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Acne Glossary

Your acne vocabulary cheat sheet.



A skin disease characterized by one or more types of lesions like whiteheads, blackheads (comedones) and red pimples (papules and pustules). In more severe forms there can be deeper lumps (nodules and cysts). Acne occurs in the sebaceous glands and its attached hair follicles. Acne mostly appears in body regions where these glands and follicles are more prominent: face (most frequent), chest, back, neck, shoulders, and upper arm. Acne usually starts at puberty and can continue for several years. Adult acne is also possible.


In acne, it refers to a product that helps to constrict/shrink the pores (also called toner)

Benzoyl peroxide

It is an effective skin care treatment for helping get rid of mild to moderate acne. It's an ingredient that has antimicrobial properties that works by killing the bacteria (P. acnes) involved in acne, thus improving acne lesions (pimples). It's particularly effective on papules and pustules.


A non-inflammatory (not red) lesion (also called open comedo). It can be flat or slightly raised and skin-colored, except for the center that is darker. It consists of a clogged pore (filled and dilated by sebum, bacteria, and dead skin cells) whose surface remains open to the outside environment. The surface turns black because of melanin or because of a chemical reaction of the plug content with air. If it becomes inflamed, it will develop into a red pimple.

Closed comedo

Also known as a whitehead.


It is the non-inflammatory (not red) type of acne lesions, consisting of a clogged pore. It can appear as a skin-colored little bump (whitehead) or as a skin-colored round, flat or slightly raised, pore containing dark material (blackhead).


A severe acne lesion that consists of a nodule containing pus. It could become infected and painful. In the long run, it could cause scarring.

Dead skin cells

The epidermis renews itself constantly. These cells are the most superficial ones and shed naturally at the end of their journey from the bottom of the epidermis to its outer surface. Inside the pores, they are involved in the formation of plugs (clogged pores).


A doctor who is a specialist in the diagnosis and treatment of skin conditions and diseases.


The deeper of the two layers of skin (epidermis and dermis). It supports the epidermis and contains many components like giving strength and elasticity to the skin. It's involved in many important skin functions, including wound healing.


The outermost of two skin layers (epidermis and dermis), made up mostly of skin cells. The skin cells continually renew themselves, moving from the bottom up to the surface of the skin where they shed. It has various functions, the most important of which is to act as the body barrier against the environment.


The process of removing dead skin cells from the skin surface. It can be done chemically (certain topical skincare medications, chemical peels) or mechanically (scrubs, medical instruments).


Indicates forced removal

Hair follicle

The small canal in the skin where hair grows (sometimes very tiny) and it opens up in a surface pore. It contains sebum from the attached sebaceous gland, dead cells, and bacteria. In unclogged follicles, the sebum flows freely to the skin surface.


Chemical substances in the body that regulate cell/body functions.


An increase in color (darkening). In acne, it often appears at the site of a pimple, after this is gone (also call post-inflammatory), and discoloration can last a long time.

Inflammatory lesion

It is a reddish, inflamed lesion also known as pimple (papules and pustules are examples of these). A pustule differs visually from the papule because it shows a white/yellow head (pus) in the center of the lesion. It is small (usually less than a pencil eraser) and slightly raised, and can be tender to the touch.


An abnormal formation in your pore.


A flat, limited lesion with a different color from the surrounding skin (e.g. hyperpigmented macules resulting from disappeared acne lesions).


They are visible signs on the skin, leaving a discoloration. They may be left from pimples (acne lesions.)


A color produced by specific cells in the skin. It is responsible for hair and skin color. When you get a tan, melanin is responsible for your skin darkening.


An inflamed deep, hard, reddish bump, slightly raised, and larger than a papule or pustule. It tends to be painful and it can often lead to scarring. It is a lesion typical of severe acne.

Nodulocystic acne

A severe type of acne characterized by the presence of several nodules/cysts. These lesions are inflamed, painful, reddish, large, and contain pus; they may often produce scarring.

Non-inflammatory lesion

A lesion that is not red, indicating it is not inflamed. Blackheads and whiteheads are examples of these.

Open comedo

(plural: open comedones). See blackhead


It's is a reddish, inflamed lesion also known as pimple. It is small (usually less than a pencil eraser) and slightly raised, and can be tender to the touch.


see papule and pustule


It's is a reddish, inflamed lesion also known as pimple. It differs visually from the papule because it shows a white/yellow head (pus) in the center of the lesion. It is small (usually less than a pencil eraser) and slightly raised, and can be tender to the touch

Salicylic acid

A common ingredient found in many over-the-counter skin care products, mostly indicated for mild to moderate acne. In this case, it works to break apart dead cells inside hair follicles, which is a fancy way of saying unclogging pores. It can also help prevent new clogged pores from forming.

Sebaceous glands

Skin glands that produce oil called sebum. They are usually attached to the hair follicles, into which they empty the sebum. They are most prominent on the face, back, chest, neck, shoulders, and upper arms.


The oily material produced by the sebaceous glands and it reaches the skin surface through the pores


Elimination of dead skin cells. It's what happens when you exfoliate

Spot treatment

Skin care medications to be used on individual lesions (pimples).


see astringent


A non-inflammatory (not red) lesion (also called closed comedo.) It is a slightly raised skin-colored little bump. It consists of a pore clogged by dead skin cells and oil, and whose surface remains covered by a layer of skin; therefore the plug content is not exposed to air and does not turn black (as in blackheads).

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