In short. Acne is a disease of the pilosebaceous unit: the pore, the oil gland attached to it, and the fine hair that runs through both. It is not a hygiene problem: four processes act together, excess sebum, abnormal shedding of the pore lining, multiplication of *Cutibacterium acnes*, and inflammation. The result is a spectrum from blackheads to deep nodules.
Key points
- Acne starts in the pilosebaceous unit, not on the skin surface.
- Four processes act together: sebum, blocked pore, bacteria, inflammation.
- Hormones drive it; genes set how sensitive follicles are.
- It is not caused by dirt, washing, or any single food.
- Marks fade; true scars change the skin surface and collagen.
What is acne?
Acne is a disease of the pilosebaceous unit, the pore, the oil gland attached to it, and the fine hair that runs through both. Four processes happen together:
- The oil gland produces more sebum than the skin needs.
- The lining of the pore sheds cells abnormally, so a plug forms at the opening.
- Cutibacterium acnes, a skin bacterium that lives on everyone, multiplies inside the blocked pore.
- The immune system responds with inflammation, which is what turns a quiet blackhead into a red, tender bump.
Why does acne appear at puberty and before periods?
Hormones are the engine. Androgens, present in both sexes, drive sebum production and change the way the pore lining sheds cells. This is why acne arrives with puberty, flares before menstrual periods, and can persist into the thirties and forties. Genes set how sensitive your follicles are to those hormones.
What acne is not
Acne is not caused by dirt, by washing too little or too much, or by any single food. It is not infectious and cannot be caught from another person.
What do the different spots mean?
The sequence explains the shapes acne takes. A blackhead or whitehead is a blocked pore with little inflammation. A red papule or a pus-filled pustule is inflammation closer to the surface. A nodule or cyst is inflammation deeper in the skin, and it is the type most likely to leave a permanent scar.
| What you see | What is happening in the skin | What it means |
|---|---|---|
| Blackhead or whitehead | The pore is blocked and there is little inflammation | A comedone, not an inflamed lesion |
| Red papule | Inflammation closer to the surface | An inflamed lesion |
| Pus-filled pustule | Inflammation closer to the surface, with pus | An inflamed lesion containing pus |
| Nodule or cyst | Inflammation deeper in the skin | The type most likely to leave a permanent scar |
| Red or brown mark | Colour left behind by inflammation | Not a scar; fades with time and protection |
| True scar | A change in the skin surface and its collagen | Permanent; control comes first, repair second |
How is acne assessed?
The word acne describes a spectrum, and treatment has to match the position on it. Assessment is clinical and structured. It records:
- Which lesion types are present and roughly how many of each, because comedones and nodules respond to different treatments.
- The sites involved, since back and chest acne often needs a different approach from facial acne.
- How inflamed and how deep the lesions are, how long the problem has lasted, and what has already been tried and with what result.
- Hormonal clues such as irregular cycles or excess hair growth, the products actually being used, and whether marks or dents are already forming.
- How much the acne is affecting daily life and mood.
- The conditions that imitate acne, which have to be excluded before the plan is set.
Marks, scars, and why the order matters
Red marks and brown marks are not scars. They are colour left behind by inflammation, and they fade with time and protection. True scars are changes in the skin surface and its collagen. Acne that is actively creating scars changes the urgency of treatment, because control comes first and repair comes second. Treating scars while new ones are forming is working against a moving target.
When should acne be assessed by a dermatologist?
Acne is chronic and relapsing, no single treatment works for everyone, and visible improvement usually takes eight to twelve weeks of consistent use. A realistic plan names the treatment, the timeline, and the maintenance step that follows. Arrange a dermatology assessment if:
- Acne is nodular, painful, or already leaving marks and dents; early control prevents permanent damage.
- A proper over-the-counter routine has been used consistently for two to three months without improvement.
- Acne is affecting your mood, sleep, or willingness to be seen; that alone is a reason to seek treatment.
Sources
- American Academy of Dermatology — acne: signs, symptoms and when to see a dermatologist
- NICE Clinical Knowledge Summaries — acne vulgaris, including referral criteria
- British Association of Dermatologists — acne patient information
Internal links
Frequently asked questions
What actually happens inside a pore to produce a pimple?
Four processes happen together: the oil gland produces more sebum than the skin needs, the pore lining sheds cells abnormally so a plug forms, a skin bacterium multiplies inside the blocked pore, and the immune system responds with inflammation that turns a quiet blackhead into a tender red bump.
Is acne caused by dirty skin or by food?
Acne is not caused by dirt, by washing too little or too much, or by any single food. It is not infectious and cannot be caught from another person. Hormones are the engine, and genes set how sensitive the follicles are to them.
When should acne be assessed by a dermatologist?
When it is nodular, painful or already leaving marks and dents, when a proper routine has been used consistently for two to three months without improvement, or when it is affecting mood, sleep or willingness to be seen. That last one alone is reason enough.
Risks & Limitations
- Most chronic skin disease is managed rather than cured, and relapse is expected.
- Treatments typically need 8–12 weeks before response can be judged fairly.
- Topical treatment can cause irritation, dryness, peeling and photosensitivity.
- Systemic therapy may require blood monitoring and carries organ, metabolic and pregnancy risks.
- Isotretinoin in particular requires strict monitoring and pregnancy prevention.
- Pigment change is often slow and may be incomplete.
- No treatment works for everyone, and response cannot be predicted with certainty.
When to Seek Care
- A mole or lesion that changes in size, shape or colour, or starts to bleed, itch or crust.
- Fever with a widespread rash, blistering, or rash involving the eyes, mouth or genitals — seek emergency care.
- Rapidly spreading redness, swelling or pain in the skin.
- Facial swelling or difficulty breathing — possible severe reaction; seek emergency care immediately.
- New or worsening symptoms while taking a monitored medication.
References & Further Reading
- American Academy of Dermatology (AAD) — public and clinical guidance
- World Health Organization (WHO) — skin and infectious disease resources
- Chinese Medical Association, Dermatology Branch — clinical guidance
- Cochrane Library — systematic reviews in dermatology
This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.