Eddy Current: Circular flow patterns in fluids around hair

ByDr. Celestine (Certified Trichologist)

What is Eddy Current?

Eddy current is a type of electrical current that swirls inside a conductor when it is exposed to a changing magnetic field. Think of it like tiny, invisible whirlpools of electricity forming inside your hair when you use certain heated tools. Most people miss this: these currents generate heat directly within the hair shaft itself, not just on the surface.

How Eddy Current Heats Your Hair

Your hair contains tiny amounts of minerals and water that can conduct electricity. When a tool with a rapidly changing magnetic field gets close, it induces these swirling currents inside the strand. The electrical resistance inside your hair then converts that current’s energy into heat.

Think of rubbing your hands together very fast to create warmth. The eddy current does something similar, but the friction is happening on a microscopic level inside the hair. I see this internal heating pattern clearly under the microscope in clients who frequently use such tools.

The Eddy Current Damage Surprise

Because the heat is generated from within, it can cause hidden damage to the hair’s inner core, or cortex, before the surface even feels overly hot. This is a common reason clients come to me with breakage they can’t explain.

They often assume the tool is safe because it doesn’t scorch their hair. The reality is the damage is happening from the inside out. I always advise pairing these tools with a truly effective heat protectant that can help mitigate this internal thermal shock.

Eddy Current vs. Traditional Heat Tools

Traditional tools like flat irons work by conducting heat from a hot plate directly to the hair’s outer surface. The heat then slowly transfers inward. Eddy current tools are different because they make the hair heat itself up from the inside.

This can lead to a more even distribution of heat in some cases. However, it also makes it dangerously easy to overheat the delicate proteins living inside the cortex. I recommend using the lowest effective setting to minimize this risk.

Will It Work For You?

✓ Yes

  • If your hair is in good condition with no existing protein damage.
  • When you need a quick, smooth style and can use a low heat setting.
  • If you consistently use a high-quality heat protectant spray or cream.

✗ No

  • If your hair is already chemically processed, bleached, or has high porosity.
  • When you are experiencing active breakage or significant split ends.
  • If you have a sensitive scalp or conditions like scalp psoriasis, as the magnetic fields may cause irritation.

From My Experience

In my clinic, I use a specialized microscope that can show the subtle bubbles forming inside the cortex from eddy current overheating. This is different from the classic bubble hair caused by traditional open-flame heat.

This internal damage is why a simple surface-level conditioning mask often isn’t enough for repair. The hair needs small protein molecules that can penetrate and fill those microscopic voids created by the internal steam. Look for products with hydrolyzed proteins.

My biggest tip is to listen to your hair. If it feels gummy when wet or stretches too far before snapping, it’s signaling internal protein loss. This is a clear sign to avoid all heat styling, especially tools that utilize eddy current technology, until the hair has recovered.

Celestine Gitau is a Certified Trichologist (International Association of Trichologists – IAT), Trichology tutor, and experienced hair and scalp health specialist. She has extensive expertise in diagnosing, treating, and managing hair loss across all hair types, with a focus on afro-textured hair. Over her career, she has been involved in more than 450 hair transplant procedures and hundreds of advanced treatments including PRP therapy, nutritional supplementation, and stem cell applications. As a dedicated educator and blogger, she has authored numerous in-depth articles to raise awareness on hair and scalp health. Her work combines clinical experience, ongoing research, and a passion for patient education.
Note: The information shared is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for personalized guidance.