The Life-Saving Glass Test That Can Help You Recognize A Serious Medical Emergency

When your child is sick, you can feel somewhat helpless, especially when they are just babies. They can't tell you what's wrong, so it can be hard to know if they need to be taken to the doctor or just need a little TLC. This is especially true when you're dealing with a rash.

A rash is an inflamed, bumpy area of skin, per Cleveland Clinic. It can be a reaction to an irritant, like laundry detergent, or it can be a symptom of something more serious, like bacterial meningitis or septicemia. Some viruses like chickenpox; COVID-19; and hand, foot, and mouth disease can also come with a rash. Knowing whether the rash is due to a skin irritant or something more sinister typically takes some sleuthing. In addition to looking at additional symptoms like a fever, you can do a blanch test with a glass to help discern whether you might need to see a doctor.

To ensure you stay in the know, we'll show you how to perform a glass test and dissect the results. We'll also go over other symptoms to watch out for when it comes to life-threatening conditions like bacterial meningitis and septicemia.

Specific rashes can require medical attention; and some Tiktokers, like @drabby6, are pointing out the benefits of using the blanching test with a glass to know when a rash could be serious. According to Dr. Dawn Davis, professor of dermatology and pediatrics at the Mayo Clinic, "Blanching of the skin is when the skin loses color from blood being displaced away from where pressure is applied" (via Today). Typically, a healthcare professional presses a glass slide onto the rash to see if it changes (turns white) or stays the same (per Healthline).

You don't need a doctor to perform a blanch test, however. Grab a glass out of your cupboard or dishwasher to do this test at home. Meningitis Now suggests pressing the side of the glass firmly against the skin where the rash is. Watch to see how it reacts. Blanching rashes will discolor, like turning white, when pressure is applied to the area. Non-blanching skin will maintain its color. Dr. Adam Friedman, professor and chair of dermatology, told Today, "Just be careful when applying pressure because you don't want to break the glass on the skin."

The reason for the test is the vessels underneath the skin. When a rash is blanchable, it means that the color leaves the blood vessels when pressed. Those that do not blanche have blood that has leaked outside of the vessels.

A rash not blanching is a sign of concern, according to Today. For example, it can be a symptom of meningitis or septicemia. When these conditions are at play, you'll have no blanching along with other symptoms like high fever. 

Meningitis can be a life-threatening illness that causes swelling of the meninges, while septicemia is blood poisoning, explains the Meningitis Research Foundation. These infections can be caused by the same bacteria, like Streptococcus pneumoniae. In addition to a skin rash, sufferers of bacterial meningitis have a high fever, stiff neck, headache, sleepiness, and lack of appetite, according to the Mayo Clinic. Newborns and babies might also exhibit constant crying, trouble waking, poor feeding, and vomiting. Septicemia exhibits many of the same symptoms beyond the stiff neck (per Penn Medicine).

The reason these conditions present with a rash is they are "a systemic infection that's manifesting in the skin because of the dissemination of that bacteria through the blood," according to Dr. Friedman. The bacteria damages the vessels causing bleeding into the skin. These conditions require immediate medical attention in a hospital facility so antibiotics and fluids can be administered.