What Is Estriol, and What Is Estrogen’s Role in Skin Health?

Estriol, estrogen…what exactly is the difference? It can be confusing when so many terms sound similar. So let’s take a step back and start with some basic definitions:

Estrogen: Produced naturally in women’s bodies, there are different forms of estrogen, including estriol and estradiol  

Estriol: Produced in high amounts during pregnancy, it is a less potent form of estrogen than estradiol

Estradiol: It is the most potent form of estrogen and is responsible for fertility and the menstrual cycle 

Topical estriol: The main ingredient in our M4 skincare line, it helps boost collagen, restore moisture, and improve elasticity

Topical estradiol: Used in our vaginal cream, it can provide effective relief for vaginal dryness and itching, and to treat urinary symptoms and painful sex

While estrogen’s primary function is in reproduction, it affects almost every system in our bodies (metabolism, cognitive function, bone strength, and cardiovascular health). And it plays a crucial role in the health of our skin, the body’s largest organ, in multiple ways. 

What Does Estrogen Do?

Here are the main functions of estrogen:

• Produces collagen. This essential protein is found throughout your body in bones, muscles, organs, connective tissues, and skin and its purpose is to keep them all healthy and vital. 

• Helps to heal wounds. When you have a cut or bruise, estrogen kicks in to prevent excessive inflammation and stimulates collagen production, which helps repair tissue and reduce scar formation. 

• Keeps skin hydrated. Estrogen supports the skin barrier function, which increases hyaluronic acid and sebum, helping to amp up moisture levels.

• Increases skin thickness and elasticity. The collagen in estrogen helps keep skin firm, plump, and springy. 

Estrogen in Perimenopause & Menopause

When estrogen levels sharply decline, as they do for women in perimenopause and menopause, so do collagen levels, and the effects of that loss become more pronounced. The skin on our faces, bodies, and vaginas becomes significantly thinner, drier, less elastic, and more wrinkle-prone. In fact, up to 30% of dermal collagen is lost in the first five years after menopause, and decreases by an extra 2.1% every year after. That’s where topical estriol comes in to save the day. 

Estriol, when applied directly to skin, helps to counteract these effects by accelerating collagen production, adding moisture, and improving elasticity. We developed our M4 Face Cream Rx with this in mind. 

The First Prescription-Strength Estriol Cream

Knowing how drastically estrogen loss affects the entire body during perimenopause and menopause, we decided to focus on ways to restore it. Alloy has offered estradiol in the form MHT (Menopausal Hormone Therapy) since we started. Those MHT products provide dramatic relief from the symptoms of menopause. 

Then, in 2023, we were the first company to create a topical cream called M4 Face Cream Rx, a prescription-strength formula that included estriol as a primary ingredient. The results were remarkable, and in 2024 an independent clinical study* showed significant improvements in skin after just 12 weeks:

• 88% improvement in elasticity

• 70% improvement in hydration

• 68% improvement in overall skin health

• 57% improvement in skin texture

*compared to placebo

Read the Full Clinical Study

Next-Generation Skincare Innovations

After the success of M4 Face Cream Rx, we decided to explore more formulations with estriol, and are launching two prescription anti-aging additions: 

• M4 Face Serum Rx with Estriol, Peptides + Hyaluronic Acid restores hydration and elasticity, boosts collagen production, improves firmness, and supports hormonal skin repair for more youthful-looking skin.

• M4 Eye Cream Rx with Estriol + Peptides brightens, tightens, and transforms the delicate eye area. The first of its kind–formulated with 1% estriol and advanced peptides to combat the signs of aging. 

The Results for M4 Eye Cream Rx Are Impressive

In a 2025 independent clinical study, statistically significant improvements* seen in M4 Eye Cream Rx in a 12-week study include up to:

• 25% improvement in wrinkle reduction

• 33% improvement in firmness 

• 40% improvement in elasticity

• 40% improvement in crepiness on eyelids

*Based on expert assessment

And, most importantly, the estriol in all our M4 skincare collection is safe and non-systemic. So you can use M4 skincare alone or in conjunction with MHT, including topical vaginal estradiol. 

Read the Full Clinical Study

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