs/BHAs work best at pH 3–4. Applying these after a high-pH toner or essence can reduce their efficacy. Wait one to two minutes between applying a low-pH active and a higher-pH product to allow the skin's pH to stabilize. For most moisturizers and serums at neutral pH, order by texture is sufficient.

What is azelaic acid and what does it treat?

Azelaic acid is a naturally occurring dicarboxylic acid found in grains that has antimicrobial, anti-inflammatory, and melanin-inhibiting properties. It effectively treats acne, rosacea, and hyperpigmentation including melasma, making it unusually versatile. It is available at 10% concentration over the counter and 15–20% by prescription. Unlike retinol or AHAs, azelaic acid is considered safe during pregnancy and is well-tolerated by sensitive skin.