Gentian violet - a compound that is both a dye and a medicine

One early September morning in 1977, I hustled up three flights of stairs to the third floor of College Hall at Washington State University in Pullman, for my first pharmacy laboratory session. I carried my brand-new white lab coat, which was mandatory attire for this and all future lab sessions. In my other hand was a pack of tissues because I was allergic to ragweed, which was blooming that week.

My assignment that day was to make a bottle of Gentian Violet 1% solution. The procedure was to precisely measure the required amount of powdered gentian violet, then add it to alcohol and purified water. Just 3 ingredients. What could go wrong?

Cautiously tapping the iridescent green crystals onto a pale green rectangle of waxed paper, I carefully weighed the pile, making sure I had 100mg. Picking it up, I cradled my precious powder. Returning to my lab station, I avoided bumping into anything or anyone. But as I set the crystals down on the black countertop, disaster struck: I had to sneeze.

I quickly turned my head, somehow avoiding spraying powdered dye across my lab bench. In relief, I promptly added the colored powder to my alcohol and water mixture before another sneeze could strike.

The rest of the morning went smoothly, but that sudden sneeze would haunt me for years. Pulling my lab coat out of the washing machine the following week, I stared in dismay. My pristine white coat was accented with bright purple speckles running across and down its front. Despite repeated bleaching, they refused to fade. I wasn’t the only one with colored speckles on my lab coat, but mine was the most spectacularly purple-speckled lab coat for the entire rest of that year and the next.

Gentian violet is a compound that is both a dye and a medicine. Discovered in 1861, Hans Gram would report 13 years later that gentian violet could irreversibly color certain bacteria. This proved instrumental in classifying bacteria and became the basis for the Gram stain method of identifying bacteria still widely used today.

Gentian violet (AKA crystal violet) is used in laboratories across the globe to help identify bacteria. However, it’s also an effective antibacterial and antifungal agent. Gentian violet can treat infections caused by gram-positive bacteria, which live on the skin, and yeast infections of the mouth, skin, and vaginal tract.

Although mostly replaced by newer antibiotics and antifungal agents, gentian violet is still used in veterinary medicine and in developing countries. With resistance growing to our current antibiotics, gentian violet is getting a second look; not only is it practical, but it's also inexpensive, simple to use, with very few side effects.

Thrush in infants is usually treated with a suspension of nystatin painted on the inside of each cheek 3-4 times daily for a week. At the same time, it takes only one application of Gentian Violet 1%, the exact same product I made over 40 years ago in the pharmaceutics lab, to treat thrush.

The main disadvantage to using gentian violet is the one I had personal experience with: it stains clothing. Although gentian violet will stain clothing forever, treated skin or mucous membranes only stay bright purple for about 2 weeks before fading.

Fluorescein is a dye used in diagnosing eye injuries and damage to your cornea. Small paper strips are soaked in a fluorescein solution, dried, sterilized, and sealed into individual packets. When the sterile fluorescein strip touches your eyeball, it mixes with tear fluid to create a fluorescein solution that coats your eye.

Healthy, intact corneal tissue won't pick up any fluorescein. In contrast, worn spots or abrasions from contact lenses appear as bright green areas. Foreign bodies show up surrounded by a fluorescent green ring. The mild anti-infective action of fluorescein is also beneficial because injured eyes are very susceptible to infection.

Phenazopyridine is a reddish-orange dye. Sold as a prescription medicine under the brand name of Pyridium® in 100mg and 200mg coated tablets, phenazopyridine is also available without a prescription at a lower strength of 95mg in the products Azo®, Uristat®, and in generic “Urinary Pain Relief."

Originally used to treat bladder infections, phenazopyridine isn’t very effective against bacteria. Instead, it can relieve urinary urgency, pain, and burning often experienced from a bladder infection, often within 15 minutes. Today, phenazopyridine is prescribed along with an antibiotic to relieve urinary urgency and burning of bladder infections.

When using it, remember that phenazopyridine is a dye. It turns urine deep reddish-orange and stains clothing.

Dr. Louise Achey, Doctor of Pharmacy, is a 43-year veteran of pharmacology and author of Why Dogs Can’t Eat Chocolate: How Medicines Work and How YOU Can Take Them Safely. Get clear answers to your medication questions at her website and blog, TheMedicationInsider.com. Ó2023 Louise Achey