Coolant Risks: Contact Dermatitis

Coolant is essential to CNC machining, but if mismanaged, it can quietly damage what matters most: your people.

Contact dermatitis is one of the most common occupational health risks in machine shops. It’s a form of skin inflammation caused by irritants or allergens, and in this environment, the leading cause is direct contact with metalworking fluids (MWFs), commonly referred to as coolant.

A NIOSH Health Hazard Evaluation at a U.S. engine machining plant found that 75% of employees with visible rashes had skin symptoms likely caused by coolant exposure (NIOSH Report No. 2015-0070-3304, p. ii). These weren’t isolated incidents. Over 75% of machinists in key departments reported skin contact with coolant at least once a week. Combine that with poor concentration control and manual handling, and you’ve got a perfect storm for skin damage.

Coolant isn’t just water and oil. It contains biocides, rust inhibitors, and emulsifiers, and when not maintained properly, it becomes a breeding ground for bacteria, fungus, and chemical imbalance. NIOSH reports that these factors directly contribute to skin issues, including irritant contact dermatitis, allergic dermatitis, and oil folliculitis. Left untreated, symptoms can persist and become chronic, such as cracking, itching, thickened skin, and persistent discomfort.

Manual refills are a big part of the problem. Shops relying on buckets or pre-mix venturi systems put machinists in direct contact with the fluid, often without consistent PPE enforcement. The report observed coolant spraying, spills, and skin contact, even during routine tasks, despite posted personal protective equipment (PPE) requirements.

So what’s the fix?

FlexxCool automates coolant top-up and concentration management. By eliminating manual mixing and maintaining stable fluid conditions, it drastically reduces the root causes of dermatitis. FlexxCool systems keep coolant oxygenated, flowing, and accurately balanced, eliminating stagnant zones and bacterial buildup.

In fact, maintaining full sumps and the correct concentration eliminates 80% of coolant issues, including skin irritation. That’s not just an operational improvement, it’s a health and safety upgrade.

To reduce dermatitis risk in your shop:

• Eliminate manual coolant top-up wherever possible.
• Use automated systems to maintain consistent coolant concentration.
• Enforce proper PPE for anyone handling coolant.
• Train employees on risks and early symptoms of exposure.
• Keep coolant moving and oxygenated to avoid bacterial growth.

According to NIOSH, contact dermatitis accounts for up to 95% of all occupational skin disease. With rising awareness of occupational health risks, shops can’t afford to ignore the damage caused by poor coolant practices. Contact dermatitis is preventable. It’s a solvable problem, and it starts with how you handle your coolant.

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