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.
Dr. Alice Rudd
Head of Skin Science · MBBS Monash University·6 November 2025·5 min read
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.
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.
Zone-specific care
Knowing your U-zone helps you adjust, lighter textures on the T-zone, richer moisturisers or barrier support on the U-zone. Supporting each region based on what it naturally needs.
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.
Why this matters
Some exfoliants need to be introduced gradually depending on tone. Darker skin tones can be more prone to uneven pigmentation after irritation. Lighter skin tones may show redness more easily. This is about using products in a way that supports your skin's biology, not fights it.
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.
The information in this article is for educational purposes only. Stella is not a medical device and does not diagnose or treat any skin condition. If you have a skin concern, please consult a qualified healthcare professional.
Dr. Alice Rudd
Head of Skin Science · MBBS Monash University
Alice leads the science and dermatology team at Stella. She trained at Monash University and practised in clinical dermatology before joining Stella to develop the metrics framework that underlies the app.
