All these variables determine the chemical composition of your sebum and how much your skin produces. Our bodies are constantly making observations and reacting to their environments.
Let's take quick look at some of the things that can change how much oil your scalp produces, or its composition. I want us to understand why our scalps can behave differently and why. So you understand why a trip to the desert, or a long car ride during ragweed-blooming season might leave you with an unusually oily scalp. Or why your summertime oily scalp can be dry-flaky in winter (or vice-versa). It's normal for an oily scalp to have many moods and appearances.
Skin-health: Having eczema/atopic dermatitis can reduce the quantity of sebum, or change its composition. On our scalps - eczema could be considered an interchangeable term with seborrheic dermatitis. Not everybody calls it that way. But because I enjoy both - I do! If dry-eczema skin is suddenly exposed to an irritating environment (abrupt change in weather, high concentration of allergens) - that atopic skin may become oily.
Age: Most of us are at our oiliest point in our late teens. Then we tend to hold steady through our 20s, with oil production (particularly for women) decreasing beginning in our 30s. Between ages 50-70 women and men (respectively, based on dominant hormones associated with those genders) begin to experience decreasing sebum production.
The chart below shows you (roughly) how sebum production changes with age. Figures may vary with study, they are derived from this source.
Hormones: Hormones determine sebum volume.
Androgens (male sex hormones) correlate with higher sebum production. This varies greatly among individuals, but that’s the trend.
The week before your period: Women tend to experience greater sebum production, thanks to progesterone.
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| Oil production for men and women (dominated by androgens vs. estrogen/progesterone) |
| over time. Age increases as you look from left to right. Oil production increases as the line rises vertically. |
What happens to oils in the wild: Once sebum is exposed on your scalp - stuff happens. Things that can change the texture and fluidity of the oil. One big change is caused by Malassezia yeasts that normally live on your scalp start to break those oils down. They break down saturated fats. (The oils that contribute to solidity at room temperature). Leaving the fluid lipid byproducts. And a more fluid-feeling, greasy-feeling sebum.
Humidity: Humidity affects sebum volume. The drier the air is, the more oily our skin becomes to prevent dehydration. For example, one simple study measured a significant increase in sebum production when women slept in a room with low humidity (30%) rather than high humidity (70%).
Temperature: In hot weather, sebum production also increases. Or hot indoor environments. If it’s dry and hot, that may be an extra-oily situation. Whereas if it’s dry and cold - like in winter in many places - you may really struggle with the changes in your skin. Dehydration and cool temperatures can have unpredictable effects on sebum composition as well as volume - your scalp may be dry, even flaky from irritation, but it may still be producing oils. They may not be as greasy and noticeable.
Hair density and style: If you have lower-density hair (thin hair), it’s more likely to look oily sooner because there is less hair to “absorb” the oil. If you have straight hair or have styled your hair straight, it has more contact with your scalp and neighboring hairs to easily transfer sebum. The more compact your hairstyle - the easier to transfer oils.
Get the idea? Your skin may be oily because of you. Genetics, gender, skin conditions, age. Or because of your indoor or outdoor environment. Or a combination of several factors.
And they change in time and space.
Stay tuned for Part 3 - tips and products to manage an oily scalp.
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