皮膚上的「墨」或者「痣」的學術名稱叫做黑色素細胞痣 (melanocytic naevus)。佢哋其實係一堆黑色素細胞(melanocytes)的凝聚及增生。這些黑色素細胞並不一定是黑色的所以有些墨痣是深色的，有些墨痣是淺色的。有些墨痣是平的，有些墨痣是凸出來的。
佢哋可以出現在身體任何一個地方，包括黏膜位置（即係咀唇，性器官，肛門等等）。
「墨」同埋「痣」其實冇分別。有些人夾硬將佢哋分類成唔同嘅皮膚情況，引人注目，加強點擊率。墨係廣東人嘅用語。係口語，寫唔出來的。勉強要寫就會寫個「墨」字。有時候廣東人會加個「疒」字部首，變成「癦」字。看上去就好似比較正式。「痣」就係內地，台灣，以及其他東南亞國家例如星加坡等地所採用的命名。而「痣」一字亦都係正式的醫學名詞。所有中文醫學文章，文獻或教科書都會用上「痣」這一個字。並沒有「墨」這個字出現。
墨/痣的形成，有分天生，以及後天形成。天生的黑色素痣大概有1%。其他絕大部份情況都係兩歲之後出現。有些人青春期發育的時候墨痣的數量會急速增加。有很多墨/痣的人士，通常都同遺傳有關係。後天的墨痣，也可能會受到紫外光影響而增大。其他原因，例如懷孕期間，因為荷爾蒙影響，墨/痣都可能會顏色變深。
總結：墨痣並非表面那麼簡單，其根部深淺千變萬化，唯有受過皮膚學訓練的醫生才能準確識別，避免誤判導致疤痕或復發。非醫護很可能缺乏這類判斷力。
The medical term for mole on the skin is melanocytic naevus. So mole and naevus are the same thing. They are essentially clusters and overgrowths of melanocytes—the cells responsible for producing pigment on skin. These melanocytes aren’t black but the pigment that they produce is black. Because of the difference of the depth and density of the pigment, some moles appear darker, and others lighter. Some moles are flat, while others are raised.
They can appear anywhere on the body, including mucous membranes (such as the lips, genitals, anus, etc).
There are actually no difference between ‘naevus’ and ‘mole’. Naevus is a medical term while mole is used by layman.
As for how these moles form, they can be either congenital (from birth) or acquired later in life. About 1% of melanocytic nevi are present at birth. Most of the moles appear after the age of two. For some people, the number of moles may increase rapidly during puberty. Individuals with a lot of moles often have a genetic predisposition. Acquired moles may also enlarge due to ultraviolet (UV) exposure. Other factors, like hormonal changes during pregnancy, can cause moles to darken as well.
Conclusion: Since moles vary widely in depth and pigmentation, only a medically trained doctor (eg Master in Clinical Dermatology) can accurately assess their nature. Trusting someone with dual expertise in Clinical Dermatology and Aesthetic Medicine ensures cosmetic precision and safety from the very first consultation.