MMA monomer (methyl methacrylate) is genuinely harmful. The FDA concluded in the 1970s that liquid methyl methacrylate is a “poisonous and deleterious substance” that should not be used in nail preparations, and the agency took court action to remove products containing 100 percent MMA liquid from the market. Despite this, some nail salons still use it because it’s significantly cheaper than safer alternatives.
Why MMA Was Banned for Nail Use
In the early 1970s, the FDA received numerous complaints of personal injury from fingernail extenders containing MMA monomer. After investigating the injuries and consulting dermatologists, the agency pursued seizure actions, voluntary recalls, and a preliminary injunction against at least one manufacturer. By 1974, MMA was effectively banned from all nail products because it caused deterioration of nail plates, nail dislocation, and allergic dermatitis in both clients and technicians.
The safer replacement used in legitimate acrylic nail products is ethyl methacrylate (EMA). It’s a closely related chemical but produces a more flexible, less rigid enhancement that bonds to the nail without the same level of risk. Most professional-grade acrylic liquids sold today are EMA-based.
What MMA Does to Your Nails and Skin
MMA causes problems that EMA simply doesn’t, and the damage can be permanent. The most well-documented effects on clients include severe contact dermatitis (red, itchy, blistered skin around the nail), paronychia (painful infection of the skin folds beside the nail), and nail dystrophy, which means the nail plate itself becomes misshapen or destroyed. In some cases, these nail changes are permanent.
One particularly concerning effect is paresthesia: numbness, tingling, or loss of sensation in the fingertips. This happens because MMA can damage the nail bed and surrounding tissue so severely that nerve function is affected. Published case reports describe these sensory changes persisting long after the acrylic is removed.
MMA also bonds to the natural nail with extreme rigidity. Where an EMA-based acrylic has some flex and will give way under pressure, MMA-hardened acrylic is so rigid that a sudden impact, like catching your nail on something, can tear the natural nail plate off the nail bed rather than simply popping the enhancement loose. This makes traumatic injuries far more likely and far more severe.
Risks for Nail Technicians
If MMA is bad for clients who sit in a chair for an hour, it’s considerably worse for technicians who breathe its vapors all day. The EPA has documented both short-term and long-term respiratory effects from inhaling methyl methacrylate, including nasal symptoms and reduced lung function in chronically exposed workers. Neurological symptoms, such as headaches, dizziness, and cognitive changes, have also been reported after acute exposure.
At high exposure levels, the risks escalate further. One study found an association between occupational MMA exposure and cardiovascular disorders. Animal studies using chronic high-level inhalation showed degenerative changes in the liver, kidney, brain, spleen, and bone marrow, along with significant weight loss and lethargy. While salon exposure levels are lower than controlled laboratory settings, technicians performing multiple acrylic sets per day in poorly ventilated rooms face cumulative risk that builds over months and years.
Why Some Salons Still Use It
The short answer is cost. MMA liquid monomer is dramatically cheaper than EMA-based products, which is why it tends to show up in discount salons offering full acrylic sets at unusually low prices. The FDA’s original enforcement actions targeted manufacturers, not individual salons, which creates a regulatory gap. While many states have passed their own laws banning MMA in salon settings, enforcement is inconsistent, and the product remains available through unregulated supply channels.
How to Tell If a Salon Uses MMA
You can’t always tell by looking at the bottle, since some products are mislabeled or decanted into unmarked containers. But there are three reliable warning signs to watch for during and after your appointment:
- Unusually strong or harsh odor. MMA has a distinctive, acrid chemical smell that’s noticeably different from the milder scent of standard acrylic liquids. If the fumes feel overwhelming or unfamiliar, that’s a red flag.
- Extreme hardness after curing. MMA-based acrylics set into an unusually hard, dense material that’s very difficult to file down, even with coarse abrasive grits. If your technician seems to be working much harder than expected to shape the enhancement, the product may be MMA.
- Won’t dissolve in acetone. Standard EMA acrylics will soften and break down when soaked in acetone-based remover. MMA acrylics resist solvents almost entirely, meaning removal requires aggressive filing or prying, which causes additional damage to the natural nail.
The most straightforward approach is to ask your technician directly what monomer they use and to check the product label. A reputable salon will have no problem showing you the bottle. If the label doesn’t list ingredients, or if the technician is evasive, consider going elsewhere.
MMA in Other Industries
It’s worth noting that methyl methacrylate isn’t banned from existence. It’s widely used in industrial applications, including bone cement for orthopedic surgery, dental fillings, and Plexiglas manufacturing. In those contexts, it’s used under controlled conditions with proper ventilation, protective equipment, and formulations designed to minimize skin contact. The concern specific to nail salons is that liquid MMA monomer contacts skin directly, bonds to living tissue, and exposes both client and technician to prolonged vapor inhalation in spaces that often lack adequate ventilation.