What Is Castile Soap? Cold-Processed vs. Milled & Prep U’s Sandalwood Bar for Teens
What is Castile Soap?
If you’re searching for a natural, gentle, and effective way to keep your skin clean, you’ve probably come across the term “castile soap.” But what exactly does “castile” mean, and why do so many brands—like Dr. Bronner’s, Dr. Squatch, and Prep U—offer their own take on this classic cleanser?
Castile soap is a type of soap made entirely from plant-based oils. Traditionally, it was made with olive oil in the Castile region of Spain, but today, high-quality castile soaps often use a blend of nourishing oils like coconut, olive, castor, and shea butter. The result? A vegan, cruelty-free, and biodegradable bar that’s free from animal fats, harsh detergents, and synthetic additives.
Unlike most traditional soaps, which can include animal byproducts or synthetic foaming agents, castile soap is prized for its purity and simplicity. It’s gentle enough for sensitive skin, acne-prone teens, and anyone who wants a non-toxic, eco-friendly alternative for their daily routine.
How Is Castile Soap Made? (Cold-Processed vs. Milled)
Not all bar soaps are created equal—even in the world of castile. The method used to make your soap can have a big impact on both its benefits and your overall experience.
Cold-Processed Castile Soap
Cold-processed soap is made by combining plant oils with a natural alkali (like sodium hydroxide) at low temperatures. This gentle process preserves the natural benefits of the oils and essential oils, and allows the soap to cure over several weeks. What you get is a bar that’s rich in natural glycerin, deeply hydrating, and uniquely gentle on skin.
The cold-process method is what gives Prep U’s Sandalwood Castile Soap Bar its artisanal character and skin-loving properties. Each bar is crafted in small batches, ensuring a high-quality, moisturizing clean without the need for synthetic hardeners or detergents.
Milled (or French-Milled/Triple-Milled) Soap
Milled soap, on the other hand, starts as a finished soap (often cold-processed), which is then shredded and re-blended under high pressure—sometimes multiple times. This process creates a denser, longer-lasting bar with a super-smooth texture.
Can a milled soap be castile? Technically, yes—if it’s made from a true castile base (100% plant oils, no animal fats, no synthetic detergents). But always check the ingredients: some commercial milled soaps add fillers or synthetic fragrances that can dilute the gentle, clean benefits of pure castile.
Castile Soap vs. Regular Soap: What’s the Difference?
The main difference comes down to ingredients and skin feel. Regular soaps often use animal fats, sulfates, parabens, or synthetic chemicals that can strip your skin’s natural oils and leave you dry or irritated. Castile soap, by contrast, is made with plant oils, making it naturally moisturizing and suitable for all skin types—including sensitive, acne-prone, and developing teen skin.
When you choose a cold-processed castile bar, you’re choosing a soap that’s kind to your skin and the planet.
How Do the Top Brands Compare? (Dr. Bronner’s, Dr. Squatch, and Prep U)
Dr. Bronner’s: The Castile Soap Pioneer
Dr. Bronner’s is the name most people think of when they hear “castile soap.” Their bars are made with organic oils, certified vegan, and come in a variety of classic scents. They’re beloved for their simplicity, multi-purpose use, and strong eco-activist mission. Dr. Bronner’s is a solid choice for anyone seeking a pure, traditional castile soap.
Dr. Squatch: Bold Scents, Rugged Appeal
Dr. Squatch takes a different approach, focusing on bold, masculine scents and fun, rugged branding. While some of their bars use plant oils, not all are true castile soaps. Dr. Squatch is great for those who want a strong scent and a “manly” shower experience, but some bars can be more exfoliating or harsh for sensitive skin.
Prep U: Castile Soap Designed for Teens & Sensitive Skin
Prep U’s Sandalwood Castile Soap Bar is crafted specifically for teens and young adults—especially those with sensitive, acne-prone, or developing skin. Our cold-processed formula uses a blend of coconut, olive, castor, and shea butter oils, combined with soothing sandalwood, amyris, and vetiver essential oils. The result is a gentle, hydrating bar that cleanses without stripping or irritating your skin.
Unlike other brands, Prep U is all about empowering teens with safe, effective products and educational resources for building healthy routines. We’re parent-founded, third-party verified, and committed to ingredient transparency.
Why Choose Prep U’s Sandalwood Castile Soap Bar?
When it comes to natural skincare for teens, Prep U’s Sandalwood Castile Soap Bar stands out for its thoughtful formulation and skin benefits. Here’s why:
Our Sandalwood Castile Bar is cold-pressed in small batches, preserving the rich, moisturizing power of coconut, olive, castor, and shea butter oils. The addition of sandalwood, amyris, and vetiver essential oils creates a calming, woody aroma that soothes both skin and senses. This bar is designed to deeply hydrate, revitalize, and protect your skin’s natural moisture barrier—making it ideal for dry, sensitive, normal, combination, and even aging skin.
We never use aluminum, parabens, phthalates, sulfates, gluten, or animal byproducts. Every ingredient serves a purpose: to cleanse, calm, and care for your skin.
Plus, our commitment goes beyond the bar. Prep U offers grooming guides, educational content, and a rewards program to support teens and their families in building healthy, confident routines.
Featured Benefits of Prep U’s Sandalwood Castile Soap Bar
- Deep Hydration: Shea butter and coconut oil nourish and lock in moisture.
- Gentle Cleansing: Perfect for sensitive, acne-prone, or developing skin—no harsh chemicals, ever.
- Calming Scent: Sandalwood, amyris, and vetiver essential oils provide a subtle, refreshing aroma.
- Clean & Conscious: Vegan, cruelty-free, third-party verified, and eco-friendly.
- Parent-Approved: Founded by a mom, trusted by parents, and loved by teens.
The Bottom Line
Castile soap is more than a trend—it’s a return to simple, plant-based skincare that’s safe for you and the planet. Whether you’re comparing Dr. Bronner’s, Dr. Squatch, or seeking something tailored for teens, Prep U’s Sandalwood Castile Soap Bar delivers the gentle, effective clean your skin deserves.
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