Mucous Membrane
Definition
The thin, moist tissue that lines body openings, including the inside of the lips and mouth. Lip skin sits at the transition zone between external skin and internal mucous membrane, which is why it is thinner, more absorbent, and more sensitive than regular skin. This is also why the ingredients in lip balm matter — they are absorbed more readily than products applied elsewhere on the body.
Related Terms
Lip Barrier
The protective outermost layer of lip skin that prevents moisture loss and protects against environmental damage. Unlike regular skin, the lip barrier is much thinner and lacks oil glands, making it more vulnerable to drying and damage. Lip balm ingredients like beeswax supplement and strengthen this barrier, while oils like coconut and jojoba support its natural function.
Vermilion Border
The sharp line between the colored part of your lips (vermilion) and the surrounding skin. The vermilion border is one of the most distinctive features of the human face and is particularly sensitive to dryness and damage. Lip balm should be applied to cover the entire vermilion area including the border for complete protection.
Hypoallergenic
A term describing products formulated to minimize the risk of allergic reactions. While not a regulated term by the FDA, truly hypoallergenic products use few, well-tolerated ingredients. Numbrrrz's 4-ingredient formula with no fragrances (in the Unscented variety), preservatives, or common allergens makes it one of the most hypoallergenic lip balms available.