Introduction
Aside from the colloquialism that someone has ‘thick’ or ‘thin’ skin, most of us never think about the thickness of skin. It varies substantially across the body, and it’s not surprising. For instance, the palms of your hands and soles of your feet are thicker than your forearms and calves. This makes sense, due to the relative amount of wear and tear that each undergoes each day.
Your lips have particularly thin and sensitive skin. This makes sense as they function as the gateway to your mouth and are designed to warn you when something isn’t good to ingest.
Evolutionary Explanation
Sensory Perception: Lips are involved in several critical functions, such as eating, speaking, and kissing. They help guide food to the mouth, complementing the role of taste buds. Their sensitivity aids in detecting the texture and temperature of food. The sensitivity of lips plays a role in nuanced facial expressions and speech.
Evolutionary Function: As the first entry point for food, lips’ sensitivity helps detect the safety and temperature of food. They also play a role in social bonding and our connection to others, like kissing, lip reading, and nurturing.
Physiological Explanation
The skin on the lips is significantly more sensitive than the skin on most other parts of the body. Here’s why:
Thinner Skin: The skin on the lips is much thinner than the skin on the rest of the body. While most of the body’s skin has up to 16 layers (including a thicker outer layer called the stratum corneum), the lips have only 3-5 cell layers. Furthermore, this thin layer lacks the protective keratinized outer layer found in most skin, making the lips more exposed and sensitive to external stimuli. This makes them more delicate and vulnerable to environmental factors.
Lack of Melanin: Lips have less melanin, the pigment that protects skin from UV rays. This makes the lips more susceptible to sun damage, which can lead to burning and chapping more easily than other areas of the skin.
Fewer Protective Oils: Unlike the rest of the skin, the lips do not have sebaceous (oil) glands, which produce the natural oils that help keep the skin moisturized and protected. Without these oils, the lips are more prone to drying out and becoming chapped.
High Concentration of Nerve Endings: The lips are densely packed with nerve endings, which are part of the somatosensory system. These nerve endings allow the lips to detect even subtle stimuli such as temperature, touch, pain, texture, and pressure, hence why even slight irritations or environmental changes can cause discomfort on the lips.
Greater Exposure: The lips are almost always exposed to the environment, unlike much of the skin, which is often covered by clothing. This constant exposure to elements like wind, sun, and cold air further increases their vulnerability.
Rich Blood Supply: Lips are highly vascularized, meaning they have a rich supply of blood vessels just beneath the surface. This contributes to their redness and sensitivity, as the blood vessels are closer to the surface than in other parts of the skin. It also means that anything you put on your lips is more readily absorbed into the bloodstream, so reconsider the quality of your lip balm.
Lack of Protective Structures: Lips do not have hair follicles or sweat glands, which provide additional protection and insulation in other parts of the skin.
How to Treat Lips
Because of these factors, the lips require special care to keep them healthy and protected, especially when they’re exposed to harsh climates and extended sunlight. This includes regular moisturizing, sun protection, and avoiding irritants that can cause damage.
Since the blood vessels are so close to the surface, remember that anything you place on your lips, such as lipstick and lip balm is more readily absorbed into your bloodstream. Make sure that you use high-quality, organic, and fragrance-free lip products. Try to find ones without preservatives and only natural ingredients you recognize, such as beeswax, shea butter, essential oils, arrowroot powder, and the like.
