Some parts of your skin are dynamic, they change with stress, sleep, hormones and weather. But other characteristics stay relatively steady over time. These are your baseline properties. Knowing them helps you choose products that support your skin, instead of working against it.
Your baseline includes your natural oil balance, hydration patterns and the way your skin tone interacts with ingredients and sun exposure. A 2024 spectroscopy study confirmed that skin surface lipid composition is heterogeneous across the face and contributes directly to barrier function — which is why a single "skin type" rarely captures how different zones of your face actually behave (Assi et al., 2024).
1. T-Zone Oil Balance
The forehead, nose and chin often produce more natural oil. This is the T-zone, and it's perfectly normal for it to look a little shinier than the rest of the face.
Stella observes how much visible oil appears in this region, how pores in the T-zone look compared to other areas, and whether oil increases with heat, workouts or stress.
This helps you understand when to balance oil without stripping it, because oil isn't the enemy. It's part of your skin's protection system.
2. U-Zone Hydration (Cheeks & Jawline)
The cheeks and jawline, the U-zone, usually produce less oil. This area can feel drier or tighter, especially in colder or low-humidity environments.
Combination skin (oily T-zone + drier U-zone) is one of the most common patterns we see.
3. Why Baseline Matters
Your baseline isn't something to "fix." It's something to work with.
Oilier areas benefit from non-comedogenic, lightweight hydration. Drier areas benefit from slower exfoliation and richer moisturisers. Combination skin benefits from adjusting products by region, not one product for everything.
When you understand your baseline, routine decisions become simpler and more intentional.
4. Melanin Content & Tone
Stella also observes how your skin reflects and absorbs light to estimate melanin content. This helps identify your natural tone and how your skin might respond to sun exposure and certain ingredients.
The Bottom Line
Your baseline is your starting point. It sets the foundation for everything that comes next, from hydration strategies to how you introduce actives.
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Dr. Alice Rudd
Cofounder · Skin Science · MBBS Monash UniversityAlice is a Stella co-founder and dermatologist. She trained at Monash University and brings clinical experience to Stella’s measurement framework and scientific boundaries. She also runs Skindepth, a Melbourne dermatology practice.