How Essential Oils Could Save Ancient Monuments

Ancient stone doesn’t crumble only because of time. In many places, it’s being quietly eaten alive by fungi—organisms so small you never see them, yet strong enough to crack marble and darken monuments that have stood for thousands of years.

From Roman columns in Turkey to temples, statues, and tombs across Africa, Asia, and Latin America, microscopic fungi are accelerating the loss of cultural heritage. And the tools we’ve long used to fight them—harsh chemical biocides—often damage the stone, poison nearby ecosystems, or become too expensive to sustain. But here’s where it gets interesting: a new study suggests that the solution may smell more like a kitchen than a chemistry lab.

The Problem, Explained Like Cooking

Think of stone like a loaf of bread left out in humid air. Over time, mold creeps in, sends roots deep into the structure, and weakens it from within. On monuments, this “mold” is often a group called black microcolonial fungi. They wedge themselves into tiny cracks, secrete acids, and slowly pry stone apart—grain by grain.

Conservators have traditionally responded with strong synthetic chemicals, similar to bleaching moldy bread. Effective at first, yes—but repeated use damages the surface, harms workers, and disrupts surrounding soils and microbes. In hot, humid, or resource-limited settings, these tradeoffs are especially costly.

So researchers asked a deceptively simple question: What if plants already evolved a safer antifungal defense?

An Unexpected Ally: Aromatic Herbs

A research team working in the Ancient City of Side in southern Türkiye turned to plants from the Lamiaceae family—the same group that gives us oregano, marjoram, and mint. These plants have been used for centuries in cooking and medicine, especially across the Mediterranean, the Middle East, and parts of Africa.

The scientists extracted essential oils from three species:

• Marjoram
• Wild oregano
• Wild mint

They then tested these oils against fungi isolated directly from infected stone monuments. Instead of guessing in the lab, they brought the real culprits—the same fungi attacking statues and columns—into controlled experiments.

But here’s the twist: they didn’t just ask whether the oils worked. They tested how much was needed by comparing very low doses to higher ones. And the difference mattered a lot.

The “Aha” Moment

At low concentrations, the oils slowed fungal growth. At higher concentrations—around 3%—fungal cell counts dropped dramatically. In some cases, spore numbers were cut by more than half.

Why? Essential oils don’t act like blunt chemical hammers. They behave more like soap on greasy hands. The oils dissolve fungal cell membranes, interfere with enzymes, and disrupt the fungus’s ability to eat and reproduce. Thin-walled fungi collapsed fastest. Thicker-walled species resisted more—but still lost ground.

One oregano species stood out as especially powerful, outperforming the others across multiple fungal types. But here’s the key insight: dose mattered more than plant choice. Too weak, and the fungi survived. Strong enough, and growth stalled.

Why This Matters Beyond Ancient Ruins

This research isn’t just about saving statues. It’s about how we protect valuable things in a warming, wetter world.

Many low- and middle-income countries are home to priceless heritage sites but lack access to expensive conservation chemicals or specialized equipment. Essential oils are:

• Plant-based
• Biodegradable
• Locally producible in many regions
• Safer for workers and visitors

Imagine a restoration team near a historic mosque, church, or temple using locally sourced plant oils instead of imported chemicals. Or a small museum protecting stone artifacts without risking chemical runoff into nearby water sources.

This approach also fits a broader shift in science: moving from “maximum force” solutions to targeted, sustainable interventions.

Not a Silver Bullet—And That’s Okay

The researchers are careful not to oversell the results. Essential oils didn’t completely wipe out fungi. Some species recovered over time. Oils can also change chemically as they age, potentially affecting stone color or texture if misused.

In other words: this isn’t magic. It’s a tool.

But tools matter. Especially ones that are affordable, adaptable, and rooted in natural chemistry that humans already understand and trust.

And here’s the deeper lesson: conservation doesn’t always need newer technology. Sometimes it needs better listening—to plants, to materials, and to context.

From Myth to Method

For centuries, aromatic plants have been used as folk remedies. Then modern science dismissed them as unscientific. Now, through careful experimentation and statistical rigor, researchers are rediscovering that some traditional knowledge has had real biochemical foundations all along.

We thought only synthetic chemicals could protect the stone. But the data shows that nature has already engineered alternatives.

Let’s Explore Together

• Could plant-based preservation methods work for monuments in your region?
• If you were on this research team, what would you test next—different plants, climates, or materials?
• What everyday problem around you might have a low-cost, nature-based solution waiting to be studied?

Science doesn’t always shout. Sometimes it smells like oregano—and quietly changes how we protect the past.