Highlighters are writing instruments that mark text with translucent, brightly colored ink, using fluorescence to make words stand out. Although commonly used in academic and office settings, their vibrant colors often raise concerns about potential toxicity. Modern, brand-name highlighters generally pose a low-toxicity hazard when used as intended. The risk to human health is minimal, even in cases of minor, accidental exposure, due to the specific chemical composition and the small volume of ink.
Key Components and Potential Hazards
The vibrant, glowing appearance of a highlighter comes from a carefully formulated ink, which is primarily a mixture of solvents and fluorescent dyes. The fluorescent pigments, such as pyranine for yellow or rhodamine compounds for pink, absorb ultraviolet light and re-emit it as the intense visible light that creates the distinct glow. These dyes make up a very small percentage of the total ink composition, often less than five percent.
The majority of the ink is a solvent, which is the liquid base that suspends the dye and allows it to flow onto the paper. Most highlighters use a water-based formula, which is considered the lowest risk option, often containing water and glycol solvents. Other formulas are solvent-based, sometimes incorporating alcohol or glycol ethers to promote faster drying and smear resistance. Alcohol-based formulas do present a slightly higher, though still low, risk upon ingestion due to the presence of the alcohol solvent.
The components are used in concentrations and forms that are not typically harmful in small quantities. For instance, glycol solvents, similar to those used in many cosmetics, are present in amounts that do not pose a significant health threat. The primary concern with the chemical composition is the potential for irritation to sensitive tissues, such as the eyes or stomach lining, rather than systemic poisoning.
Understanding the “Non-Toxic” Label
Many highlighters carry a “Non-Toxic” designation, which is an important indicator of consumer safety but is often misunderstood. This label does not mean the product is safe to eat or drink, but rather that it is safe for typical use and minor, accidental misuse, such as getting a small amount of ink on the skin. The designation typically signifies compliance with safety standards, such as ASTM D-4236, which is the standard practice for labeling art materials for chronic health hazards.
The Art & Creative Materials Institute (ACMI) plays a large role in this certification process, and products often display their Approved Product (AP) seal. This seal confirms that a medical expert has toxicologically evaluated the product. It certifies that the product contains no materials in sufficient quantities to be toxic or injurious to humans, covering both acute and chronic health concerns. Products bearing the AP seal are deemed safe for use by all ages, including children.
Even with the non-toxic certification, the limits of the safety standard must be understood. The assessment is based on the product’s intended use and the likelihood of accidental exposure, such as a child tasting the marker tip. The safety evaluation ensures the product is formulated to minimize the risk of injury or long-term health problems from this type of exposure.
Exposure Scenarios and Emergency Action
Accidental exposure to highlighter ink commonly occurs through ingestion, skin contact, or eye contact; the appropriate response depends on the route and severity of the exposure. Ingestion is the highest concern for parents, but the ink is considered minimally toxic, and serious poisoning is extremely rare due to the small quantity of ink. Swallowing a small amount may cause mild mouth irritation, temporary staining of the tongue, nausea, or a minor upset stomach.
If ink has been swallowed, rinse the mouth thoroughly with water, then drink a small amount of water or milk to dilute the ink and reduce stomach irritation. It is advisable to call a poison control center for expert guidance, as they can assess the risk based on the specific product and the amount ingested. If the person experiences severe symptoms such as difficulty breathing, seizures, or collapse, call emergency services immediately.
Skin contact is common during regular use and may cause temporary staining or mild irritation in sensitive individuals. Wash the affected area immediately with soap and water until the color is removed. Eye contact is more irritating; if ink splashes into the eye, flush it immediately with a gentle stream of cool water for at least 15 minutes. If eye irritation, pain, or blurred vision persists after flushing, medical attention or a call to the poison control center is warranted.