1. Nervous Hands Can Feel Both Cold and Wet
When your turn to speak is coming up, your heart races and your mouth dries out. Many people have had a friend say, "Your hands are cold," when they shook hands during this moment. The strange part is that the same palm is damp at that time. You are not sweating because it is hot. Your hands are cold, but they are also damp.
These two things are thought to happen through different systems in the body. Both are explained as preparations for a situation where you need to act quickly. Let us look at why your hands get cold first. What is happening inside your blood vessels?
Safety Note: If your hands stay cold for a long time, it might be a different issue. In that case, please talk to an adult or a doctor.
2. The Sympathetic Nervous System Narrows Skin Blood Vessels
Inside your body, there is a system called the sympathetic nervous system. It works when you need to react to stress. According to an encyclopedia entry, when this system works, almost all blood vessels shrink, and blood pressure rises. A substance called adrenaline is also released more easily from the adrenal glands [4].
The skin on your palms and fingertips receives this signal. A review of skin blood flow says that hairless skin on hands and feet has many nerve fibers that control the opening and closing of blood vessels [1]. The same review notes that mental upset can also cause some blood vessels to close [1].
When blood vessels shrink, less blood flows through them. Warm blood has trouble reaching your fingertips, so the skin temperature drops, and your hands feel cold. This means that your heart pounding and your cold hands are both part of the same "get ready" signal. But how much does the temperature actually drop?
3. Experiments Show Fingertip and Nose Temperatures Drop
Researchers have studied how much the temperature changes. A review of experiments that caused fear reported that fingertip temperature dropped by a maximum of about 2°C. This was thought to be caused by the shrinking of blood vessels [2]. However, "about 2°C" was the largest drop in those specific experiments. It does not mean everyone’s temperature drops by 2°C.
Another experiment was announced by the University of Sussex in the UK. In this study, 29 people helped by preparing for a speech while listening to white noise. While they were stressed, the temperature of their noses dropped by 3–6°C. When the stress ended, the temperature returned to normal in a few minutes [3]. Since these numbers come from a university news article, it is best to understand them as results from "this experiment."
Both the nose and the fingertips are far from the center of the body. This raises a question: Do blood vessels in distant parts of the body shrink first? Next, let us look at the structure of the blood vessels in the fingertips.
4. Blood Shortcuts in Fingertips (AVAs) Close When You Are Nervous
The blood vessels in your fingertips have a special structure. Hairless skin has many "shortcuts" called arteriovenous anastomoses (AVA), which connect small arteries directly to small veins. The sympathetic nervous system controls whether these shortcuts are open or closed [1].
Numbers are given for how many of these shortcuts exist. Under the fingernails, there are about 600 per square centimeter (100 square millimeters). In the fleshy part at the base of the thumb and the little finger, there are about 100 per square centimeter [1]. This means there are about 6 per square millimeter under the nails and about 1 per square millimeter in the fleshy parts. Note that the density is not the same across the whole palm.
When the sympathetic nervous system is activated, these shortcuts can close, and less blood flows to the fingertips. While skin blood vessels shrink, the blood vessels in your skeletal muscles widen. Blood is moved toward the muscles instead [5]. This is considered part of preparing the body to run or escape.
It is not clear from these materials if cold fingertips are special to hands and feet. Next, we look at the sweat on your palms, which happens opposite to the coldness.
Safety Note: It is safe to understand that fingertips are one of the places where blood vessels shrink easily.
5. Does Palm Sweat Help You Grip Things?
Sweat on the palms is different from sweat caused by heat. There are two types of sweating. One is thermal sweating, which happens all over the body when body temperature rises. The other is emotional sweating, which happens on the palms, soles of the feet, and armpits due to mental tension. Emotional sweating can happen even when the temperature is comfortable [6].
Why do palms sweat? One explanation is that sweat acts as a non-slip surface. A study from 1975 looked at rats and dogs that have sweat glands on their paws. When these animals ran, sweat appeared on their paws. The researchers found that if they used medicine to stop the sweat, the coefficient of static friction between the paw and floor dropped significantly [7].
This result supports the idea that sweat might help prevent slipping on the soles of feet. It is similar to the idea that slightly damp palms might make it easier to grip when climbing. However, this was an experiment with animals. It has not been confirmed that the same effect happens on human palms.
With this in mind, cold fingertips and wet palms do not seem to contradict each other. The preparation to restrict blood flow and the preparation to grip and stand firm are happening in the same hand at the same time.
6. How to Observe Your Own Fingertips and Palms When Nervous
You can observe this using things you have at home. Before a moment when you feel nervous, like a presentation or a game, touch your fingertips to your own cheek. Notice if they feel cold, and write it down later. Also check if your palms are wet.
Then, wait a few minutes after the event is over. Touch your fingertips to your cheek again. If your fingertips feel less cold again, it is consistent with the report from the University of Sussex experiment where nose temperature returned in a few minutes [3]. If it does not return, there might be reasons other than nervousness.
However, everyone is different. The goal of this observation is not to decide who is "normal" compared to friends. If your hands stay cold for a long time, please tell a family member or a doctor.
To make it easier to compare later, write down the "coldness" and "wetness" on a scale of three: strong, medium, or weak. If you line them up by situation, you might see patterns in how your hands react.